File knife questions

I recently picked up a box of junk files and naturally, the first thought that came to me was that they might make good knives.

I took the temper out out of one of them by heating it till it was a dull red, then let it cool. It can now be cut fairly easily with a file.

I have never made a knife of any kind, and so I am not sure where to go from here.

I have a couple of questions to start, and will probably have more as I progress.

1. Since the shape is already pretty much there, do I need to heat and hammer or should I do the final shaping with files? I would think files would be the best way to go, but I don't really know.

2. The file I started with is relatively small, and as I look at it I am thinking I might need to lengthen the tang. What would be the best way to go about doing this, or should I just throw it in the scrap box and start with a longer one?

Any suggestions would be greatly appreciated.


Thanks

I made a file knife a lot the way you are thinking. I first annealed a long file, where there was room for both a grip and a longish blade, then filed away everything else that didn't look like a knife.The taper towards the end of he file blade gave it a nice clipped blade shape after rounding up the lower edge to a point.
As for the tang, I just cut it off behined the grip area I had left and rounded off the stub, and drilled the stub for a lanyard.

Either Nicholson, or Simmonds. I don't trust the others.

I prefer to forge them into their rough shape and then finish them with files, grinders, and stones. Most of the professional knife builders I know (1 Wayne Whitley) say there is something to be gained in edge holding ability by forging a blade. They call it edge packing. Also after you will want to re-harden and then draw it back to 52-56 Rockwell C if you have access to a hardness tester. If not your best bet is to only harden the edge leaving the back soft. A lot of the cheaper files are water-hardening steel. The good ones as mentioned above are usually oil hardening. If you do not know who made it the only way to know for sure is to try oil first and if it comes out soft it is a water-hardening steel.

These are definately not best quality files. No name brands, and the one I started with, is stamped CHINA at the tang.

I paid a dime a piece at a flea market, with the idea that I could just use them as raw steel if nothing else.

I already have that one well on its way to final shaping, figuring if I ruin it it's nothing lost but time and a dime. Learn by doing, and ask questions along the way has always worked best for me.

Do I re-temper before or after I polish?

What color do I heat the blade to before quenching?

I plan on an oil quench to start, my thinking is that too soft is better than too brittle. Is there a particular oil that's best, or should I just use the mud that came out of my '73 Jeeps crankcase?

File and grind to your final form and polish after you harden. The color should should be a cherry red. If it begins to shift to orange it is too hot. Use clean oil to quench otherwise you will get a lot of carbon build-up that you will have to polish off. A torch can be used to draw out some of the hardness if it is too hard. Posish your blade and then apply heat until the clean metal turns a straw color and set aside to cool slowly. Hope yor knife turns out good. :thumbsup:

Forging steel does nothing to improve it. Edge packing is a complete myth perpetrated by those smiths who know nothing of common metallurgy, and do not take time to learn even the basics. Steel is incompressable. It cannot be "packed". The idea behind "packing" is to reduce grain size by breaking up and compressing the grain. This is not possible. The only way to reduce grain size is with heat cycleing, which many smiths are unknowingly doing while they are heating and hammering. It is the heating, and not the hammering, that does the grain refinement. The normalizing process is where the grain gets reduced in size. Heating to a little above critical and cooling until all red is gone, in a triple cycle will reduce the grain about as far as it will go, in common steels. Another myth is that of bringing the steel to critical and immediately quenching to harden. To get the best from the steel it needs to go at least 50o above critical, for simple steels, and often as much as 100o above, and that will put it into the orange color range, red-orange to most eyes, and most common alloyed steels need to soak at that upper temp in order to form a good solution. 5160, and especially 01, are two of these alloyed steels that will benefit from a soak. Another busted myth is the file check for hardness. A file is usually at a hardness of 65, to 65+ Rockwell C scale. Common thinking is that it will cut any other steel softer than that. Fact is, most files will not cut other steel that is harder than 58Rc. So the file may lie as to how hard the steel is after the quench.
As far as testing the steel in an oil quench, to see if hardens, or needs a water quench, if it is case hardened low carb steel, it will not harden with either, and water quenching is always risky when quenching something as thin as a knife blade. There are special quench oils for water hardening steel, although you may get a close enough quench with ATF, or even thinned ATF, to make a usable knife. Nicholson files seem to do very well with thin quenching oils, and hold an edge very well, to excellent, with a triple temper of one hour each at around 425o, to 450o. Just use your home oven with an oven thermometer to be sure of the temps. To harden a Nicholson, bring to red-orange in very dim light, and quench in thin oil, ATF, heated to 125o. move the blade fore, and aft in the quench. Never side to side. Keep this up for about a minute, or a tad longer,and remove it from the oil. Be sure to heat cycle first for your best grain structure. If the blade warps in the quench, you have about five minutes to straighten it with your gloved hands before it takes a final set. There is another way to straighten it later if want to contact me.

Good post. Solid information. Sigh.......I hate it when my long cherished beliefs are doused with cold water.

Ogre

Ogre said:

Good post. Solid information. Sigh.......I hate it when my long cherished beliefs are doused with cold water.

Ogre

Click to expand...

So, does that extinguish them or harden them? With some people it seems to do the latter - they argue all the harder for being wrong :grin:


Hey Wick,
Can you explain what you mean by "triple-temper?" I have run across the phrase before, but thought it was a fantasy phrase to make the sword, etc., sound more impressive. It appears that I was wrong.

When high carbon steel is heated above non-magnetic, it transforms to a condition called austenite, which is simply a rearrangement of the iron, and carbon atoms in their atomic cubicles, and becomes a homogenous solution of iron, carbon, and alloys, if present. When rapidly cooled, the atoms are basicly locked in this new position, and they do not like it. It is not their natural condition. This condition is called Martensite, which is the hard condition of steel, and is under high stress to change back to its room temp condition. In most cases, not all of the austenite is going to convert in the quench, and will continue to form martensite even after the steel cools. This is why it is important to temper ASAP, or the steel may crack. Heating the steel at a temp much lower than non-magnetic will allow the atoms to slip back a bit toward where they really desire to be, and thus relieveing much of the stresses. To accomplish this takes heat, and sufficient time. However, any retained austenite may continue to make more untempered martensite, so it is good to temper again, after cooling to room temp. Testing has shown that after three temperings, retained austenite is at a minimum, and things are pretty much where they will stay. Some of the alloyed steels can get by with one long temper, many of the simple steels benefit with the multiple tempers, so it becomes much a matter of personal choice, and confidence that you have the steel in the state that you want it to be in, which in a blade, is hard, but tough.

I see. Thank you.

Many smiths will do "triple quench", which is not triple temper. They will heat to the austenite condition and quench the blade three times. their reasoning is that this forms smaller grains, and it will, if the steel was not properly normalized before hand. But if the steel has been properly "normalized" before the initial quench, very little, if anything will be gained, other than greater carbon loss in the steel. If the triple quench shows a significant reduction in the grain size, then it was not normalized enough. Normalizing generally consists of a fast, even heat to around non-magnetic, or a bit beyond, then cooling in still air until the red heat leaves, then repeating twice more. If warp occurs, straighten and normalize until it no longer warps. This reduces, and often eliminates warp in the quench also. Normalizing is an absolute must in a forged blade. It negates the damage done to the grain structure that the forgeing has done. It really may not be necessary in a blade from factory spheroidized anealled bar stock, but will reduce any stresses from the grinding of it.

Man,

this is getting way too technical for me.

I'm still struggling with cherry red, orange and straw heat.

OK, I've read these posts.

This is where I'm at:

I have a cheap chinese made file of uncertain alloy. It worked for a while as a file, but was soft enough or abused enough, that by the time I got it, it would no longer cut.

I used a Map Gas hand torch and ran it up to the point that under flourescent light it glowed a dull red. This seems to have worked as far as taking the temper out.

I have not put a hammer to this one. The basic shape and size were already there, and it only took about 2-3 hours to get the final shape done with my good files.

Here's where I'm going:

I still need to clean up the surface with a super fine file, which I will do before I re-temper.

I need to find a better way to heat the blade. The torch, while ok for removing the temper, doesn't put out enough heat to uniformly hold the entire material to a uniform color. I'm thinking a hard wood fire in my fire pit.

Heat to a uniform cherry red. Allow to cool to room temp.

Heat again. Oil quench.

I don't have a hardness tester, so I'm going to have to work with it til I get it where I think it should be.

Too hard, apply some heat, but not enough to get the color.

Too soft, re heat to cherry and requench.


Is that where I need to go, or did I miss something?

You have the general idea. I don't know whether a fire pit is going to get hot enough. A small forge using charcoual or better yet coke would be better. The coke will last much longer than charcoal which burns at a rapid rate when you put forced air to it. If a fire pit is all you have go for it but make sure you have a really big pile of coals. Here is a pic of one I hammered out of a file (Black Diamond I think) 20-25 years ago. It has butchered numerous whitetails.
:wink:

My first forge was a hibachi over filled with charcoal, and a hair dryer for forced air. It worked, but like runnball said, the charcoal burns fast. However, that would get you by for just an occasional blade.

Before you go and invest a lot of time into your project I will warn you that some of the files that are being imported from China, might not actually be tool steel, but rather just a mild steel that has been case hardened. If it is not a high carbon steel it really isn't worth your time and effort to make it into a knife since the end result, no matter how nice the workmanship, will still be a lousy knife.

I used to have my students build knives from files, but now I just order in flat ground 01 stock since I know the material and I also don't have to worry about a student making a bumm knife due to bad material.

Mr. Johnson has a very valid point. I should have mentioned that myself. :v If it were me, and since you have many of these files, I would heat treat one, as is, before wasteing a lot of time and effort to make a blade from one. If nothing else, you will see what you might need to change, or add to, to make things go well. If you can get it hard enough for a good file to skip off of it, without cutting, you can be reasonably assured of making a useful blade from it. What I posted on file testing, is just a fact to bear in mind, when trying for the best. If you can get that file, that hard, you can make at the very least, a usable blade, or even better. As a pro, I strive for the best. Whether I achieve that goal or not, I do my best to do so, with what knowledge, skill, and tools, that I have at the time. I have to answer to my customers, but you have only to satisfy your own needs. If you can get a usable blade, that works for you, then all is well. You will have a tool made by your own hands that you can be justifiably proud of. Whether it be the best or not, in reality, it will be the best in your world, and in the end, that is what really counts. But do test one of those files first, and save yourself some work, and grief, if it will not work out. I wish you the best in your endeavors.
A PS
After you think the test file has been hardened. Put it in a vise, with a couple of inches above the jaws, hit it with a hammer, and see if it breaks, or just bends. If it does not break, it is either low carbon, or you did not get the hardening process right.

Just curious as to how the file knife making is going. :v

Well I was going to try this, grind my shape out and grind off the file checking, heat it up and quench it a couple times in some hot motor oil but now I know I actualy don't know squat about it at all, gee thanks for busting up my dreams :grin: Just kidding, but now I'll just buy one.
Jim

If at first you don't suceed, TRY, TRY, TRY, again. We learn by doing. :grin: