File the Knife – BushcraftUK

Another obvious source of steel for knives is a humble file. Most files are made from high carbon tool steel and can be used to make good cutting tools.

That being said, in some cases you may find files that are case hardened only (i.e. high carbon only on the surface/teeth and soft mild steel in the core).

The easiest way to tell which file you have is to put it in a vise sticking out a few inches and tap it with a hammer. However, we recommend wrapping the tape first to catch debris and reduce the risk of scratching from debris.

Fine and hard file

If the file breaks cleanly, you win, but if it does, throw it away. Also note that you need to do this on the working end of the file, not the core. This is because the core remains soft and can bend in either direction.

Most people get their old files from car boot sales or from forgotten toolboxes and other rusty tools in their sheds. Once you know the name of the manufacturer, you can quickly find the right brand to choose, both as material and for actual use (although second-hand files are half dead at best from the start, so I never buy them). no). Some of the most common suitable files that exist (in the UK) include Vallorbe, Grobet, Nicholson, Bacho, Oregon and Sandvik. I mostly buy his Vallorbe files so I end up recycling them.

good file
good file

Assuming you have the right file, you need to decide how to shape it into a knife: forging, normal stock removal, and careful stock removal.

Forging is the most versatile method and allows you to make the most of the materials available.

forged files

If you forge an old file, you do not need to anneal it first, but always remove the original hardness before forging to avoid breaking the tongue end while forging the hot end (fire the file). (just heat it up) each part will turn a dull red).

Also, especially for files with very large teeth or coarse files, it is advisable to grind any teeth that fall near the cutting edge. Simply shoving it into the edge creates a “cold shut” that acts as a stress point and can later become the focus of a crack.

Grinding of teeth near edges

Rasps are generally made of very high carbon steel (1% or more) and overheating should be avoided during forging. Try to keep red and orange. A very bright orange or yellow color is much more likely to cheesy and crumble with a hammer.

The shape of the file doesn’t matter either. For example, I used a round chainsaw file to make some nice looking knives. Simply flatten the blade section and the rest can be rolled, snaked or knotted.

old file

Stock removal is the best way to preserve the pristine nature of your files without damaging your teeth. Of course, you’ll be limited by the size of your starting stock, but most flat files under 8 inches work great as small knives (larger files are fairly thick).

If only hand tools are used to make the knife, the file must first be annealed. The easiest way to do this is to light a small campfire and stick a file in it to heat it up. Steel is usually fine to work with until it turns dull red, but ideally it should be just over non-magnetic (medium orange), cooled slowly, and preferably buried in wood ash. increase. /sand/vermiculite.

If you have a forging kit or other heat treatment kit, use that instead. In any case, it should be re-cured afterwards. If it’s too hot or very uneven, it can cause particle growth and air-cure (embedding in insulation to prevent air-cure) issues that will need to be addressed later. After the file is annealed, it can be treated like any other stock steel.

My first few knives were made with an old file, but there is a perverted pleasure in sanding with a good file. You can use the tools you have on hand to drill, sand and polish.

You can use a good grinder (like a knife maker’s belt grinder) and if you’re careful, you can do all the grinding while it’s hardened. I often use this method when turning files into knives. Temper the file to reduce it to a suitable hardness for your knife, and carefully grind the chamfer of the blade to avoid overheating and destroying the temper. This takes practice, but practice makes perfect.

Abrasives don’t really care if the steel is hardened or not. In fact, hardened and tempered steel is often less “rubbery” than annealed steel, making it easier to grind. The key is to use SHARP abrasives and not the dull belts you probably threw away long ago. Light touch, especially fine particles are good. Still, I tend to use a coarser grit, letting the sharpening abrasive do the job of cutting rather than just scraping the steel. If the blade gets hot, soak it in water to cool it down, and be careful when working on the edge or near the tip. Since you hold the blade with your hands instead of using a jig, you don’t feel heat generation, so I think it’s easier to do. If there is even a little bit of bluing, the area cannot hold dominance at all.

Do not overheat the tip when sharpening

The core part can be further tempered by heating it with a torch until a gray oxide forms on the surface. This further reduces the possibility of cuts and allows you to drill holes for pins and lanyards.

Heat treatment. As with all recycled materials, this will always be a case of best guess and experimentation. The fact that I’m only buying his Vallorbe/Grobbet and Oregon files means I’m looking at what works with those files and feel more confident in the results than randomly picking old files. means that That said, most files are simple alloys and high carbon, so it’s a fairly simple heat treatment that can be done at home without fine temperature control. Aim for 800°C (dull to medium orange, just below non-magnetic) for hardening and quench in lightly heated oil. Many of the very old files were quenched in salt water (file manufacturing plants would transport the salt water rather than try to duplicate it when moving factories). However, if you do choose to try this out, I would recommend lowering the quenching temperature to avoid warping and deformation. crack. Most knives are tempered to a perfect gold or straw, but brown is fine too. Note that the actual temperature is 200-220°C. For example, a normal Vallorbe file re-quenched at 220°C has a hardness of 60RC.

Of course, knives aren’t the only way to work with old files. I have some woodworking tools that I easily made with them (make sure you temper the parts you aren’t working on so they don’t crumble in your hands the first time you use them!). I also have a center punch made from an old file, a wood carving chisel, a metal cutting chisel, a scraper, a draw knife, and a variety of improvised specialty tools that I make in the middle of a job and put back in the file pile. I sometimes make files for living history, and the chisel I made to cut its teeth was made from an old file (just because I thought it was appropriate).

tool from file
tool from file

A few years ago I was lucky enough to visit the wonderful Museum of Tools in Troyes, France. Their collection features large displays of old files and tools made from files. It contains all sorts of things, not just those mentioned above, but bill hooks, knives, axes, scissors, and more. In addition to turning the rasp directly into another tool, it can be a useful source of high carbon steel if you can forge weld it. You can easily fire weld the edge of an old file to a mild steel ax head, re-steel a chisel, or sandwich a file between two bits of low carbon iron/mild steel to form a laminated blade such as a knife. can. ,Such.

Oh, and files make great fire steel for striking flint.

Photo of Dave Bad Knifemaker

Dave Budd is a world-famous blacksmith who specializes in historic weapons, tools and other period ironwork, and runs courses in the rural forests of Devon, especially in the making of knives and axes.
You can see some of his work and get in touch via his website

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