I quite like German chip carving knives like the one shown here. I bought this one at a wood show, and have never gone out of my way to mail order more. So I thought I'd try to make a knife like this one out of an old saw blade. This one is not even carbide tipped. It was in a circular saw that I bought at a yard sale.
I cut the blade into strips with my plasma cutter. Much faster than using an angle grinder.
I figured it might take me more than one try to get this right, so I cut the whole blade into strips. Or maybe it was because I had so much fun with the plasma cutter!
The blade was made of hardened steel, which is harder to work. So I softened it by heating it red hot in the wood stove. I then dumped the red hot pieces into the ash bucket to let them cool very slowly (ash is a good insulator).
After this treatment, the steel is relatively workable, basically like mild steel.
I then ground the knife shape into it on a bench grinder. I dipped the blade in water periodically, mostly so it doesn't get too hot to touch.
Then it occurred to me - what if this steel is actually high speed steel instead of high carbon steel? So I did a spark test on it. I'm sure it's carbon steel, though possibly with not the highest carbon content. At any rate, if it was suitable for cutting in the form of a saw blade, it should be suitable for cutting in the form of a knife too.
After rough grinding on the bench grinder, I ground the blade a bit smoother on a small wet wheel grinder. I bought this one for a few dollars at a yard sale.
Before hardening the blade again, I center punched and drilled the holes for mounting it to the handle.
A word of caution:
A reader emailed me. Doing this same step years ago, the drill grabbed and the blade spun with the drill, badly cutting his hand.
So clamping the blade down, or holding it with pliers is advisable (not like what I did). Or at least, make sure the blade is oriented so that if it does spin, the knife edge is moving backwards and/or won't hit your fingers.
After that, I heated just the blade part of the knife red hot with a propane torch and quenched it in water. The rapid cooling from red hot causes the crystalline structure of the steel to change to get it hard again, whereas a slow cool will cause it to be soft.
Hardening steel like this can cause it to be so hard that it's brittle. I made another crude knife blade and hardened it the same way, then tried to bend it. I was able to bend it nearly 90 degrees before it snapped, so I figured, this steel isn't too hard for a knife, and I didn't temper it. Tempering the hardness is done by heating the steel to a specific temperature (not red hot) then letting it cool slowly. Basically, like softening it, but not all the way.
The steel looks all black after heat treatment, so I put it on the wet stone again.
After that, I honed it using a leather strop. The leather strop has an abrasive honing compound smeared onto it.
Testing the blade on some very soft cedar. I was able to cut slices off the end grain, leaving a shiny surface. It's actually more difficult to get smooth cuts on softer woods.
Another popular test is to see if you can "shave" with it. This also worked.
Mind you, even a soft steel can be sharpened to a very fine edge and it will pass these tests. The big question really is, how long will it keep its edge? Time will tell.
My knife blade is 1.5 mm thick. This is just a bit less than the kerf on this very thin 6 1/4" circular saw blade that I have.
I put the blade in my table saw (the homemade one) and cut a bit off the edge of some wood.
I then checked that the tang of the knife fits in the shape of the cut that I just made and made minor adjustments to the shape on the grinder.
I made a partial depth, partial length in the middle of the piece that will be the handle.
Checking the fit.
Then, with the blade clamped to the handle blank, I drilled through the holes in the blade to locate where the holes in the knife need to be.
I rough shaped the handle on the bandsaw, first cutting out the shape, then cutting around the edges at a 45 degree angle.
I smoothed the shape on a cheap belt sander (this is also a yard sale find)
I don't have any dust collection on that sander, so I set it up in front of an air filter. A box fan on the other side of that filter pulls air through it.
I'm using finishing nails as "rivets". I softened these the same way as I did with the steel for the knife.
Cutting the nails to be just slightly longer than the width of the handle
Then pounding on the nails to shorten them like rivets.
Brass pins would have been much more suitable, but I didn't have any handy.
Testing the overall feel of the knife. It felt about the same as the chip carving knife I bought years ago.
Pulling the knife through paper. It leaves a nice smooth edge with no tearing.
Having had success with this one, made another blade for another knife. This one turned out better than the first, except I made the mistake of cutting the angle on the end of it the wrong way. The point on the right needs to be facing up, not down for it to fit in a blade kerf. So this one is junk. It's less work to make another blade than try to fix this one.
The blade in my first knife had a slight bit of play in the handle. I later made another knife blade and handle. This time I offset the holes in the handle slightly to pull the tang into the wood more, sort of like a drawbored mortise and tenon joint. I also drilled a few extra holes and roughened up the side of the knife, then filled the slot in the handle with epoxy before inserting the blade. I figure the roughening and the extra holes will help the glue hold the blade.
I don't do much in the way of wood carving. But knives like this are very handy for chamfering the edges of wood, especially around the edges of larger holes and on inside corners.
There are a lot of videos on making big fancy knives on YouTube. Daggers, swords, machetes, bush craft knives, etc. But how much do you use a dagger or a machete on a daily basis? How much "bush craft" do you do? What makes this different is that it's a knife I will use often. So this will be a good way to check it's durability.