Grinding knives from files, lawnmower blades, etc.

[Highsmith]

Does anyone here grind knives from files, chainsaw blades or lawnmower blades? I have seen pictures of people putting the file in a vice and grinding with a handheld grinder, but wouldn't it be easier to have a mounted grinder and hold the metal being worked?

[egon]

I've heard of people doing it but it has never appealed to me. [img]/forums/images/icons/grin.gif[/img]

Egon [img]/forums/images/icons/grin.gif[/img]

[Bird]

I've never done it myself, but my parents lived in Alaska from 1965 to 1971 and Dad was given a "knife" for skinning moose and caribou that he said held an edge well. It looked like a piece of junk that was supposedly an industrial file that had been ground down to an edge, very thick, still had the file appearing ridges opposite the sharp edge and the handle was nothing more than a lot of black electrical tape wrapped around a part of the file that wasn't sharpened. Sometime in the '70s, Dad gave it to me, although I had no use for it, then in the late '70s or early '80s, a friend and neighbor saw it, asked about it, and took it home to do what you just asked about, then returned it to me after he ground it down, added a tang, riveted a handle on it, etc. So it now looks much like a big Bowie knife. I think he did much of the grinding on a bench grinder.

So I still have it, and still have no use for it. [img]/forums/images/icons/laugh.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Yeah, that was the favorite thing to do in machine shops back in the old days.....if they were the "old" days that is. [img]/forums/images/icons/crazy.gif[/img] You just needed a file that qualified as very old and worn out, but the problem often was that the shop foreman might not quite agree with you on the condition of the file. [img]/forums/images/icons/crazy.gif[/img] They make some great looking sparks when you grind them down. [img]/forums/images/icons/smile.gif[/img]

[eccentricfarmer]

Made a few this way and learned a lot and had even more fun. Some of the best knives i have, made myself.

Had to reread the post. I used a bench mounted grinder. Have to go slow with it or risk getting them too hot. Belt sander for some of the finish work.

[DarelS]

You fellers may already know this, but it's MUCH easier to grind a file down if you anneal it first, then re-temper after grinding. To anneal, heat with a torch or forge to the point that a magnet won't stick to it, then put in a bucket of wood ashes or vermiculite and leave until it cools completely. This takes the factory temper out, and makes it much softer and easier to work. After grinding to the shape you want, you need to heat treat and temper, or it will be too soft to hold an edge. There are LOTS of different heat treating methods (google "heat-treating knives"), but the quick and easy way is to heat to red-hot and plunge into a bucket of used oil (keep the lid handy in case of flare-ups, though I've never had one). Do this a couple of times. This makes the blade very hard, but too brittle; it'll break. Then heat it in an oven to about 350 for 1 to 2 hours, and air-cool (if you don't want to use an oven, use the torch until the steel is a straw color, but it's harder to maintain an even temp this way). Do this a couple of times. If it's a good sized blade, after it's cooled you can heat the back or spine to a dark blue color with a torch, that will make it flexible enough to avoid breaking without taking the hardness from the edge. If you're going to use rivets or screws for the handle, heat the tang to blue also, that will make it easy to drill the holes (same if you're going to thread the end of the tang for a screw-on cap). It's a toss-up, it's more work overall, but the shaping is much easier. Heavy grinding work on hardened steel can build up enough heat to take the temper out anyway, so I think it's easier overall to anneal, grind, and then re-temper. NOTE to real bladesmiths - I know this is very simplified, and there are lots of different ways (and theories) of heat-treating. This will get the job done pretty easily for casual knife-making.