Let's make a knife! I'm not the best knife-maker in the world (having made about 30 so far), but I've been asked to do this anyway. I realize that "How to Make a Knife" is a bit presumptuous. Originally the title was "Knife build along," but I figured I'd get more hits with "How to Make a Knife," so there it is.
My ole buddy, Jeff, wanted me to make some knives for him and his two sons, so he designed what he wanted using AutoCad and sent me a PDF. I printed it out and glued it to a cereal box with 3M spray adhesive, then cut it out with a pair of scissors. I like to glue my designs to cereal boxes because it's easier to trace around something rigid than just a piece of paper. Plus, I can reuse it.
On my first few knives, I just took a thin piece of scrap wood and used my belt grinder and dremel tool to grind until I got a shape I liked, then used that as a template. Since then I've designed knives free hand on paper (Hobby Lobby sells these doohickies to help you draw curves), and sometimes if I see a knife on line that I like, I'll print a picture of it, and copy it. I was leery of doing that in the beginning because some people sell their knives and might not want to be copied. I justified it on the basis that I was giving my knives away to family rather than selling them. Since then I've done a few polls on some discussion groups to see how others feel about having their knives copied. Although a few people were uneasy with it, most people thought it was no biggy because there's hardly a unique design out there. Take the popular Sharpfinger knife design for instance. Lots of people make knives based off that design. Or take the common chef knife. There's basically the French style, German style, and Japanese style, and every other knife is some version of those basic styles. But there's lots of ways to personalize knives, and all I ever copy is the profile, and sometimes I vary it a little to my liking. The first time I copied a knife, it turned out the person I was copying it from had bought one of those mass produced knife blanks you buy at knife supply stores, so he didn't mind at all.
Anywho, here's the design I'm making today (and probably tomorrow).
Pretty simple, huh? That's just a screen shot of the PDF Jeff sent me. He said it's a RainH2O Products design, which is the name of Jeff's company. Unless it's just a big coincidence, it looks like Jeff was inspired by this Kershaw knife.
When I printed it, it was 6 inches, which is what Jeff wanted, but I don't know what would happen if you tried to print this picture. You could just insert the image in a Word document, size it however you wanted, and print it. That's what I do sometimes. I'll even do multiple sizes of the same knife so I can figure out which size I like best.
For this knife, I'm using 1080 steel 1/8" thick I got from Texas Knifemaker Supply in Houston, TX. In the beginning, I ordered steel from Jantz Supply. Other good places to order steel from include New Jersey Steel Baron, Admiral Steel, USA Knifemaker, Alpha Knife Supply, and Tru-Grit (which is also a great place to buy sanding belts). Or, if you want to get all fancy schmancy, you can order Damascus steel from Alabama Damascus. They have a pretty good reputation, but don't get lured into buying cheap Damascus from Pakistan. There's a lot of that on ebay, so beware. I've heard bad stuff about that--delaminations, poor steel quality, etc.
If you browse these knife/steel supply places, you'll see a distinction between carbon or high carbon steel on the one hand and stainless steel on the other hand. The difference is in the amount of chromium. Anything with 12% chromium, and it's classified as a stainless steel except that D2 has 12% chromium and is still classified as a high carbon steel for some reason. As the name suggests, stainless steels are less susceptible to corrosion, so they're more maintenance free than high carbon steels. The term "high carbon steel" is misleading, too, because all steels are high carbon steels. Carbon is what makes iron hard. Iron, by itself, it just iron. But if you add enough carbon to it, it becomes steel. Sometimes stainless steels have even more carbon in them than high carbon steels.
1080 means it's a simple steel (i.e. not an alloy steel) with 0.8% carbon by weight. In reality, 0.8% is a round number, and it can have anywhere from 0.75-0.88% Carbon. Most knife making steel has a carbon content between 0.6% and 1%. It may not seem like a lot of carbon, but it makes a big difference.
Just as salt changes the temperature at which water changes between the solid phase and the liquid phase, so also the amount of carbon dissolved in iron changes the temperature at which steel changes phases. Whereas water has a solid, liquid, and gas phase, iron has different crystalline phases within the solid phase. At room temperature, iron crystals have a body centered cubic (bcc) structure. Just imagine a cube. You'd have an iron atom on each corner, then one in the middle of the cube. That's bcc. Iron with a bcc crystal structure is called "ferrite." It looks like this:
When you get it really hot (and how hot depends on the carbon content), it changes to a face centered cubic (fcc) crystalline structure. That's like a cube with an iron atom on each corner, but instead of having an iron atom in the middle, you have an iron atom on each of the faces. When iron takes that structure, it's called "austenite." It looks like this:
Bcc iron (i.e. ferrite) can barely absorb any carbon at all, but fcc iron (i.e. austenite) can absorb a whole butt ton of carbon. The carbon fills all the nooks and crannies between the Iron atoms. If your austenite has a lot of carbon dissolved into it, then you cool it slowly, that carbon migrates out of the iron crystals, and you get various structures such as pearlite, bainite, spheriodite, etc. If you cool it really fast, though, the carbon doesn't have time to migrate out. It gets trapped in the crystal structure, and as the iron tries to change it's crystal structure, the carbon distorts it, creating a body-centered tetragonal crystal structure, which is called martensite. Just imagine a cube being stretched so you have four long sides and two square sides opposite each other. It looks like this:
The extra carbon that can't escape causes that distortion. Martensite is really hard. I'm going to come back to this subject when we get to heat treating. I just wanted to explain a little how carbon affects iron.
Different types of steel require different heat treatments. Anything between 1077 and 1084 is going to be pretty easy to heat treat, so it's a great steel for a beginner. You can hardly tell the difference between steels in that range because, as I pointed out above, the 77, 80, and 84 are rough indicators of carbon content. Since their allowable ranges of carbon overlaps each other, it's possible for a piece of 1080 and a piece of 1084 to have the same amount of carbon in them. Now, I know what you're thinking. You're thinking, "If it's for a beginner, then it must not be a great steel." But that is false. 1080 is a good knife steel whether you're a beginner or not. It's just easier to heat treat than most other steels.
Except maybe 5160. 5160 is pretty easy to heat treat, too. 1095, which is what I started out with, was kind of difficult, and I wasn't successful my first few times. But don't get the wrong idea. Heat treating isn't always a matter of pass or fail; it's a matter of getting the most out of a particular kind of steel. 10-series steels are just basic carbon steels. They're about as basic as a steel can be. Different elements are added to steels to enhance their characteristics, e.g. to inhibit grain growth, to enhance hardenability, to reduce corrosion, to improve toughness for a given hardness, etc. Spending more money on an enhanced steel doesn't do you any good if your heat treat procedures don't allow you to get the optimum performance out of those steels. That's why it's better, if you're a beginner, to use a steel that's easy to heat treat. It allows you to get the most out of that steel type without spending extra money for features you can't take advantage of because you don't have an expensive Evenheat oven with a Rampmaster controller which allows you to have precise temperature and time controls. Oh, how I wish I had one!
There's a reason for all these differences that I'm not going to go into, but I highly recommend reading Steel Metallurgy for the Non-Metallurgist by J.D. Verhoeven, and if you don't want to pay $95 for a hard copy, you can read a PDF for free. It's excellent for understanding the riddle of steel. It doesn't give heat treat procedures, but it does explain the theory and experimentation behind it all which allows you to come up with your own procedure. If you google "iron carbon phase diagram" and "time temperature transformation diagram," you'll find a lot of useful information for understanding the riddle of steel.
If you search around knife making forums like Blade Forums or Knife Dogs, you'll see people discussing and arguing over heat treat procedures. The reason is because people experiment on their own and figure out what works for them, then tell that to other people. But there is a heinously expensive book called Heat Treater's Guide that does give heat treat procedures for various kinds of steels. Conveniently enough, you can search inside this book with Google books and find what you need without spending $285. I think they must've come up with some of these procedures through a lot of experimentation because some of them are not at all what you would expect just from understanding the theory.
There is, of course, the option of sending your knives to somebody else to heat treat. A really popular place a lot of knife makers use is Peter's heat treat. I've heard negative things about Texas Knifemaker Supply--their heat treating, not their products. Heat treating is part of making a knife, so it doesn't make sense to me that if you want to make knives for the enjoyment of making knives that you'd send it to somebody else to heat treat. I suppose if you were doing it for a living and were just trying to be efficient, it might be worth it, but I've never understood people who buy bow blanks either. I mean if you want to make a bow, then make a bow. Buying a blank somebody else made is just finishing with somebody else started; that's not making a bow. I look at heat treating the same way. But that's just me, and far be it from me to judge what other people ought to prefer doing.
If you're anything like me, then you like the idea of salvaging free steel from other sources because you're getting it for free, and not as much goes to waste. So let me say a few things about that.
The main problem with recycling steel into knives is that you can never be certain what the steel is. Since the heat treating process is peculiar to each kind of steel, you need to know what the steel is to get the optimum performance out of that steel.
Another problem is that sometimes it's not any cheaper than buying steel. Simple carbon steels like 1084, 1095, etc., are really cheap. If you go to a scrap yard, you aren't going to save much if any money on mystery steel. Or, if you buy files at a pawn shop or wherever, you aren't going to save much if any money.
There are some general truths about mystery steel, though, in case you want to go that route, and if it makes you feel any better, I love making knives out of used farrier rasps. So lemme tell you about some sources of steel that you can have some degree of confidence about their composition and some you ought to avoid.
Farrier rasps, i.e. horseshoe files. I googled around a lot about this, and after using it myself, I'm fairly persuaded that most if not all farrier rasps are made of 1095 steel or something very similar. One guy said he actually called a few companies and was told they make their rasps out of 1095. That is an excellent steel. Some people pooh pooh it, but I think the reason they do is because 1095 is a tricky steel to heat treat, and when people are unsuccessful at it, they blame the rasp. A few brands that I think are good for knife making include Heller, Save Edge, Simonds, and Bellota (some people complain about Bellota, but I haven't had any problems with it). If you can find a farrier (a person who trims horse hooves and puts horse shoes on horses), they might be a good source for farrier rasps. Word on the street is that they go through them pretty quickly. I saw a discussion forum where some farriers said they had whole 5-gallon buckets full of used farrier rasps. Maybe you could trade a knife for some. I've been lucky enough by hanging out on discussion forums to find people who will give them to me.
Every other kind of file. I don't recommend using other files for knives because there's no telling what they're made of, and a lot of times, especially with newer files, they are case hardened. That means the carbon is only in the outside layer, and only the outside layer is hard. The inside is soft and can't be hardened. If you want to use a file to make a knife, you should sacrifice a piece of it. Heat it up to a bright red, almost orange, then quench it in water or peanut oil. Then try to break it with a hammer. If it shatters easily, that means it got hard. If it bends, then it's probably junk. I've found used files at pawn shops for a dollar or two each.
Circular saw blades. Some circular saw blades only have hardened steel on the edges, and they don't make good knives because the interior won't get hard. I saw a guy on youtube quenching a bunch of random circular saw blades, and they all successfully hardened. I still think it's a gamble with ordinary circular saw blades. However, those big ginormous industrial circular saw blades seem to make good knives. They are allegedly made of L6, which is a good steel for making knives. I recently made a couple that turned out great, and now I'm sold on them.
Truck springs and leaf springs. A lot of big truck springs and leaf springs are 5160, which is a good knife making steel and easy to heat treat. But you can't really know for sure.
Ball bearings. A lot of ball bearings are made of 52100 steel, which is also a good knife steel. But I don't know whether ALL ball bearings are made of 52100.
Railroad spikes. RR spikes are popular to forge knives out of, but they don't make good knives because they don't have enough carbon. Even the "high carbon" RR spikes only have maybe 0.4% carbon in them. You need at least 0.6% to make a good knife.
Lawnmower blades. Lawnmower blades might make good machetes or big things to chop things with, but I don't think they make especially good hunting knives. I have no idea what they are made of, but I suspect they aren't all made of the same stuff.
Rebar. Oh hell no! Rebar is just recycled mystery steel, so you'd be piling mystery upon mystery. It may be useful to practice forging on if you can get some stuff for free, but it's not likely to make consistently good knives.
It's impossible to look at a steel and be able to determine what it's made of, but there are methods for determining carbon content apart from just experimenting with heat treatment. You can do a spark test. When you're grinding iron, the sparks that come off travel in a straight line like a rain shower. But when it's got a lot of carbon in it, it's more like fire works. Even the sparks have sparks that fly off of them. Check out the sparks from my 1080.
Some people can look at the sparks and guestimate pretty closely how much carbon is in there. One way you might develop such a skill is to get various kinds of known steels and observe the sparks coming off of each of them. Then get unknown steels and compare their sparks to the known steels. Be sure you're using the same thing to grind the different steels, though, because different grinders could create different looking sparks.
Oh, I just remembered one other draw back to using mystery steel. They're a lot more work than bar steel you buy at knife suppliers. When you buy known steel from knife suppliers, it'll already be annealed when you get it. Annealing is when you heat the steel above the austenizing temperature long enough to dissolve all the carbon and convert everything to austenite, then let it cool slowly so that the end result is a really soft steel that's easy to work with. Mystery steel (assuming it's good steel), will be hardened for whatever use it's already put to, and you have to anneal it first. (Actually, you can make a knife from a file without annealing it first, but that's beyond the scope of this build along). Also, you have to do a lot more grinding or shaping with mystery steel. When I make farrier rasps, I have to spend time annealing them, then straightening them, then grinding the teeth off. With bar steel from a knife supplier, I don't have to do that.
Wow. That was quite the diversion, wasn't it? I just figure a lot of people who might be reading this might not have ever made a knife before. I've been struggling for days with how much detail to include in this build along.
There are two ways to shape a knife--forging and stock removal. In forging, you heat it up in a fire and beat it with a hammer. In stock removal, you cut and grind it to shape. For this build along, I'm using stock removal.
Anywho, the next thing I did was use a sharpie to trace the knife on the steel.
Notice how the blades overlap a little. That's because I don't like to waste steel. i don't like to waste anything, really, even if it's free, and even if it's one of the most abundant elements on earth. I'm crazy like that. You have to be careful cutting between those lines, though.
There are different things you could use to cut your knives out. You could use a plasma torch, a metal cutting bandsaw, a water jet, or an angle grinder with a cut off wheel. I use an angle grinder. I didn't used to have one, but after borrowing my brother-in-law's for about a year, he gave me one for Christmas. :-) I guess he wanted his back.
Lemme make a diversion here and stress how important it is to wear eye protection. Hot iron particles are not like cool wood particles. Cool wood particles flying around in the air can do some damage, but hot iron particles can do some damage! So please, wear eye protection. Don't ever NOT wear eye protection when you're cutting or grinding steel. It's also a good idea to wear breathing protection whenever any kind of dust--be it wood or metal--is flying around in the air. I even go so far as to wear clothing protection in the form of an apron because I've burned holes in some of my clothes already.
Angle grinders don't do curves very well, though. You have to make several cuts, sometimes wasting steel in the process to get where you're going. These outside curves, like on the back of this handle, are the easiest.
The closer you get to that line, the less grinding you'll have to do later, but however close you get to the line should be determined by how steady and accurately you can use that angle grinder without accidentally going over the line. It takes a little practice. It helps me to close one eye and aim down the cut-off wheel so I can make pretty accurate cuts.
The inside curves are the hardest. To help, I make a few relief cuts.
Then I come at them from all different directions until I get it mostly cut out.
Then I cut carefully between the two knife blades separating the first knife from the rest of the bar, clamp it with the blade out, and cut that out as best I can.
I guess you could consider the stuff we've done so far as "roughing out the knife," kind of like you might rough out a bow. It still has to be refined. You can do that a number of different ways--files, grinders, belt sanders, etc. I like to start off using the bench grinder because that stone lasts a long time, and I'd rather wear that out than a lot of sanding belts, which cost money. Plus, it's easier to to do the inside curves with my grinder.
The blade gets hot while you're grinding, so I keep a bucket of water near by to dip it in and cool it off while I'm grinding. You don't have to worry about over-heating the blade and ruining the temper while you're doing the initial grinding since you're going to heat treat it and re-establish the temper later anyway. (I'll explain what "tempering" means when we heat treat it later.) So you can wear gloves if you want to protect your fingers from the heat. I still like to do it bare handed so I can feel it warming up and dip it in water before it burns through my glove all of a sudden, which has happened before.
If you get a fancy schmancy 2x72" belt grinder from Wilmont or a KMG grinder from Beaumont Metal Works, you can get a small wheel attachment for it that will allow you to easily grind tight inside curves. A reckon an oscillating spindle sander would work, too. The Wilmont grinder can even be turned on its side to make profiling a lot easier. I have a friend who has one, and I love that grinder. That's what I would get if I could afford it.
The disk sander works well for grinding outside curves and making them smooth, and sanding disks are inexpensive.
I use 40 grits whenever I'm profiling a knife. Then once it's profiled, I go to 80 grit, then 120 grit.
I also use the 4x36" belt sander. Here I'm grinding the blade, but it's especially useful for grinding flat lines, like the back of the blade of this knife.
I also use the elbow of the sander to grind the belly of the handle.
Since I don't have a Wilmont grinder, I use a dremel tool with a sanding drum to do tight curves like the finger guard on this knife.
Lastly, I sand both sides of the blade. This gets the surface nice and smooth, gets rid of the burrs left by the bench grinder, and it also fixes any irregularities. The best way to do this is tape some 80 grit or 100 grit sand paper to a flat hard surface, like a slab of granite or marble. People sometimes give away little slabs of granite on craigslist after installing kitchen counters and stuff like that. I got this one for $10 on craigslist by posting an ad in the "wanted" section. Granite or marble slabs are useful for sanding knives (or anything requiring a perfectly flat surface), for straightening arrows, and for tooling leather, so you should definitely get one.
Spraying some WD-40 on the sand paper makes it last longer. Sanding the sides like this ensures that it'll be nice and flat on both sides. You could do the same thing on a belt sander, but there is a risk that you'll end up with the sides of the knife slightly convex in case the sanding belt curls up on the sides or something.
They make this magnet with a handle on it you can use to hold the knife against the sanding belt or the sand paper, and that makes it a lot easier to sand/grind. I was too cheap to spend $7 on that, though, so I bought four 50 cent rare earth magnets from Harbor Freight and duct taped those to a block of wood. It works very well. Those magnets hold the knife good and proper. It doesn't even come off when I'm holding it against the belt sander. Here I am using it on the sand paper.
If you're not concerned about removing any imperceptible warpage or unflatness, you could clamp the blade to something, wrap some sand paper around a little block of wood, and sand it that way.
I sand that down to 120 grit, and here's what it looks like all profiled.
Drilling holes in steel can be a bitch sometimes, but I've learned a few things that can help.
Before I drill any holes, I mark where I want the holes to be with a sharpie, then use a center punch with a hammer to make an indentation.
That indentation helps align the drill bit so it doesn't slip around and possibly break when you begin to drill.
You can drill holes in steel with ordinary cheap high speed drill bits (i.e. hss bits), but it's much easier with more expensive cobalt bits or carbide bits. Obviously, when you're cutting steel with steel, the cutting steel needs to be harder than the steel that's being cut. Carbide bits are the hardest bits you can get, and you can even drill through hardened steel with it. But they're brittle and prone to break, so you have to be careful. You never want to use a hand drill with a carbide bit because any bending or torquing at all, and it'll break, and considering the money you spend, there'll be weeping and gnashing of teeth. So just use a drill press. I got a bench top drill press at a pawn shop for $40, and it's worked well for several years now.
Cobalt bits are better than hss bits and will cause you less frustration, so I think they are the best happy medium between hss bits and carbide bits. But not all cobalt bits are created equal. After a little research on the good and the bad, I decided to get these Bosch bits. They got good reviews, and they seem to work fine for me. And there's every size you need.
If that's out of your price range, you can use hss bits, but you ought to learn how to sharpen them. There are youtube videos showing how to sharpen them. I have not found it to be all that easy.
When you drill through steel with steel bits, the bit and the piece will both get hot. If the drill bit gets too hot, you'll ruin the temper, making it soft. Once it's soft, it'll stop cutting and start rubbing more, creating more heat. As you press down in frustration, that extra wear will work harden the piece you're trying to drill, making it harder. With a harder work piece and a softer drill bit, you'll just end up using a lot of profanity. I learned this all from experience and questioning people on internet forums. Let me tell you how to avoid this problem.
First, use a cutting oil. This Tap Magic Cutting Fluid is friggin' awesome!
I've tried other stuff, like the oil I use on my bike chain, but it doesn't work as well. This cutting oil provides lubrication which keeps everything cool. It used to puzzle me how you can lubricate and cut at the same time, but my drill bits seem to work better when I use it.
The way i use it is to first squirt a little on the drill bit. It will run down the spiral, then drip onto the steel I want to drill, which is perfect. Then I drill a little hole, raise the bit up, put a little more oil in the hole, then drill the rest of the way. It works beautifully. If you're drilling through thicker steel, just drill a little, and raise it, let it cool, put some more oil in the hole, and repeat until you make it through.
The second thing you should know is that there's an ideal drill speed for whatever diameter you're drilling. The larger diameter, the slower your drill speed should be. You can use google to find out the ideal speed for whatever diameter you're cutting. Since my drill press only has three speeds, I just put it on the lowest speed for pretty much everything. It may not be the ideal speed for every bit I use, but it's hassle free and works for all my drilling needs.
Some people like to start out drilling a small hole, then progressively make it bigger with bigger drill bits until it's as big as you want it to be. I've been advised that that is not good for your drill bits and is unnecessary anyway as long as you use proper technique, i.e. correct speed and good cutting fluid. Check out this thread on reddit where I brought up my frustrations with drilling 1080 steel. A few people on there sounded like they knew what they were talking about, and I got some good advice.
If you try to hold your knife with your hand while drilling it, as soon as the drill makes it all the way through, it'll want to yank it up, spin it around, and try to injure you in the process. One way to avoid that is get a vice for your drill press. It doesn't have to be fancy, and those cheap ones at Harbor Freight will work. As for me, I'm too cheap even for that, so I hold it down good and proper like this:
I know that knife is going to want to pop up when the drill goes through, so I hold it down firmly. So far, so good, but do this at your own risk.
I'm using 1/8" holes because I'm going to use 1/8" diameter brass pins. Although I'm only using two, I drill a few extra holes.
The extra holes do two things. First, they makes the handle lighter, which gives the knife better balance. That's hardly an issue on small knives like these, though. Some people taper the tang of the knife for the same reason, but that's easier to do if you're forging than if you're using stock removal. I don't like to do that anyway because it makes it harder to drill the holes straight, and it makes it harder to glue the scales on.
Another thing it does is help the scales stay glued on. Epoxy sticks better to wood and other epoxy than it does to steel, so if some of that epoxy gets in the holes, it'll hold the scales on more securely.
Before I start this part, I want to show you this picture so you'll know what I mean by terms like "grind line" and "plunge line."
One of the difficulties of making a knife, where skill and artistry come into play, is keeping everything symmetrical, including the grind lines and the plunge lines. These things don't matter much at all if all you care about is function, but they matter a great deal when your knife is being appraised because they affect it's beauty. People also use them as an indication of your skill. I do the best I can in these situation just to avoid embarrassment.
After drilling the blades, they'll have oil on them, so I wipe them down with a piece of t-shirt with some acetone on it. If you don't have acetone, you can use fingernail polish remover. It's the same stuff anyway.
Then I colour the edge with a green sharpie. It's easier to colour it after it's been cleaned with acetone.
Then I take a drill bit that's the same diameter as the width of the blade, I lay them both on my slab of granite, and I slide it along the edge to make a mark.
If the drill bit is not exactly the same diameter as the width of the knife, that mark will be slightly off center. To account for that, I flip the blade over and do it again. If they're slightly different widths, that'll create two lines on the blade, and the exact center of the blade will be between those two lines. In my case, I guess they were exact because even after flipping the blades and doing it again, I still ended up with one line down each blade.
I'm going to use those lines as a guide when I grind my bevels. I want to keep that line in the middle so the blade is symmetrical.
I also want the plunge lines to be symmetrical on both sides. The plunge line is the transition between the flat part of the blade and the bevel where the edge goes. One way to make sure they're symmetrical is to use one of these doohickies that clamps on to the blade.
When you grind the bevels, it acts as a stop when you run up against the edge of the belt and platen.
I'm not going to use this one because it's too wide for these knives, and I can't get it to tighten up.
These are not hard to make. Just get a piece of flat mild steel from the hardware store (or whatever scrap steel you have), drill a couple of holes, and puts some bolts with nuts on them, and clamp that to your knife.
After you put the screws in there, before you put it on the knife, grind the edges together to make sure they're even.
I'm not going to use that one either because it didn't exist when I did this build along. I usually just eyeball it. To help, I make a mark with a different colour sharpie where I want the plunge lines to start.
There are a few different kinds of bevels you can grind into a knife. There's hollow grinds, flat grinds, convex grinds, Scandi grinds, etc. I'm going to do a flat grind on these knives.
There are a couple of ways I know of to do a flat grind. One is to use a flat file, and there's a simple jig you can make to ensure the grind is perfect and the lines are smooth. You use a couple of hose clamps to clamp a flat file to a steel rod. Then you run that rod through an eye bolt screwed into one end of a 2x4 or something. You can adjust the angle of the grind by adjusting the height of the eyebolt. Check this one out. All the ones I've seen have been some variation of this design.
That is an inexpensive way to get excellent grinds, but it's a lot of work. That's why I use a belt sander/grinder. I got this 1x30" one at Harbor Freight for $40.
Notice how I've got that bar clamp on there to keep the grinder from moving while I'm using it.
It's a lot easier to grind consistent lines on a 2x72" grinder because the belt is wider. With the skinnier belt of the 1x30 belt grinder, the knife sometimes rocks back and forth without you being able to tell, and that creates a wavy grind line. Of course that doesn't affect the function of the knife, only the asthetics, but asthetics are important to knife makers and collectors.
Another advantage of some of those 2x72" grinders is that they have variable speeds, which makes it easier to grind without overheating your blade. Things get hot when you're grinding, and I keep a 5 gallon bucket of water next to me to dip the blade frequently while I'm grinding.
It's hard to explain good grinding technique in words, even for somebody as articulate as me. The best video I've seen on youtube to explain good grinding technique is this one by Walter Sorrells of Walter Sorrells Blades.
I recommend watching a lot of his videos because they are wunderbutt.
I started off grinding with this jig by Trollskyy on YouTube.
That's the simplest one I found anywhere. I had a little difficulty keeping the bevels symetrical, though. I used a block of wood for my jig, and maybe it wasn't all squared up, or maybe the table my belt sander came with was wonky. I don't know. But I eventually gave up on it and started grinding free hand. Although it took some practice, grinding free hand is faster and easier once you get the hang of it.
When you grind a curved blade, you want to pull the knife straight across the belt.
When you look at the curved grind line on a lot of knives, it looks like you ought to turn the knife as you approach the end like this.
But if you're wondering how the tip is going to get ground when you're just pulling the knife straight across, I don't blame you because the tip is closer to the back of the blade, which is angled away from the belt. Whatcha gonna do about i??? I've never heard anybody address this, but what I do is angle the knife by pulling the handle toward me as I approach the end.
I don't know if that's right or wrong, but it works for me.
Here's how I hold the blade when I'm grinding it.
At first, it may seem easier to grind one side than it is to grind the other, but you have to be ambidextrous. That just takes some practice. I find it easier to grind one pass on one side, then another pass on the other side.
I keep going back and forth instead of doing the whole grind on one side before switching to the other side. That also makes it easier for me to maintain symmetry between the grinds on both sides.
I'm probably over-explaining this whole thing. The reality of the matter is that once you start grinding, you'll develop a feel for it that's comfortable for you. You may end up holding it differently than I do, depending on what makes it easier for you to grind smooth consistent lines.
Speaking of which, one way to get smooth lines is to hold the knife kind of close to you and rock your body through the grind instead of moving your arms or hands. Walter Sorrells mentions that in the video above.
When you first begin your grind, it's not easy to maintain a consistent angle, but don't worry about it. The thing you should be most concerned about in the beginning is making sure those plunge lines are even on both sides. I don't begin my grind at the plunge line because it's too hard to just set the blade on to the exact place I want to begin grinding. Instead, I put the middle of the blade against the belt, then slowly move it toward the plunge line until it's right where I want it to be. Once I'm where I want to be, then I go back in the other direction and grind out to the tip. Here's what my first grind looks like.
Do the same thing on the other side, then check to make sure the plunge line is even on both sides. If not, it's easy to tweak it at this early stage. If one is farther back toward the handle than the other, then tweak the other until it matches the one farther back. Don't use a lot of pressure. It's easier to control things if you don't use too much pressure. Once those plunge lines are established, it's easier to keep them even because they'll butt up against the platen, which should be even with the edge of the belt.
Speaking of which, the tracking device on my $40 belt grinder doesn't work that well, so sometimes you have to adjust the platen so it matches up with the belt. That can be a pain. It makes it difficult to make tidy-looking and symmetrical plunge lines.
Once you've establish a bit of a grind. . .
. . . it becomes much easier to stay consistent because you can press the bevel against the belt and actually feel that it is laying flat on the belt. Keep in mind that the harder you press against the belt, the harder it is to feel the bevel flat against the belt, the more it's prone to rock, and the harder it is to control your grind. If you're having trouble feeling, then lighten up on the pressure.
Once you've gotten to this point, you can control how far up the blade you want the grind line to go by controlling the pressure. If you want to take a little more off the edge while not moving the grind line, then put a little more pressure toward the edge, and if you want to move the grind line back toward the back of the blade, then put more pressure there and less on the edge. This takes practice, and to be quite honest I haven't fully gotten the hang of it yet, but I'm getting better all the time.
Having a skinnier belt like I do makes it difficult to keep the knife from rocking and creating a wavy grind line. If you have trouble feeling that you're blade is touching the whole width of the sanding belt, you can look at the sparks. If you only see sparks on one side, then it's not grinding the whole width. Just adjust a little bit until the sparks come from the whole width of the blade.
Watching those sparks also helps you make small adjustments. For example, sometimes the width of the edge will get fatter as you approach the plunge line, and you can fix that.
Start grinding somewhere near the middle of the blade, move the blade so that the belt approaches the plunge line, and as it does, adjust so that the sparks concentrate on the edge of the belt that is approaching the plunge line. If you're not careful, though, you can end up with a smiley grind like this.
See how the grind line kind of goes up right at the plunge line? I had that problem a lot in the beginning. The way you avoid that is that while you're approaching the plunge line, you want to put more pressure on the edge of the blade. You do that by twisting a little with the hand that's holding the handle, and adjusting your thumb pressure on the other hand. That'll remove more metal at the edge near the plunge line and less at the grind line so you don't get that smiley face. I have no idea if any of this is clear, but I'm confident that once you start grinding your own knives, you'll figure all this stuff out on your own. Maybe you'll read this over again and it'll make more sense.
Grind until the grind line is almost as high as you want it in the end and until the edge is about the width of a dime. Be careful to keep that line you scribed in the beginning in the middle of the edge as you're grinding. The reason you don't want to go any thinner than a dime is because the thicker the steel is when you heat treat, the less likely it will be to warp. Warping sometimes happens when you quench the blade. That's one reason. Another reason is because if you use a torch like I do or if you use a forge of some sort, the carbon on the outside layer of the steel will get burned away, making it impossible for the outer most part of the steel to get hard. You want to make sure there's enough steel there to grind away so you can expose the hard steel underneath that will become your edge.
I've read that some knife makers don't grind their knives at all before heat treating. They profile their knives, heat treat them, then do all their grinding. But grinding before heat treating is a lot easier and quicker because the steel isn't nearly as hard. Plus, you have to be really careful when you're grinding your blade after heat treating because if your blade gets too hot, you'll ruin the temper. The more you have to grind after heat treating, the more chance there is of overheating the blade and ruining it.
Here's what my grind looks like when I'm done.
I'll raise that grind line a smidgeon higher after heat treat. So far, I've been grinding with a 40 grit belt. Before I heat treat, I grind a little more with 80 grit, then 120 grit, then 240 grit, then 340 grit, then 400 grit. I do four passes on each bevel with each grit. That doesn't remove much metal, but it makes it smoother which in turn makes it easier to clean up after heat treat. I hear tell it helps prevent warping, too, but I don't know how true that is.
Here's all three of them before heat treating.
But before I do any heat treating, there's one more thing Jeff asked me to do. He wants me to put thumb grooves on the back of the blade, so he sent me this checkering file. It's smooth on the sides and cuts 20 grooves per inch.
To use it, I clamp the blade in the vice like this, rest the edge of the file against the vice, and start cutting.
It cuts really easily and just takes a few seconds. Here's how it looks.
The file is only 3/4" wide. To cut a wider thumb groove, you just move the file over a little. The teeth will find their way into the grooves you already filed so you can maintain that equal spacing while you file extra grooves at the end.
This is my favourite part of making a knife even though it can be frustrating. The process basically consists of heating it until it turns to austenite, then quenching it, then tempering it. Before I go into that, though, I want to share some technical information that explains why things are the way they are. This is a very brief summary of some of the information you'll find in Steel Metallurgy for the Non-Metallurgist, hereinafter referred to as "the book." People have been working with steel for centuries without understanding all these riddles, so you can skip this if you want. It will help you later on in life, though.
This here is a carbon phase diagram that shows the effect of carbon content in steel at various temperatures out to 6.67% carbon.
This is a more simplified version that shows the area that we are most interested in--between 0.6 and 1% carbon.
Lemme explain this a little. Over at the far left, you have pure iron (i.e. ferrite) with no carbon in it. At 1420ºF and above, it will be non-magnetic. At 1674ºF, it will turn into austenite. Austenite is non-magnetic at any temperature, but ferrite is only non-magnetic above 1420ºF.
As I explained earlier, pure iron can't absorb much carbon in the ferrite phase. The most it can absorb is 0.02% when it's at 1340ºF. So let's say we've got some steel at room temperature with maybe 0.4% carbon in it. If ferrite can only absorb 0.02% carbon at the most, where does all that extra carbon go? Well, it combines chemically with some of the iron to form Fe3C (i.e. cementite).
Cementite has 6.67% Carbon by weight, which can be figured out by looking at the fact that the atomic weight of Fe is 56 amu (amu = atomic mass units), and the atomic weight of C is 12 amu. Since Fe3C has 3 Fe atoms and 1 C atom, there are 3x56=168 amu of iron and 12 amu of carbon making the total weight of Fe3C 168+12=180 amu. The fraction of carbon in the molecule, then, is 12/180=0.0667 or 6.67%. That's not explained in the book. I'm just showing off the fact that I remember my highschool chemistry. :-)
So anyway, if you've got steel with 0.4% carbon in it, then you've got a mixture of ferrite and cementite. But it's not a random mixture. The cementite exists in pearlite grains.
Pearlite is a new word, so lemme explain that. A pearlite grain is a grain that has alternating thin layers of ferrite and cementite. For some strange reason I don't understand, pearlite always has 0.77% carbon in it. If pearlite is made up of Fe and Fe3C, then obviously the cementite layers are a lot thinner than the ferrite layers. Somehow, pearlite maintains that same ratio of ferrite to cementite in its layers regardless of the carbon content of the steel.
Now let's think about this. If pearlite contains 0.77% carbon and ferrite contains no carbon, then a steel that has 0.4% carbon is going to have a mixture of pearlite and ferrite. The less carbon you have, the more ferrite and the less pearlite you'll have. The more carbon you have, the less ferrite, and the more pearlite you'll have. A steel with 0.77% carbon will be all pearlite and no ferrite.
That 0.3% and 0.5% carbon are probably not drawn to scale. I just wanted to illustrate how the amount of pearlite in steel increases until you get to 0.77% carbon.
So, what happens above 0.77% carbon? If pearlite can only have 0.77% carbon, then any extra carbon has to go somewhere. Well, it just goes into more cementite. Earlier, I explained that all the cementite in steel below 0.77% carbon exists in thin layers within pearlite grains. Well, the cementite in steels above 0.77% carbon exist both in the pearlite and in grains all their own. The more carbon there is in the steel, the more cementite grains and the less pearlite grains. I won't bother you with another illustration, because you're smart, and I'm sure you get it.
Notice on the carbon phase diagram that the more carbon you add to the steel, the lower the temperature at which it turns into austenite until you get to 0.77% carbon, above which adding more carbon raises the austenizing temperature. However, whether you're talking about steels below 0.77% carbon or steels above 0.77% carbon, once you reach 1340ºF, it will begin to transform into austenite. For steels below 0.77% carbon, whenever the temperature is between 1340ºF and whatever the austenizing temperature is for that steel, you'll have a mixture of austenite and ferrite. The closer to the austenizing temperature you get, the greater the ratio of austenite to ferrite until you reach the austenizing temperature at which point it will all be austenite. The same principle holds for steels above 0.77% carbon except that it'll be a mixture of austenite and cementite.
This carbon phase diagram assumes equilibrium conditions. In other words, it assumes that the temperature is not changing or that you reach whatever temperature you're shooting for slowly. After all, the carbon has to migrate around in the steel, and that takes time. The more it has to migrate, the more time it takes for the phase transformation to happen. If you heat the steel up quickly, that effectively moves all the temperature lines up. If you heat up quickly, then hold at that temperature, the lines will effectively move back down until you reach equilibrium.
So, let's say the austenizing temperature for 0.4% carbon steel is around 1440ºF. According to the carbon phase diagram, we should expect that if the steel is heated above 1440ºF, it will be fully austenite. But in reality, if you heat it up quickly to, say, 1500ºF, it won't instantly be all austenite. You have to hold it at that temperature a little while to give the carbon time to migrate.
Since pearlite consists of thin layers of cementite and ferrite, the carbon doesn't have far to travel to get absorbed in all the ferrite layers. Pearlite turns to austenite pretty quickly. That means for a steel around 0.77% carbon (like our 1080 steel), you don't have to hold it above the austenizing temperature very long before it'll becomes all austenite because it's all (or almost all) pearlite. But for 1060 steel or 1095, you have to let the steel soak for a while to convert it completely to austenite because the carbon has to do more migrating.
You might be tempted to think you can speed up the process by heating the steel well above the austenizing temperature, but you don't want to do that. The reason is because if you do, the austenite grains will get bigger and bigger. The bigger the grains are, the weaker your steel will be in the end. Fine grain is good; coarse grain is bad. The higher the temperature is, the faster the grains grow. So you want to raise the temperature to just above the austenizing temperature and let it soak long enough to convert to austenite before quenching.
This is just one reason 1080 is easier to heat treat than 1095--it's easier to convert it to austenite without causing excessive grain growth because there's a wider range of temperatures at which it will fully convert to austenite without the grains getting too big. Another reason is because it doesn't require as fast of a quench as 1095, which reduces the chances of cracking and warping, but I'll talk about that later.
If you do get excessive grain growth, there is a way to fix that. Thermal cycling is heating the steel above the austenizing temperature until it's all austenized, then letting it air cool until it converts to pearlite and whatever else (ferrite or cementite), then heating it back up again, etc. This will turn large grains into small grains. The way is works is that whenever steel changes phases, the new kinds of grain begin growing on the boundaries of the old grains of the previous phase. If your fully austenized 1080 steel is air cooled, pearlite grains will form on the austenite grain boundaries until there's no more austenite. So where you once had one austenite grain, you've now got multiple smaller pearlite grains. I can't remember if the whole pearlite grain turns into an austenite grain when you heat it back up or if the austenite grains form on the pearlite grain boundaries, but in either case you'll end up with smaller austenite grains than you had the first time you heated it up. Then when you air cool it again, and the pearlite grains form on the austenite grain boundaries, you'll get even smaller pearlite grains than you had before. So you can get some pretty fine grain just by thermal cycling two or three times. You can check this out for yourself by playing around with some scrap pieces of steel. If you heat it up to a yellow colour and hold it there a few minutes, then air cool it, then break it in half, you can see with the naked eye that the grain is coarse. And if you thermal cycle it a few times, then break it, you can see that the grain is fine. I've actually done this.
People who forge knives create all kinds of stresses, so before heat treating, they have to normalize their blades to relieve all the stresses. Normalizing consists of heating the blade up until it all converts to austenite, then letting it air cool. Some people do two or three normalizing cycles, which is basically just thermal cycling the steel. It basically undoes all the previous grain structure with whatever distortions or stresses were in them, and makes the steel homogeneous again with fine grains.
If you use stock removal of bar steel like I'm doing in this build along, normalizing isn't necessary. Some people do it anyway just to make sure. Farrier rasps usually have pretty good grain structure, too, but who knows what happens to that grain structure when you anneal them! My files always come out warped after I anneal them in my fire pit. Then I straighten them out with clamps. I'm sure that causes some stresses, so I normalize my file knives before heat treating.
1080 should be heated to about 1500ºF, held at that temperature for a minute or so, then quenched. That would be very easy to do if you had an Evenheat kiln, and they make them especially for knife makers. But they are expensive, and we are poor, so we have to do things a different way.
When I first started making knives, I used a charcoal forge I made out of a brake drum and a blow dryer.
I used galvanized steel, but don't do that because when it gets hot it releases toxic fumes. I found the brake drum behind a brake shop. I've seen a lot of them at scrap yards, but most scrap yards don't let you walk around because they're afraid you'll get injured and sue them. I had to drill some holes in it to bolt on the flange. I attached a blow dryer I got for cheap at the Goodwill with a dryer hose and some duct tape. I burned charcoal or wood in the beginning. The blow dryer provides way more air than you really need to get the fire hot. You just have to blast it with a little air for a few seconds every now and then.
The only problem with my brake drum forge is that it was too small for some of the knives I was making, and it was difficult to get the blade heated evenly. Usually, the tip would be too hot by the time the rest of the blade came up to temperature. It was also time consuming and used up a lot of charcoal.
Now, I use a two-brick forge with a mapp gas torch.
Although propane will get hot enough, it takes longer which means you have to burn more of it. Mapp gas gets too hot, but once you reach the temperature you want, you can just throttle down the flame. So although a can of Mapp gas is more expensive than a can of propane, using Mapp gas is cheaper than using propane because you end up using less of it.
I posted a thread on the Texas Bowhunter forum about how I made my two brick forge, but I'll explain a little here and some modifications I've made since then.
Fire brick is hard to find locally. I was fortunate enough that somebody gave me some. I later found some local sources by googling "fire brick austin tx." It's not as hard to find if you want to have it shipped to you.
Originally, I took two fire bricks and held them together with some angle irons and bolts with wing nuts, as you can see in the picture above. Then I used a 1.75" forstner bit on a drill press and drilled as far as it would go. Then I put a 1.5" spade bit on the drill press and drilled as far as that would go. It still didn't go as far as I wanted.
I took the angle irons off and scraped out the rest with a spoon, using a straight edge as a guide to get the same diameter and blending in the seems.
Then I drilled a 3/8" hole in the back of it. Then I drilled a 5/8" hole in the side near the back pointing kind of up and kind of forward so when the fire goes in there, it swirls around and comes out the front. A little comes out the back, too.
Here's what the inside looks like.
The problem with the angle irons and bolts is that they cause the firebrick to break in half even if you don't screw them on very tight. Firebrick is really soft and brittle. After being frustrated with that, I got this high temperature cement at Home Depot (or was it Lowes?).
It says it's rated up to 1382ºF, but I've had it up to 1600ºF probably, and so far no problems. This works better than the angle irons. I've fired it many times with no cracking, and it retains heat much better, too. I was even able to fix the brick that broke in half.
This is much nicer to use than a brake drum forge because it's a lot quicker, takes up less space, can be done inside my garage, and heats my blades more evenly. Some people put the torch more toward the front blowing back, but I figured since most of the heat escapes through the front that I'd get a more even heat if I had the flames coming out the front. I think I was wrong.
When I first begin heating the forge, I put the torch on full blast, and I put a piece of fire brick in front of the out-going hole, leaving it cracked open a little, because I figure it'll heat up quicker that way.
It just takes a minute or two to come up to temperature. Here it is all nice and hot.
One of the drawbacks to not having a heat treat oven is not being able to get very precise temperatures. They have these infrared thermometers you can use but the ones at Home Depot don't go high enough, and the ones that do go high enough are expensive.
1080 needs to be heated to about 1500ºF and held there before quenching. What you can do is heat it up until it starts to glow dull red. Then start checking it against a magnetic. Remember that it will become non-magnetic above 1420ºF. Once it becomes non-magnetic, take note of the colour. As you heat steel, it'll go from a dull red to a bright cherry red, then slightly orange, then bright orange, then yellow, then white. So keep checking it against a magnet until it's non-magnetic, and whatever colour it is, heat it up just a smidgeon brighter to reach 1500ºF.
I recommend using a scrap piece and experimenting before heat treating your blade. Heat it up to non-magnetic, let it cool, and repeat until you narrow down exactly what colour it is when it hits non-magnetic. It's best to do this in poor lighting. If you do it in broad daylight, you won't be able to see how bright it is, and you'll end up overheating your blade. It's easier to see the colours in dim light. I do this in my garage, and the regular light in there is just about perfect.
When I heat my blade up, I don't leave the torch in that side hole. I find that I get a more even heat if I hold the torch in my hand and spray the flame straight down the blade like this.
Absent a pair of blacksmith tongs, channel lock pliers work just fine to hold the knife. I hold the knife with the edge down. Since it's thinner, it's prone to heat up faster, so I spray the flame down the back of the blade. Sometimes I'll spray down one side, then the other.
It's not just that I want the blade to reach a uniform heat; I also wanted it to all heat up at the same speed. The reason is because when it changes phases, it also changes volume. You've probably heard that metal expands when it heats up and contracts when it cools down. But when steel changes from ferrite/pearlite to austenite, it contracts. (It blows my mind that even though it contracts in the austenite phase, it's still able to absorb more carbon than the ferrite stage. After all, the carbon absorbs by hiding in the nooks and crannies between the iron atoms.) If one side of the steel is changing phases faster than the other side, it could cause warping. Or if one side has converted more to austenite than the other side, it'll definitely warp when you quench it. Ideally, the whole thing would be austenite so that won't happen.
It's not necessary to heat the whole thing, handle and all. You only need to heat the blade, because only the blade needs to get hard. In fact, it's better if nothing gets hard but the edge of the blade which is why some people do differential heat treating, which is beyond the scope of this build along.
Here is the part of the knife that I heat up:
Now don't be mislead by those colours. The camera makes it look brighter than it really is. In reality, I heat it to a bright red colour. It has just a hint of orange in it. Once I get it to that colour, I set the timer on my iphone to 5 minutes and throttle down my flame so as to hold that temperature. It takes a little trial and error to figure out exactly how much throttling that entails. Once I get it right, I just hold it there until 15 seconds or so before the 5 minutes are up, at which time I lose patience and quench it. Soaking it for 5 minutes makes sure it completely transforms into austenite and that all the carbon is evenly distributed. It really does make a difference as I've discovered through trial and error. It hardens up better and it doesn't warp as much.
Quenching is cooling down the blade quickly so as to convert the austenite into martensite. The speed at which you cool it down determines what happens to the steel. All that pearlite/ferrite/cementite stuff I talked about earlier assumes cooling down in air. If you cool it down a lot slower (like 50ºF per hour), it will turn into spheroidite, which is as soft as steel can get. That's called annealing. If you cool it down really fast, the austenite turns into martensite, which is really hard and brittle. That's what you want.
Different steels have to be quenched at different speeds, so they have to be quenched in different mediums. Some steels are designated with an A, an O, or a W, depending on whether they're supposed to be quenched in Air, Oil, or Water, respectively. Simple carbon steels like 1080 and 1095 have to be quenched relatively fast. 1095 is basically the same thing is W-1, which is a water quenching steel, but these designations assume you're using a thicker piece of steel than we knife-makers use. Since we're using thin steel, we don't have to quench it quite that fast. When you quench in water, you risk your blade cracking. It's best to quench in a fast oil.
The best all around oil to use for quenching anything from 1075 to 1095 is Parks #50. It costs $150 for five gallons, though. Ouch! I tried McMaster-Carr 11 second quenching oil, but it didn't work much better than motor oil which sucks. Now, I use peanut oil for 1080, it works pretty well. When I'm doing 1095, I use water or salt water. It's risky, but I've had more luck with that than with any oil (I haven't tried Parks #50).
The thing about quench speed is that if you don't cool it down fast enough, some of the austenite will turn into pearlite, and although the steel might still get hard, it won't get as hard as you might've liked. This is a time temperature transformation diagram for 1080 steel.
Those red lines indicate the start of pearlite formation and the end of pearlite formation. If you cool it down and it crosses that red line, it'll start forming pearlite. If it reaches the other line, it'll all turn to pearlite. If it crosses that nose but doesn't reach the other side, some of it will turn into pearlite, and some to martensite. Ideally, you don't want to form any pearlite. You want to convert as much austenite to martensite as possible, so you cool it off fast enough to miss the nose.
Notice at the bottom that the time scale is logarithmic. That means as long as you miss the nose, you can relax. But to miss the nose, you've got to cool it off to below 1000ºF in less than a second. That's why you need a fast medium. Some steels, like 5160, contain elements that are meant to shift that curve to the right, giving you more time and making it easier to harden. The surface of the steel cools faster than the inside. Steels like 5160 have better hardenability than 10-series steels because even though the inside cools just as slowly, it still converts to martensite because it has more time to miss that pearlite nose.
Oil works best if it's heated up to 90º-120ºF because it's less viscous that way, flows better, and removes heat faster. Water will immediately turn to steam, creating an insulating barrier, and prevent cooling. That's why you have to move the blade around, but you should move it with oil, too.
I put my peanut oil in this metal container I got at Hobby Lobby.
It holds about a gallon. I've seen things at Ikea you might could use, too. To heat up the oil, I heat up a piece of scrap steel or a RR spike, then stick it in there until it feels hot to the touch, but not so hot I can't hold my finger in it. If it's too hot, give it time to cool down. A RR spike will heat it up in no time.
When my knife is ready to quench, I stick it tip down in the oil and either use an up and down motion or a slicing motion. Do NOT use a stirring motion because that'll cause one side to cool faster than the other, and that'll cause your blade to warp. I've had a few blades warp on me. Lately, I've been using a technique that seems to help prevent warping (besides using longer soak times). I keep it in the oil for about seven seconds. Then I put it between two big pieces of flat mild steel and press them together. The steel will cool it off to room temperature in about 30 seconds, and it'll keep it from warping. If you don't have any big flat pieces of metal, then just leave it in the oil long enough to cool it to room temperature. Well, actually, it won't cool to room temperature if the oil is 120ºF, will it? Okay, then cool it for maybe a minute in the oil, then take it out, wipe if off, and air cool to room temperature. If it warps, you can fix that during tempering.
Your oil will probably flame up when you stick the knife in there. Usually it goes out if you submerge the whole knife. With the channel lock pliers angled the way they are, I have yet to burn my hand while quenching. You should keep a fire extinguisher handy in case of any mishaps, but DO NOT pour water on an oil fire.
If you're quenching multiple knives, your oil might get too hot. With my little container, I can quench two knives before it gets too hot to quench a third. After that, I could wait a while to let it cool down, but usually I stick a big piece of mild steel in there to cool it off. That's not as big of an issue if you're using a bigger container of oil. Of course, the bigger your container of oil, the more it takes to pre-heat it, so it's a trade off.
When you quench to room temperature, not all of the austenite will turn into martensite. To do that, you'd need to cool it more in dry ice and acetone or something, which is called cryo-quenching. You gain a point or two in hardness without sacrificing toughness. It's a bigger benefit with some steels than others, and I don't really think it's worth it for 1080.
If you didn't succeed in converting the steel fully to austenite before quenching, or if you quenched too slow, you might still get some hardness out of your steel, but it won't be optimal. But again, this is another reason to use 1080. You could buy more expensive steels that have better qualities, but unless you can heat treat them perfectly, you won't get that extra performance out of them. And you need a heat treat oven to get the optimal performance out of those more expensive steels. If you're doing it like I do, it's hard to beat 1080. It's inexpensive and you can still get the most out of it.
Knife makers typically measure the hardness of their blades on the Rockwell Hardness C scale (HRC or RC). After it's quenched, you want it to be in the 60's, and preferrably close to 65 HRC. According to the book on page 27, you can get 1080 up to 66 HRC, which is pretty hard. You'd think that adding more carbon would allow you to get even harder, but according to Fig. 4:13 in the book, quenched hardness peaks with 1080 steel and drops from there. I guess that extra carbon in 1095 just adds wear resistance.
There are really expensive instruments with diamond cones that when pressed into steel will tell you the hardness. But we must use other means. One means is to run an ordinary file across the blade. Files are usually hardened to around 62-63 HRC. If the file digs in when you run it across, that means it's softer than the file. If it skates across but doesn't dig in, that means it's harder than the file.
A more precise way is to get a hardness testing file set. I got these. They consist of a set of files that are each hardened differently. The hardest is 65 HRC, then 60, 55, 50, 45, etc. To use them, you start with the hardest--65 HRC. If it cuts, then try 60 HRC. If it skates, then your blade has a hardness somewhere between 60 and 65 HRC. Personally, I find them difficult to use because whether they bite in or not depends somewhat on how hard you press down. Even if your blade is harder than the file, the file can still make scratches, so I never really know for certain.
Before you run a file across your blade, there's something you should know. When you heat treat a knife with a flame the way I do, some of the carbon on the surface of the knife gets burned away, making it soft. This process is called decarburization. If you test the hardness, you'll get a false low reading. To get a more accurate reading, you have to grind that surface off. I sand it clean before hardness testing it. I also take a little off the edge since that's what's most crucial.
Decarburization isn't as much of a problem in a charcoal forge as it is in a gas forge. If your gas forge is big enough, you can put a steel pipe in there and put the knife in the pipe, and that'll help. People who use heat treat ovens sometimes wrap their blades in steel foil with a little paper or saw dust to burn away the oxygen, and that helps a lot.
If the subjectivity of a file bothers you, there's one more thing you can do. You can break it. But you don't want to break your knife, so use a scrap piece--maybe one of the pieces you cut off with the angle grinder earlier. Heat it up and harden it just like you would your knife. Then break it with a hammer. If it shatters like glass, then it's plenty hard. If it bends before breaking or bends without breaking at all, then it didn't get hard enough. If you're successful in hardening the scrap piece, then if you use the same procedure with your knife, it should be successful, too.
The harder a knife is, the better it will hold an edge, but if it's too hard, it'll be brittle and prone to chip or break. The less hard a knife is, the more tough it will be, which means it resists breaking by bending instead. But a tough blade won't hold an edge as well. So the trick to heat treating is striking that perfect balance between hardness and toughness.
Freshly hardened steel is too brittle to make a good knife, so it needs to be toughened up, and you toughen it up by tempering it. Tempering involves raising the temperature to break down some of the martensite, relieving some of the stresses. It reduces hardness, but it increases toughness.
The hardness you should aim for depends on how big your knife is and what you plan to use it for. The bigger the knife is, the more tough you need it to be, and the more chopping you plan to do the more tough you need it to be. So you'd want to temper your Bowie, cleaver, and sword at a higher temperature than your skinning knife.
For 1080 and a typical hunting knife, it's recommended to temper at 400ºF for two hours, then take it out and let it air cool to room temperature, then stick it back in the oven for another two hours. That'll give you a hardness in the upper 50's, but that depends on how hard you got it in the first place.
If your knife warped during quenching, you can fix it during tempering. Temper your knife for one cycle, then let it air cool. Then clamp it to a thicker piece of steel, an angle iron, or something with a penny under each end so that when you clamp it, it bends in the opposite direction of the warp. That'll straighten it out for the most part, but if it's still a little warped, then you can grind it flat after that. It'll make your blade thinner but at least it'll be straight.
A lot of people use a toaster oven to temper, and I used to do that, too, until I discovered the toaster oven doesn't heat very evenly, and it cycles through a broad range of temperatures. Now, I use my regular kitchen oven, which is a gas oven and works great.
Kitchen ovens don't have very accurate temperature dials, so it's best to get an oven thermometer from Target or wherever. After getting one for myself, I discovered that my oven was 25ºF wrong. To get 400ºF, I have to set my dial to 375ºF.
Before I temper my knives, I like to clean them up on the belt sander with 80 grit, then 120 grit. After you quench, it'll have a lot of black scale on it, especially if you quench in oil. Once I've sanded all that off, I wipe it down with acetone. Having a clean blade allows me to see the tempering colours.
Tempering colours are cool. Depending on how hot your steel gets, it'll change colours--yellow, straw, brown, purple, blue, gray, etc. This change in color is only on the surface, though. You can sand it right off. When you temper at 400ºF, you should expect to get a nice golden colour, like on Jeff's knives here.
The bevels are black because I didn't clean them up before tempering. I just wanted to clean up enough to be able to see the colour. Notice how on the handles there's a line, above and below which the colours are different shades. That's the first time that's ever happened to me. I think it's basically a hamon. It's the dividing line between the hardened steel on the blade and the unhardened steel on the handle. That's about the dividing line between where I had it heated to an austenizing temperature and where it was below that temperature, so that makes sense.
Don't freak out if your knife turns out yellow with some blue on it. That doesn't necessarily mean your oven heated your blade unevenly. If you used a big kitchen oven, that's almost impossible. It's more likely that there was some oil on your blade, and the oil turned it blue in places. That's why I wipe mine off with acetone before tempering.
Now that your knife is all heat treated and stuff, it's time to put the final grind on it. You have to be more careful during this step than you were when you originally ground the bevels not to let the blade overheat. If your blade gets too hot while you're grinding, you'll ruin the temper. You'll know because your tip or edge will turn blue. There are a few ways to avoid that.
1. Use a fresh belt. I'm using a 36 grit ceramic belt. They last longer than those cheap belts from Harbor Freight. I got it on ebay, but another place to get belts is trugrit.com. This is a pretty aggressive belt, and it allows you to grind the harder steel without causing it to overheat.
2. Dip your knife in water frequently. A safe bet is to dip it after every pass.
3. Grind bare-handed. That way you can feel the knife getting warm and be reminded quickly that it needs to be cooled in water before it gets too hot.
4. Use a slower speed on your grinder. I don't have that option because I don't have a fancy enough grinder. These Harbor Freight grinders are a little fast which makes it hard to use without ruining the blade.
5. Forget grinders and put the final bevel on with a file and one of those jigs I told you about earlier.
If your edge turns blue, you've ruined the temper, and you have to heat treat your blade all over again.
There is an alternative, though. You can just rethink your blade design. Grind off the area that turned blue, and reshape your blade.
If your grinds weren't perfect originally, this is where you can clean them up and make them nice and tidy. I don't have any special techniques other than what I've told you already. It just takes practice. I'm still working on it myself, and I screw up sometimes. If you absolutely cannot make those grind lines look good, just round them over and blend them in. That's basically what a convex grind is anyway. Just be careful not to grind all the way to the back of your blade in the process, although that's fixable, too.
None of this being careful and artistic with the grind lines affects performance. It's all purely aesthetic. It matters a lot if you want to sell your knives, though.
Here's how my final grind looks compared to one of the knives I hadn't ground yet.
You can see how I raised the grind line a little in the process.
I grind until it's about yea thin.
Hopefully you can get an idea from this picture. Some people use calipers to measure, but I just eyeball it. I want to grind until it's almost ready to put an edge on it, which is about this much.
After that, I sand it with the 80 grit belt, then the 120 grit. Keep in mind you're not grinding at this point. You're just sanding. All you need to do is remove the grind lines from the previous grit, then move on to the next grit.
Recall that I had sanded these knives with 120 grit before I tempered. So when I go to the 240 grit belt, I start sanding the sides, too, and the back of the blade. You don't have to worry about the sides around the handle because you're going to sand those when you put on the scales anyway.
After 240, I glue a piece of leather to my platen for a little padding while I go through the higher grits. I don't know why, but having that leather padding on there just feels better. It's hard to explain. Plus, my 600 and 800 grit belts are kind of bumpy, and the leather padding smooths it out. Actually, I ended up buying another $40 belt ginder just so I didn't have to keep gluing on leather and taking it off again. That way, I could use one with a leather-padded platen, and one without. One of them stopped working, though, so now I just change out the platens on the grinder that works.
A lot of people prefer to hand sand their blades from this point on because it looks better. There's this guy named Akey who hangs out on the Traditional Bowhunter's forum whose knives just look amazeballs because of how much time he spends hand sanding them. Check this one out and this one. It takes hours to hand sand knives, but only minutes to machine sand them. It's really easy to screw them up while machine sanding, too.
Here's some tips in case you want to hand sand your knives. Each time you change grits, change the direction you sand. It makes it easier to tell when you've sanded out all the grooves from the previous grit. When you get to the final grit, don't sand back and forth. Start at the handle and pull to the tip. That way you don't have all those little hook-shaped scratches from when you change direction. Also, use some kind of backing for your sand paper. Leather works well, but you can also use a small piece of wood. Watch some videos on YouTube on hand sanding your knives because there are different methods, and some are easier than others.
As for me, I sanded all the way up to 1000 grit on my belt grinder. I got those finer grits on ebay. I go from 240 to 340, then 400, then 600, then 800, then 1000. You can find those higher grits at auto parts stores. You can go as high as you want. You could get a mirror polish with a buffing wheel and some polishing compound, but you should never use a buffing wheel for anything. They're killers. A knife maker in Alaska named Gordon Dempsey who has been making knives for at least a couple of decades if not a few was killed in 2014 in his shop when his buffer yanked a knife out of his hand and hurled it into his heart. I go up to 1000 grit, not because I like shiny knives, but because the smoother the knife is, the less surface area it hass, and the less surface area it has, the less it will rust. But it's not worth it to use a buffing wheel.
Here's Jeff's knives after they've been sanded to 1000 grit.
Notice that the handles are still a little rough. I do that on purpose. I don't bother sanding them past 120 or 240 grit because they're going to get covered by the scales anyway. Besides, the rougher they are, the more surface area they have, and the more surface area they have, the more the glue has to grab onto, so the more secure your scales will be when you glue them on.
I got Jeff's permission to stone wash these blades. It's something new I've only tried on two knives before, but they came out so well I wanted to do it again.
I got some ferric chloride (an acid) at Radio Shack.
They didn't have any at the Radio Shack in the mall. They seem to only carry it in the free-standing Radio Shacks.
I mix that 50/50 with water in another plastic container. You don't want to mix this up in any metal container because it'll eat the metal. Either use plastic or glass, like a Mason jar or something.
I put the knives in there, tip down with enough handle sticking out that I can pick them back up without sticking my hands in the acid. I leave them in there for a minute or two depending on how dark I feel like making it. Then I take them out, rinse them off, spray Windex on there (to neutralize the acid), rinse again, then dry them off with a paper towel.
They'll be almost black when you take them out. If you want them to stay black, don't wipe them dry. Just pat them or use a heat gun. Then let them sit for several hours, and that black will stay on good and proper. (I think this is the third time I've used the phrase "good and proper" in this build along. I like that phrase.) I wiped mine dry since I don't need or want them black. Here's what they looked like after the acid etch.
Again, the hamon shows up where there's a difference in hardness indicating that my heat treat must've gone well. Isn't that neat?
To stone wash them, I cut a piece of 3" PVC sewer pipe that was longer than the last knives I did and put a cap on one end. Then I poured all those glass marbles in there.
I think I got them at the dollar store, but I can't remember. They sell these ceramic triangles at Harbor Freight that are made for their tumblers, but these were cheaper and worked great on my last knives.
I put all three knives in there together, put the other cap on, then wrapped that up in a flannel sheet and duct taped it so it wouldn't come apart. Then I put that in my dryer.
I left some other stuff in there from the last time I did laundry for extra padding. If you don't pad that PVC tube, it'll make a lot of nose in the dryer and might even destroy your drum. This way, it's not so bad.
I put the dryer on "NO HEAT."
I ran it for 30 minutes, and this is how they looked.
Pretty cool, huh? Actually, I'm going to stick them in for another 10 minutes. Here we go.
There. I think that's a little better. Or maybe it's just the lighting.
I discovered through trial and error that the blades stonewash much better when you do them one at a time because then the knives don't rub together, removing some of the black from the etchant from the sides. Here's what they look like when you stone wash them by themselves.
I did that for about 32 or 33 minutes. The reason the plunge line is black is because the marlbes are too big to get in that little crack. Those triangular ceramic things from Harbor Freight will do a better job of getting in there, but I'm okay with this, and glass marbles are less expensive.
Jeff wanted bloodwood for his handles, so I cut out a few pieces from my stash. Bloodwood is a really hard and dense wood. Ordinarily I'd stabilize my handle wood, but I don't think it's necessary for bloodwood, and I have doubts about whether it's even possible.
Let me explain stabilizing in case you're interested. To stabilize wood means to saturate it with a hardening resin. It makes even soft wood really hard and durable so it'll last a long long time. It's done by first drying the wood to almost 0% moisture. I made a little box with a lightbulb in it that gets to 200ºF. I leave my handle wood in there for 24 hours to dry, then put it in a zip lock bag so it doesn't absorb any moisture. Once it's cool, I put it in a vacuum chamber, add Cactus juice, and draw a vacuum. All kinds of bubbles come out, and I leave the pump on maybe four hours until there are hardly any bubbles coming out at all. Then I turn off the pump and release the vacuum. The atmospheric pressure pushes the cactus juice into all the nooks and crannies where the air used to be. ("Nooks and crannies" is another phrase I like.) I let that soak several hours, often over night. If the wood will no longer float, then I know it's saturated. Then I take it out, wrap it in foil, and put it back in my little hot box at 200ºF for two hours or more. And that's it for stabilizing.
But bloodwood is so dense I doubt the cactus juice would penetrate anyway.
Anyway, I use brass rods they have at most hardware stores for my pins. I put the handle wood with the knife next to it and mark the rod a little longer than I need and cut it off either with my angle grinder or my dremel tool.
After cutting it, the ends will always be distorted and won't fit through the hole, so I roll it against a 600 grit belt on my grinder.
That gives me two beveled ends which slide in the holes easier.
Then I put the knife on top of the bloodwood and use it as a guide to drill my first hole.
It's a good idea to put a wooden backing under the wood your drilling so when the drill bit comes out the other end it doesn't cause the wood to chip out. It's also really important to make sure the table on your drill press is squared up. Otherwise, the holes will be drilled at an angle, and they'll be misaligned later on.
Once the hole is drilled, I put a pin through it to keep everything lined up while I drill the second hole.
I put a pin through the second hole and trace the knife onto the handle material.
I draw the front of the scale according to Jeff's drawing.
I cut it in half with the bandsaw.
I write "out" on the outside of the scales so I don't screw up later.
I grind the bandsaw tool marks off of the insides with my belt sander.
Then I pin the two pieces together and cut it out with a bandsaw, being careful to stay outside of the lines.
Sometimes my pins don't fit. They need to be tight, but not so tight they won't go in without a hammer which could either cause them to bend, in which case they'll never go in, or cause your wood to chip out or split. When that happens, I press it against my grinder with a 600 grit belt and roll it with my camera hand (not shown).
This takes off very little brass at a time. I just keep checking until the pin will go in. You don't want it to be loose or for there to be any gaps at all, though, which is why I use a 600 grit and check it often.
I don't worry about shaping the handle at this point or even sanding to the line except the front of the scales. The disk sander works great for that.
It's important to sand and finish out that front part now because it'll be nearly impossible to do it after it's glued on without scratching up the blade of the knife. So I sand it down to 320 grit.
And it comes out as smooth as an android's butt.
Before glue up, I wipe down the knife with acetone to get rid of any oils, and I put my drill bit through those extra holes to make sure they're open. Here is the glue I use.
If you're new to this, five minute epoxy could cause you to panic. You might be better off with 30 minute epoxy to give you more time. Generally, the longer it takes an epoxy to cure, the stronger it is, but this epoxy I'm using is stronger than some 30 minute epoxy, so I use it.
I lay everything out in some logical fashion to reduce the chances of me screwing something up. Then I mix up some epoxy in a Dr. Pepper bottle cap. I have a bunch of those.
I couldn't take pictures during glue up, but basically, I slathered glue on one of the scales, then a little glue on the pins, and pushed them through the scale. Then I slathered glue on one side of the knife, stuck it on the scale, and pushed the pins through a little more. Next, I slathered glue on the other side of the knife, making sure the glue filled those extra holes, and I slathered glue on the other scale. Finally, I stuck that scale on, push the pins the rest of the way through, and clamp it up.
No, I did not peen the pins. You don't want to use a crazy amount of pressure because that'll squeeze all the glue out. At this point, some of the glue will squeeze out the front of the scales onto the blade. Wipe off what you can with a piece of a t-shirt. Then wet another piece of t-shirt with acetone and wipe some more. The glue will come right off.
I use a lot of t-shirt when I make knives. If you're low on t-shirts, start volunteering at triathlons, half marathons, and things like that. That's a great way to get a free t-shirt.
Five minute epoxy takes five minutes to begin to harden, but it takes a few hours longer to harden good and proper, so I give it the time it needs before I start shaping the handle. Sometimes I don't do it until the next day because if the glue is a little gummy, it'll gum up my sanding equipment. If I wait until the next day, it'll be good and hard.
The next day, I cut off the brass rods with my angle grinder.
Then I ground them flush with my belt sander.
Then I ground off the overhang with the disk sander.
I even did the inside belly curve. I got close anyway.
I went the rest of the way with my belt grinder with a 40 grit belt. If you glue a piece of leather onto the platen, it pads it a little so you can do those inside curves like this.
You can't do that finger guard, though. It's too tight. I tried using a drum sander in my drill press.
But that didn't work out well, so I went back to the dremel tool. No picture. :-(
I used my belt grinder and an 80 grit belt and the leather padding to sand the spine so the wood and the blade are all nice and flush with all the tool marks from the 40 grit belt out.
I went all the way up to 600 grit. doing that.
I couldn't do that with the belly side, though. Remember earlier when I said it's hard to use the dremel tool with a drum sander without there being little bumps? Well, I mentioned that on Facebook, and somebody suggested using a flap sander. So I went out and got an 80 grit and a 120 grit flap sander for my dremel tool, and that worked pretty well.
You could also wrap some sand paper around a wooden dowel, and do it like this.
This would be so much easier if I had a 2x72 inch grinder with a small wheel!
You can shape the handle any way you want. For me, this is the easiest part of making a knife. Jeff was really specific about how he wanted his scales done, though. He wanted them 3/16" thick, flat on the sides, and the corners rounded over. Mine were a little thickesh, so I ground them down close to 3/16" on my belt sander with a 40 grit belt. Then I took off the corners with my belt grinder.
I blended them in and rounded them the rest of the way with a piece of used sanding belt.
The rest is just sanding. If you try to sand over the pins with your thumb as a backing or even a piece of leather, it could cause there to be a bump where the pins are because if the wood around the pins is softer than the pins, then it will get sanded down more. To keep that from happening, I wrap my sand paper around a piece of wood with a flat surface.
When I sand the corners, I wrap the sand paper around a piece of leather. Here's what it looks like after sanding to 400 grit.
People use all kinds of stuff for a finish. Tung Oil seems to be pretty popular. I frequently use super glue. Superglue makes an excellent finish. If you get the thin "liquid" kind, it'll get down in the pours and seal it up nicely. It burns the eyes and nose, though, so I wear goggles and a respirator. I squirt a little on the blade and wipe it quickly with a t-shirt. You don't have much time because it dries fast, but as long as you keep the t-shirt moving, you should be alright. If it doesn't go well, just steel wool and try again. I put on three or four coats.
If you're using stabilized wood, you may not have to put on any finish at all. I do, though, because I figure it's better to have it and not need it than to need it and not have it.
For Jeff's knives, I'm using the same finish I put on my bows. It used to be called Thunderbird, but now it's called Kwick Kleen. According to the web page, it starts out as a lacquer, but then by some kind of sorcery, it turns into a polyurethane. Polyurethanes are more durable than lacquers, but lacquers dry more quickly, even on oily woods, so this is the perfect finish. I put on four coats, usually within an hour. After about six hours, it will have turned into a polyurethane.
You'll want to mix it in a jar with 80% of the Kwick Cleen, and 20% of the thinner that goes with it. When doing my bows, I spray it on with a Preval sprayer, but when doing my knives, I wipe it on with a piece of t-shirt. Here are the three knives drying after the first coat.
I don't see any way of putting the finish on the front of the scales without getting a little on the blade. I suppose you could tape it really close, but that's not easy because of the curve. So I just live with the fact that it's going to get on the blade. Once the fourth coat is dry, I clean the blade with some acetone. Of course it's hard to clean the blade with acetone without also taking a little off the front of the scale. I don't have a solution for this conundrum, so I just do the best I can. I'm open to ideas. Maybe one could put the finish on the front of the scales before gluing them on in the first place, then not have to worry about them later.
Here they are after the 4th coat dried.
To do the edge, I put an 80 grit belt on my belt grinder and grind a secondary bevel, roughly at 20". I go back and forth on each side until there's an edge. I can tell there's an edge when light stops bouncing off of it. Then I go to 120 grit, give it 4 to 6 swipes on each side, and work my way up to 1000 grit. By then, it's pretty sharp, but I go one step further and strop it.
I made that leather belt to go on my belt grinder so I could strop that way, but I've since then taken to doing it by hand like this. I put some green compound on there I got at Harbor Freight. I do 10 or 15 swipes on each side, alternating sides as I go. By then, it's sharp enough to shave hair.
I ran out of hair on my arm, so I had to use my leg. I'm sorry you had to see that.
Some people have a problem with using a belt sander to put an edge on a knife. You could use that file jig I told you about earlier. Using a jig will make it easier to get precise angles and tidy bevels. They actually make a jig called the Edge Pro for sharpening knives. You can get them on Amazon, too. Here's Dan Thornburg of DT Knives who made his own and shows how he uses it to sharpen his knives:
If you're not against belt sharpeners, they make belt sharpeners you can use to sharpen knives, scissors, or whatever. I saw a guy demonstrate one at a gun and knife show last year, and it seemed to work pretty well. I've also seen them at Cabelas.
I used to sharpen my knives by hand. I'd just wrap sand paper around a piece of leather and sand the edge, going all the way up to 2000 grit. I could get them pretty sharp that way, too, but I cut myself sometimes.
Speaking of which, if you plan on making knives, you should have some band-ades. I'm just now getting to where I don't cut myself with every single knife I make.
Stainless steel knives are relatively maintenance free, but high carbon steel, like these knives, are not. There's a few ways to protect them from rusting.
1. Oil them. I used to use Eezox because there were some threads on some discussion forums where people tested several different things to protect high carbon steel, and Eezox always came out on top.1 But then I started wondering if it was safe to clean deer with since the blade contacts the meat which we eat. It turns out that Eezox has some toxic chemicals in it. A little further reading revealed that said toxic chemicals evaporate when the Eezox dries, and it becomes food safe, but I'm still uncomfortable with it. Now, I use mineral oil. Almost any kind of oil will give it some protection. It's just a matter of degree. One of the best food safe oils out there is called Frog Lube. I haven't tried it yet, but I've heard lots of good things about it. Other food safe alternatives include Tsubaki Oil, which I hear tell Japanese chefs use, and Super Lube.
2. Put a patina on them. A patina is a layer of corrosion on the surface of the knife. It inhibits further corrosion. It seems that there are different kinds of rust. There's the red iron oxide that we're all familiar with, but then there's the brown/black oxides. I don't know what the difference is chemically, but you want to avoid red rust as much as possible. The brown/black stuff actually protects the blade. You can force a patina on your knife with some mustard, vinegar, or just by cutting vegetables over time. You can make some cool designs with mustard patinas. Here's a mustard patina I put on a cheese knife I made for my sister. A high carbon steel blade will eventually acquire a patina anyway. I've already acid etched these knives, so there's no point in me forcing a patina on them.
3. Don't store the knife in the sheath. You really only need to put your knife in the sheath when you're carrying it. If you're going to leave it sitting for long periods of time, don't leave it in the sheath. The leather in the sheath will absorb moisture, which will cause the blade to rust.
Here's all the knives with their sheaths.
There ye have it. Ordinarily I would put a build along on multiple pages so you don't have to load so many pictures, but I don't think anybody uses dial up anymore, so I figured I'd put everything on one page for a change.
Here's a really good build along by Ryan Minchew. It's got some nice pictures of his knives toward the end of the thread.
This is another really good build along by Nick Wheeler. This is one has a LOT of detail.
The $50 Knife Shop by Wayne Goddard. I haven't actually read this book, but I've heard good things about it.
The Complete Bladesmith by Jim Hrisoulas. I have read this book, and it is excellent. It has one chapter just talking about different kinds of steel and what they're made of.