Marking Knives

[Wendell Wilkerson]

Dave,

Alan beat me to it, but I wanted ask whether you heat treated the blades also. Can you please give some details of how you attached the blade to the your handles? Those knives look like an excellent project to start doing some metal work and tool making.

Wendell

[Dave Anderson NH]

Yes, the steel has to be heat treated to harden it so that it will hold an edge. As purchased, the O1 is full annealed so that it cuts nicely with a hacksaw and is easily shaped with files, a bench grinder, or a belt sander, or all of the above.

There are libraries full of books on metalurgy and the techniques for hardening and tempering metals. Unfortunately I don't have the time to make this a life of research- like you guys I'm a woodworker. With a little research, the aid of some data sheets on ANSI O1 steel, and some advice from friends, I found a simple technique.

Smiths, and others used to dealing with heated steel, can tell temperatures by whether the color is red, cherry red, dark red, black red, and a whole bunch of other colors. This is a bit subjective for my taste and it also depends on the light you are working in and whether or not you've been fortunate enough to have someone experienced to point out the colors. Surface pyrometers and all kinds of other gear are also out of the question for most folks.

My technique is suitable for small stuff only since I only have a standard store bought propane torch. I take my workpiece and clamp it in my visegrips as far from the end being heated as possible. I grab a flat bladed screwdriver and attach a medium sized rare earth magnet near the tip of the blade. I put a small metal container with oil (for quenching) nearby for convenience. Things are now ready for hardening.

Set the torch upright on the bench and turn it on. Do not hold it, you'll need both hands for other things very soon. Pick up the visegrips with the blade clamped in place and place as much of the business end of the blade as possible into the flame. Things should be heating up now and slowly the steel will begin to change color and move toward some form of red. In your other hand you have the screwdriver with the magnet. Carefully and slowly bring it toward the heated portion of the steel. You should feel the magnetic attraction. While keeping the steel in the flame, keep moving the magnet toward and away from the steel constantly feeling to see if there is an attraction. AT THE POINT AT WHICH THE MAGNETIC ATTRACTION DISAPPEARS AND YOU CAN TOUCH THE MAGNET TO THE STEEL WITHOUT ATTRACTION THE STEEL IS AT THE PROPER HARDENING TEMPERATURE. Immediately remove the steel from the flame and plunge it into the oil and swirl it around. Congratulations, you have just successfully hardened your blade. To soften things slightly to prevent edge chipping on a striking tool or a cutting edge subject to abuse, wait till SWMBO leaves the house. Place the steel blade on a cookie tray and bake it in a preheated oven for 15 minutes at 325F.

Notes:

1) Protective and safety equipment should be readily accessible: gloves, fire extinguisher, wear safety glasses

2) The loss of magnetism in the steel at the correct heat treating temperature signifies the change in the austenite to marstentite. (sp)

3. Excercise caution-- obviously all this stuff is hot and can burn you badly. Let things cool down before handling.

4. This info is accurate ONLY for O1 or other oil hardening steels. Annealing temps can be different for different thicknesses and grades of steel. Check it out on a data sheet for recommended temps.

5. I will NOT be responsible if SWMBO comes home and catches you using the oven in this manner. You are on your own Bubba.

6. One final note- do not grind or sharpen your cutting edge all the way to a fine edge before heat treating. If you do, when heating the steel you run the risk of burning off the carbon in the steel (decarburizing) and the steel won't hold an edge. Do your final sharpening and honing after all the heat treating work is finished.

[David Klug]

Dave your description of tempering steel takes me back to the days I was in high school and learning to work with the forge. Our first project was to make a cold chisel. I got it all polished up and it looked great. The shop teacher grabbed it with a pair of vise grips, took 4lb forging hammer wacked away at it. About 1/4 in. went flying off the end. He looked at me and said "Klug it doesn't look like you had it tempered properly. Do it again." I did and this time it passed the test. I'll always remember that lesson. I still wish I had a forge to work with because I really enjoyed it.

DK

[Keith Outten]

Dave,

Thanks for the tutorial on hardening, I can barely remember high school shop when I last did any type of real metal hardening and quenching.

The knives are just awesome!

[Marc Hills]

Dave:

Beautiful job, as always. That snakewood handle is really striking, and of course the brass ferrules add a classy touch. Honestly, I don't know why anyone uses regular steel ferrules anymore.

I'll echo Keith's appreciation for the tutorial on heat treating. It is now cut and pasted in my ever growing notes on handtools.

But really Dave, austenitetomarsentite? You might as well have told me that the loss of magnatism is because the heat scares off a voodoo shamen that put a hex on the metal. Frankly I'm surprised you didn't refer to snakewood and Indian rosewood by their latin names.

Oh, and your approach to casual toolmaking is very wise. No sense in ruining a perfectly good hobby.

[Ralph Johnson]

Dave

Very nice work. Any chance you could post a drawing on the knife without the handle. My old eyes cant see much in the photo. also how did you attched the handle to the blade.

thanks

Ralph

[Dave Anderson NH]

Ralph and Wendell both asked how the knife blade was attached to the handle. The handle is drilled before turning to shape on the lathe so that the hole is centered when it comes time to attach the blade. The blade has a shoulder ground into it to preset the maximum depth the shank of the blade will go in. I mix up a small batch of epoxy and with a toothpick fill the hole about half full. I then wipe a small amount on the outside of the shoulder which is covered by the ferrule (only near the top). Slide on the ferrule and wipe then insert the blade to its full depth. Have a cloth handy with a slight bit of acetone on it to remove any overfill which pours out the top or gets on either the ferrule or the handle. See guys, tool making doesn't have to be a high tech endeavor. A propane torch, some simple vise grips, a file or two, a hacksaw, and a grinder and/or a belt sander and the rest is pure woodworking. My explanation will be a bit clearer if you look at the picture below with a yet to be assembled knife.

[David Rose]

Gavin, Dave's method of heat treating is much simpler and quicker than case hardening. It is also much more suited to the purpose as case hardening would soon be removed in sharpening.

David

Dave - your knives are beautiful work; very inspiring. It occurred to me that for the less patient among us (OK, mainly me) it might be possible to get away with simple case hardening for this application? I remember once forging an (extremely) ugly scriber and case hardening it, and it kept its point pretty well when used on steel. Not very purist I realise, but should do the job.