In this post I make my first knife, and I do my best to document each step and provide you with the knowledge I had going into it, and also what I learned and how I would have done it differently. As I said, its my first knife, and I didn't do everything in exactly the right order. However, Im arranging this tutorial in the order that makes the most sense if I were to make another knife based on the knowledge I now have. Because of this, some of the pictures may reveal steps that you haven't seen yet. Dont worry, I dont think its too confusing.
Several weeks ago I was overcome by the need to make a kitchen knife. Right away I went online to find a tutorial (like this one), but didn't find exactly what I was looking for. Many websites I found showed how to, say, make a knife out of an old file or saw blade, but I couldn't find a complete, from scratch tutorial that combined all the steps and processes in one place. Through hours of online research I compiled all the different information I needed, and I thought I could make this easier for the next person by arranging all that info here. This is my first online tutorial so bear with me!
Step 1: Designing, Steel Cutting
There are also some differences in the metal itself. First of all I'm using 0-1 tool steel, and the other knives are stainless, but the other knives also have some metal flange things at the front of the handle, a feature thats impossible to create if you are just using a piece of flat bar stock like I did.
Anyway, these are just some things to consider.
Once you have your design, you should order or acquire your steel and wood. I bought my steel from Mcmastercarr.com (I love that website). I got 2" x 1/8" bar stock that was a foot and a half (18") long, I think if was $35. I had some scrap bubinga (the wood I used for the handle) laying around so I used that. Also, just because jargon is cool, the wood pieces for the handle are technically called scales, remember that. For the metal handle pins I used some 1/4" mild steel dowel (you can get this at any decent hardware store).
Using measurements from my full scale drawing, I scribed my knife outline onto the steel with a sharpie. Notice how I got steel that was exactly the right size so i didn't have to make many cuts. NOTE: If you only have one "true" straight edge in your steel that you can use, make this straight edge the blade, not the spine (the spine = flat top edge of knife where you can push down with your hand when chopping watermelon). When you get around to sharpening, you will see why you want as straight an edge as possible for the blade.
NOTE: Before using tools, make sure to wear eye protection, sometimes ear protection, and for this project, often some sort of ventilator or mask. Also I used big thick welding gloves a lot when working with the hot steel and sharp edges.
Cutting the blade out was no problem. I used a hand held angle grinder with a cutoff wheel to make the cuts. NOTE: Steel burns. Dont let that happen to your knife. When you are cutting, grinding, or sanding the steel make sure to have a container of water nearby that you can dunk the whole length of the knife in while working. Do this often, more often then you think. When cutting the knife out, burnt steel is OK if the burn marks dont go past the lines, but if they do, then your knife is already tainted. I stayed well away from the lines for these initial rough cuts using the grinder.
Cutting the handle out was trickier because I couldn't penetrate all the way through the steel without cutting into the other parts of the handle. I got as far as I could into it, then flipped it over and repeated on the bottom. I still had some material to remove though, so I used a mini version of the cutoff wheel on a dremel and cut through the last bit.
Its messy, but it sort of looks like a knife!
Step 2: Belt Sander Rig, Cleaning Up the Rough Cut
To clean up the front of the blade (the curve on the edge and the two angle cuts on the top by the spine) I used a belt sander which I flipped over and zip tied and clamped to the work bench. I dont have a real belt sander like this one, so I had to improvise. I used 80 grit sand paper for this.
You will get very familiar with this rig when you create your knife edge as well, so if you decide to use this inverted belt sander method I suggest making it very sturdy.
To clean up the handle and the back edge of the blade I used a drum sander bit on a drill press, a sanding drum on the dremel, and a bench top grinder.
Step 3: Making the Edge
Handle = part that you grab
Blade = everything but the handle
Edge = bottom part of the blade, its sharp
Spine = top part of the blade, opposite the edge
Scales = wood pieces that sandwich the metal in the handle and give the handle some meat to hold onto
Pins = the metal dowels that go through the scales and look cool (for this knife they provide no structural importance)
Ok now that that is cleared up, its time to start making your edge. The ideal thing to do here is to remove material on the blade so that it starts 1/8 inch thick by the spine, and tapers down linearly so that the width goes to zero at the edge. Duh, right? Actually, its harder then it sounds. Props to you if you achieve this! Mine ended up being about 1/8 inch thick till about half way down, an inch from the spine, THEN it started tapering to an edge. And the taper wasn't even linear (straight line from beginning of taper to edge), it curved. I didn't worry about it to much until I finished it and tried cutting things like onions and apples. Since the blade gets thick very soon in the cut, as apposed to slowly getting thicker as the cut progresses, you have to push a lot of the thing you are cutting away as you cut. This makes it so the cut requires a ton more pressure then it should. SO, if you can, get that taper nice and straight, and make it take up the total hight of the blade.
Anyways, first I marked the centerline of the edge so I knew where to sand to. If you can scribe it right in the metal thats better then what I did. I just used a piece of tape that ran down the entire edge. If you dont put some centerline indicator and just try to guess, your edge will probably end up crooked and not flat. Like, when you put the edge on the cutting board there will be gaps, a.k.a. you won't cut all the way through some parts of the stuff you're cutting. Hitting that centerline on either side with the taper is key! Actually, you dont want to go all the way to the centerline. I left about 1/64" on either side, which gave a 1/32" flat section right at the edge. If you sharpen all the way to a crisp sharp edge, it will be ruined when you heat treat your knife, and then you will have to sand it down and restart.
When using the belt sander to remove material, always point the edge against the direction of the sanding belt. It sounds a little counter intuitive, but this is the way to do it. To reiterate, you want every piece of sand paper that goes by to first sand the edge, and then the spine.
Step 4: Making the Scales
Once I had the rough handle shape in the scales, I drilled 1/4" holes where I wanted the pins (I'm using 1/4" metal dowel for the pins). For the meantime though, I used temporary wood dowels to hold the scales together. I proceeded to drill out the holes in the metal too. I started with a small pilot bit, and moved to an oversize hole so I would have some room to play with when it came to aligning the scales and glueing. If you feel like you already know exactly how you want to align the scales on the metal, feel free to use the proper size drill bit for the 1/4" pins.
The one part of the scales I did sand to final dimensions were the edges where the handle turns into the blade. Since Im going to polish the heck out of the blade, I dont want to have to get sandpaper or abrasives anywhere near it once its done. So, I did all the sanding for that little area before I glued the wood to the knife.
For the pins, I cut lengths of the 1/4" mild steel dowel on the band saw just longer than .75". Then I ground and sanded them to be exactly .75". They fit nicely in the holes in the scales, and will give me a guide after everything is glued up as to when Im done sanding material off of the scales. Once I hit the pins, the handle will be .75" thick.
Step 5: Balancing the Knife (OPTIONAL)
In order to bring the center of gravity (the balancing point) back towards the handle, I added lead to cavities in each scale.
The cavities obviously can't obstruct the pins, so the most obvious place for them on my knife was between the pins. I measured out how big each cavity could be, and computed the volume. The dimensions were something like 1.6 inches long by .5 inches wide by 1/8 inches deep. Remember, you will be taking off material from the sides of the scales but also the edges and corners, so dont make the cavities to big or else when you sand down the edges of the handle to make a round grip out of the square-blocky one you might sand into the cavities, leaving an ugly hole in your handle. Assuming I could fill the entire space with lead on both sides, I would be left with about .1 inches cubed. Multiply this by the density of lead and you get about 18 or 19 grams. Since there are two scales and two potential places to put lead, multiply this by two to get about 40 grams of total extra weight. I used a kitchen scale and a dixie cup filled with water to mimmic the lead, then attached it to the knife where the lead would be to see if that amount of lead would be sufficient. It was! (as you can see in the photo)
I traced out where I was going to remove material on each scale, and dremeled out the correct volume.
The only lead I had lying around my house was in the form of BB pellets. I weighted out about 20 grams (enough for one cavity) and put them in a small metal lid from a can or something, just something to melt them in that won't catch fire. CAUTION: lead is pretty toxic, melting lead is more toxic because of the fumes. Wear gloves and a respirator (and when using the blow torch, safety glasses too).
The lead does not take long to melt, at all. The melting temperature is 620 degrees, which is really low, and especially if you melt little lead pellets, it goes really fast!
NOTE: If you get the can lid or your container to hot, the lead might fuse into the container. This happened to me a couple times
I just used a butane torch to heat the lead.
After much frustration trying to build little molds the same size as the cavity, I found that bubinga is actually durable enough that you can pout the molten lead right in! So this might be a good thing to consider if you plan on making a knife that needs balancing: choose a super dense, strong wood for your scales!
Because of some surface tension, the 20 grams of lead didn't settle all the way into the mold, so I had to hammer it down a little so it would be flush with the surface of the scale, but overall, pouring the lead right into the wood cavity is definitely the way to go!
Step 6: Heat Treating the Blade
The 0-1 Tool steel I got has a rockwell hardness of about B95. The rockwell hardness scale is basically an arbitrary measurement for how hard something is. Or rather, how resistant it is to being dented by a sharp pointy thing. Thats how they measure the rockwell number, they take a big hydraulic press with a super hard point on the end of it, and press it into the material they are testing. The force of the press is always constant, so the depth of the dent left by the pointy thing corresponds inversely to the harness. If the dent is shallow, the material is hard; if its a deep dent, the material is softer. The rockwell number increases with hardness. B90 is harder then B80. The "B" before the number refers to the type of scale it is because there are different pressures and pointy things they use to punch metal vs plastics vs other things. The B scale is what most raw metals are measured in. But most knives and swords and stuff are measured on the C scale, the harder scale.
Like I said, the metal I started with is B95, and we want something between a C55-C60. This is a good hardness for a utility kitchen knife. Hard enough that it keeps an edge, but not to hard that it snaps under pressure, it will just bend and flex a little. As a comparison, cleavers are generally super hard and super brittle with a higher rockwell harness. You almost never have to sharpen them cause they keep an edge forever, but they chip easily. On the other hand, flaying knives are much softer and therefore super bendy, but require frequent sharpening.
Because of the chemical structure of steel, you can only reliably harden steel to its maximum harness. So, what you have to do is harden the knife as much as possible, which makes it about a C65 on the rockwell scale, and then you soften it by tempering it. Its much easier to reliably temper to different harnesses then it is to harden it to different hardnesses.
To harden the steel you must first heat it up to about 1500 degrees F and then quickly cool it down. When you heat it, you are changing the crystalline structure inside the steel, and when you cool it quickly you "lock" that structure in place. If you let the hot metal cool slowly (by, say, just leaving it out at room temperature), then the structure you have created by heating it up will slowly change back into its initial structure: a much softer structure. By quickly submerging the hot steel into something with a lot of thermal mass, like room temperature oil, the steel will cool [almost] to the touch in several seconds. This "quenching", as its called, prevents that crystalline structure from changing back into what it was before, it locks it in place so to speak.
To temper the steel you have to heat it up to about 500 F, let it 'soak' at that temperature for 20 or so minutes, then let it cool slowly. This low-temperature process gives you much more control over how much the chemical structure of the steel changes back into that softer formation, because the steel changes much slower at lower temperatures. Usually one 'soak' at 500 F for 20 minutes is enough to bring the hardness down from a C65 to a C55 or C60.
Just to recap terms:
Hardening is the process of heating the metal up to its lower critical temperature (about 1500 F) and then quenching it which cools it down really fast, this hardens the metal as much as possible.
Quenching metal is when you submerge it into oil or water seconds after you heat it, quickly dropping the temperature and locking the current chemical structure in place.
Tempering is the process of heating the metal up to a much lower temperature (300-700 F for this type of steel) and cooling it slowly, this makes the steel softer.
Ok, now that you know the theory behind heat treating, its time to actually do it!
For the hardening process, you will need a way to heat up the metal to 1500 F, and a way to cool it down. There are several ways to heat up the metal. The best way is to use an actual forge or metallurgy oven. These ovens get super hot and allow you to control the temperature. However, they are kind of hard to come by. If you really want to do it right, and can't find someone with one of these ovens, you can make one yourself by following these instructions: http://www.popsci.com/diy/article/2009-11/build-your-own-propane-forge (just for functionality, you can probably do without all the fancy custom steel pieces and just stack up some certified high-heat cement blocks into an oven shape, and then stick that propane nozzle in).
The second best way to heat your metal is with an oxygen-acetylene torch (oxy torch for short). For the sake of time, I just used my oxy torch, but it is much better if you use a proper forging over. In a forge, there is very little oxygen because its all being combusted to create the heat. This creates a very inert environment for your steel to change its chemical structure in. If you just use an oxy torch, the hot metal can react with the oxygen in the atmosphere and one: build up a lot of oxidation on your blade (which buffs out easily) and two: it can cause the carbon in your metal to react with the air and leave the knife, leaving you with a weaker, softer blade. If you end up doing using an oxy torch, I would recommend using some type of shielding gas like argon or CO2 to even moderately shield your hot knife from the atmosphere. I have a MIG welder so I just used the argon tank from that and sprayed some argon onto my knife while I was heating it. It didn't work perfectly, because my blade still oxidized some, but Im hoping it helped a little at least.
If you are using a forging oven, set the temperature to 1450 F and let your knife soak for about 10 minutes. It should get orange hot.
If you use an oxy torch, just use the regular pre-heating oxygen acetylene mixture, do not add the extra oxygen like you usually do when you oxy cut metal, if you do this you will just cut through your knife! Just use the pre-heating settings and work your way, slowly, length wise, up and down the blade, starting at the spine and working your way towards the edge. This is to make sure you dont overheat the edge. Since the edge is much thinner, it will heat up much more quickly then the rest of the blade, so starting at the spine and working towards the edge will allow you to heat the edge just right.
talk about how you know when its hot enough
talk about quenching
Notes on quenching:
Depending on the type of steel you have, you will either be using water or oil to quench. The difference is water cools the metal more slowly than oil, and some steels prefer different speeds of cooling for this process. Make sure to check which steel you are using before you do this step. When I bought my steel, the package read in huge letters "Oil-Hardening 0-1 Tool steel", so hopefully it shouldn't be to hard to figure out which medium you should quench in. When you actually perform the quench, you are going to want to hold the knife by the metal handle with some big tongs or something so you are guaranteed to get a clean quench on at least the blade of your knife. The blade is where all of this heat treating actually has to work, its whats going to be taking a beating when you use it. The handle is a big thick piece of metal already, and all it has to do is not snap (which it won't, because its 1/8 inch metal), so you could actually get away with just heat treating the blade and not the handle. Thats what I did. I actually clamped a long bar of metal to the handle with a C clamp so I didn't have to worry about holding it with tongs. Then I just heated the blade and was able to pick up the knife with the bar I clamped to the handle. You want the set up to be as fool proof as possible because you only have seconds to get the steel from the heat source into the quenching liquid.
Step 7: Finishing the Edge / Sanding, Buffing, and Polishing the Blade
So, what you want to do is take that 1/32" dull edge down to just before it barely comes together and forms an actual "edge". Leave maybe 1/100th of an inch if you can, because you really dont want to sand past the edge. You also dont want to leave to much material, because you will be sharpening your blade with a whetstone for hours (we will get to that in step 9 though).
Once you have your nearly sharp edge, its time to start sanding the blade.
Note: When sanding and polishing your knife, make sure to sand and polish the part of your handle that meets the blade. This way, when you attach the scales, the metal right next to them will be nicely finished, and not still all raw-steel looking. Dont sand and polish the whole handle though, because this smooth surface will hinder the ability of the glue to stick your scales to the metal, keep the metal of the handle rough!
The sanding process removes material so that there are no deep gouges left in your blade. When I say "deep", I really mean less then a thousandth of an inch, but that much can make a huge difference if you want a shiny finish on your blade. Even a matte finish won't look good if it has scratches that deep. I started with 80 grit sandpaper and sanded by hand for a while, then moved to a 80 grit sanding "flap wheel" on an electric drill to get a nicer finish. I moved to a 120 grit flap wheel, and then started moving up to higher and higher grits, sanding by hand (the highest grit flap wheel I could find was 120). I think I used 220, 320, 600, 1500, 2000, 2500, in that order, spending maybe 5 mins with each grit size. It takes a while, and your hand will cramp. Make sure to keep the direction of sanding the same though! Your finish will look much sloppier if you sand at random, inconsistent angles. I chose to sand from the blade to the spine, making the grain go perpendicular to the length of the knife.
Tip: when getting up into the 600 or 1500 range, it can be a good idea to wet your work piece with a bit of water every few minutes. Most high grit sandpapers are water proof, and lubricating them with water keeps them from getting "clogged" with microscopic metal dust. This lengthens the life of your sandpaper, and can make work faster.
Once you feel like you are done sanding (cause its really up to you how shiny you want your knife), you can either call it a day and move to the next step, or you can polish your blade.
Polishing uses basically the same concept as sanding, but instead of taking off material with little pieces of sand, polish takes off material with microscopic particles. There are different grades of polish, just like there are different grits of sandpaper. I used three grades of polishes, starting with the "coarsest" and working up to the "finest". The polish comes in these hard sticks of... polish, and when you press one up against a spinning polishing wheel it melts and coats the wheel with the polishing substance. The polishing wheels I used where little 3 and 4 inch wheels made of cotton. You need to consider what types of wheels you are using, because finer polishes work better with softer polishing wheels, and coarser polishes work better with firmer wheels. The information to figure all this out should be on the package of the polish stick, and sometimes on the polishing wheel package as well. Just make sure you have some way to tell the polish sticks and polish wheels apart, because its a good idea to only use one type of polish on a wheel.
I dont have an actual polishing wheel set up like this, so I just put a bolt through each wheel and stuck it in my drill chuck. To apply the polish (this took me a couple minutes to figure out) start the wheel spinning and press the stick of polish into the wheel. It will take a few seconds to heat the polish so it starts melting, once it does, keep the stick there for a few more seconds to coat the wheel nicely with the polish. Its good to apply conservative amounts of the Make sure to go with the same grain as you did with the sandpaper, and dont be afraid to push kind of hard. The abrasives in the polish are microscopic, so its pretty hard to permanently damage your blade with them.
Its up to you how much you want to polish your blade, and with how many polishes, etc. I used three, spent maybe 5-10 minutes with each, and the final result was pretty good. I still had considerable scratches that were apparent when held up to the light right, but for the most part it looked pretty shiny.
Once you like the way your blade looks, put some masking tape on it so it doesn't get scratched, and its time to glue the handle together!
Step 8: Assembling Handle / Sanding Scales
First I glued both pins into one scale.
If you remember back to step 4, I left both my scales oversize, meaning they are thicker, longer, and wider then they needed to be. The idea is I will glue them together, then use the metal handle in-between them as a guide as to where to sand down to. Also, once the pins are glued in (which are the correct thickness of .75 inches) I can just sand down the sides of the scales until they are flush with the pins.
So for the glue up, since my scales were still way oversize, I had to do a little bit of calculation to figure out the exact depth the pins needed to be mounted in the scale. For all the glueing I used a Gorilla Glue brand superglue, but I'm sure epoxy or any other super glue would work too (3M has some great products if you can't decide which glue to get).
Next I glued the metal knife onto the first scale with the pins, and clamped it in place.
The great thing about super glue is it dries in about 5 seconds (I think I let it sit for about an hour or two, but still its really fast)
I glued the second scale on and re clamped everything.
Unfortunately, the pins sank a bit while I glued them into the first scale, so they are a little bit to far into one scale, and not far enough into the other scale. Ah well....
Now that the handle is assembled, its time to shape the scales to the metal.
For the sides (the perimeter of the handle with the metal showing) I used a drum sanding dremel bit and sanded the the wood down until I hit the metal.
For the top and bottom of the scales (the faces of the handles with the pins), I put the largest grit sandpaper I could find (60 grit) on my orbital sander, and spent nearly 20 minutes sanding off the wood until I got down to the pins.
Once you are done with the sanding of the sides and the top and bottom, you should have a handle that's the right thickness (mine was about .75 inches), and the wood scales should be matched on the edges to the metal handle sandwiched in-between. Now its time to sand down the edges of your handle to make it less blocky, so it feels more natural in your hand. Careful! If you carved out a cavity for the counterweight, make sure you dont sand into the cavity! You will have a big whole in the side of your scale.
I used the same drum sanding dremel bit to take material off the edges of the scales.
Once the handle feels good in your grip, sand all the wood parts of the handle with progressively higher sandpaper until its as smooth as you want it. I didn't go past 600 grit.
Now you are ready to stain and seal your handle!
Step 9: Sealing the Scales
Sealing the scales makes them waterproof and also brings out the natural grain of the wood.
Before sealing or staining, make sure to wipe your work piece down with a tac cloth or microfiber cloth to get all the sawdust out. You dont want to seal sawdust in your beautiful handle! Wipe down with tac cloth between coats too!
First, I applied several coats of danish oil, then I did two coats of polyurethane sealant.
The danish oil is mainly just to bring out the grain. Bubinga, the wood I used, has really pretty patterns, and the danish oil brings them out and defines them nicely. If you do use some danish oil, make sure to wait 6 hours or so after the last coat before you put the polyurethane on. The danish oil tends to "seep" a little bit even after you wipe it off at first, so just wait a bit to make sure it doesn't seep anymore before you apply the polyurethane (or else bubbles might form in the polyurethane).
The polyurethane is actually what does the sealing of the wood. Its a polymer- based solution, so when it dries it actually creates a plastic-like coating around your handle. Make sure to buff lightly with steel wool and wipe with a tac cloth after it dries and between coats!
Step 10: Sharpening
You still have that 1/100th of an inch or so on the edge of your blade, or, if you sanded it all the way down to the edge, then you have a dull edge. Either way, you need to sharpen the edge with a whetstone.
A typical culinary whetstone (which is what I used) has two sides. One side is a course, porous stone, the other side is a finer stone material. The idea is you scrape the blade edge on the stone at a particular angle, and some material gets scrapped off the metal each time, making your edge sharper and sharper. You start on the coarse side and after a while switch to the finer side. Watch this video for a good tutorial on how to use a whetstone correctly.
Now that you know how to use a whetstone, start sharpening! And keep sharpening. And keep sharpening.... It takes a while. Or at least it did for me. I spend nearly an hour on the coarse side, then switched to the finer side. Periodically, if you take breaks and try to cut things like onions or tomatoes, you will get a sense of how much more you need to sharpen.
Once you think you can't possibly get it any sharper with the fine side, its time to sharpen it with a strop.
A strop is basically a rough strip of leather. I used the back side of a belt and it worked fine. To use a strop, secure one side to something stationary (I used a door knob) and put slight tension on the strop by pulling on the other side with your hand. Then, just like you did with the whetstone, scrape the knife blade across the leather using the same angle (20 degrees or so). Here, the leather is acting as the abrasive material, as apposed to stone on the whetstone. The leather takes off much less material than the fine side of the Repeat this 30 times on each side of the blade, and you should have a sharp blade.
If you plan on eating what you are about to slice up, make sure to wash off the blade before use! There are microscopic metal and stone shavings on it, which could be harmful if ingested.
Step 11: Your Done, Test It Out!
To test it out, try slicing tomatoes or cutting paper like this
I hope this tutorial was helpful! If you have suggestions for edits or just comments in general, please leave them below in the comments section!