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What steel would a good quality rasp or file be made out of?

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  • What steel would a good quality rasp or file be made out of?

    Click image for larger version  Name:	image_6068.jpg Views:	5 Size:	1.48 MB ID:	1841413

    I took a hoof rasp and ground it to use as a blade on a leather splitter I am building. The blade in the photo was my first grind. It was just a straight bevel. I tried a convex and a hollow grind. The hollow grind seemed to work the best. What ever steel these rasps are made out of must be good quality because I could shave the hair on my arm with the blade.
    Last edited by Black Forest; 12-03-2019, 05:28 AM.
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    I took a hoof rasp and ground it to use as a blade on a leather splitter I am building. The blade in the photo was my first grind. It was just a straight bevel. I tried a convex and a hollow grind. The hollow grind seemed to work the best. What ever steel these rasps are made out of must be good quality because I could shave the hair on my arm with the blade.
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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    • #3
      I don’t know the actual spec but they are generally made from plain high carbon steel around 1% carbon, a chap local to me makes a lot of knives from them leaving part of the “cut” pattern on the blade, looks quite effective.
      John
      Knowledge withheld is knowledge lost

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      • #4
        The exact alloy is a bit of a mystery, but redgrouse listed the general specs. Plain carbon steel, .75-.9% carbon content, something close to a 1095 or W2 steel is typical.

        Word to the wise though, some guys claim that modern files are made from medium- to low-carbon steels that are case hardened only for the depth of the teeth, and are therefore useless for making a knife from. Ive never met one of those files though, personally i think the idea is bunk

        EDIT
        To be clear, i think the idea that the file being made of crap steel is bunk, a shallow hardening depth of whatever it is makes sense

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        • #5
          I had a Nicholson Engineer tell me years ago that they didn't reveal the exact alloy but if I treated it exactly like W1 I'd be fine. From the same conversation, their files are case hardened. While in the common vernacular people think case hardening means a soak, it can also mean any other process where only the outside is hardened, i.e. a quick heat and quench of the outside such as can be done with induction heating, so only the outside is fully hardened. That's what they wanted so as to have hard teeth and a more ductile core
          Last edited by Mcgyver; 12-03-2019, 11:28 AM.
          .

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          • #6
            I certainly don't claim to know anything at all about the economics of it, but my guess would be that, when done on a commercial production basis such as file makers like Nicholson, et al, it would be just as economical to choose the proper quality steel at the outset as to go through the case hardening process with a lesser quality.

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            • #7
              I have made many knives from rasps and files. I use stock removal process after tempering in a forge and then heat and quench followed by a lower temperature temper.
              The patterns can be very attractive.
              I have never found a crap steel file.
              Seastar
              I cut it off twice and it's still too short!

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              • #8
                Mind you it's been years since I've snapped a file in half, but my experience is that files are through hardened, excepting of course the tang.

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                • #9
                  Originally posted by lynnl View Post
                  I certainly don't claim to know anything at all about the economics of it, but my guess would be that, when done on a commercial production basis such as file makers like Nicholson, et al, it would be just as economical to choose the proper quality steel at the outset as to go through the case hardening process with a lesser quality.
                  Carburized file would be probably more expensive to make. 1095 type steel won't cost much if you buy in bulk. 1095 steel is probably something like 80 cents per kg and one medium-sized file weights 250g or so. Material cost for one medium size file is about 20 cents.
                  Whereas carburizing is relatively slow process and unneeded complication unless you need to make hammer-file-spudger combination tool.
                  Last edited by MattiJ; 12-03-2019, 10:50 AM.

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                  • #10
                    I think these files are case hardened. After I get through the actual teeth an into the base metal they seem easier to grind. Still pretty tough to grind. Also when I bored a hole in them with a carbide center cutting endmill once I cleared the teeth it seemed to go through much easier.

                    So now a question. For best edge retention after grinding what should I do as far as heat treating? Mind you I know nothing about heat treating but I do have access to a forge!
                    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                    • #11
                      Originally posted by Black Forest View Post
                      I think these files are case hardened. After I get through the actual teeth an into the base metal they seem easier to grind. Still pretty tough to grind. Also when I bored a hole in them with a carbide center cutting endmill once I cleared the teeth it seemed to go through much easier.

                      So now a question. For best edge retention after grinding what should I do as far as heat treating? Mind you I know nothing about heat treating but I do have access to a forge!
                      I've done some work like that in making my own chisels and punches. I would quench in brine from a dull red, and draw the temper to a straw color on the cutting edge. It may be easier to control the temper by using an ordinary baking oven at ~200C. for an hour. (ask your wife first).

                      My favorite technique however, is to do a differential temper: this makes the cutting edge hard and the rest a bit softer, like a spring temper. Harden, quench and polish your piece first. The technique is to heat up a piece of steel plate to a bright orange and set the back of your blade on it, and watch the tempering colors run up to the edge. When the straw color reaches the edge, quench it again and you are done. I have done tools in this way, which have a blue on the butt end and straw on the edge, it works well. They have never needed sharpening after that.
                      Last edited by nickel-city-fab; 12-03-2019, 12:50 PM. Reason: clarity, completeness

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                      • #12
                        Originally posted by Black Forest View Post
                        I think these files are case hardened. After I get through the actual teeth an into the base metal they seem easier to grind. Still pretty tough to grind. Also when I bored a hole in them with a carbide center cutting endmill once I cleared the teeth it seemed to go through much easier.

                        So now a question. For best edge retention after grinding what should I do as far as heat treating? Mind you I know nothing about heat treating but I do have access to a forge!
                        You might want to check the center hardness with another file.Might be still hard enough even if the teeth are harder. (Some files are also hard chromed for extra hardness and rust proofing.)

                        If you keep the file cool during grinding you don't need to do much at all for it. If it doesn't chip you can use it as-is and if it seems brittle and too hard (cutting edge chipping too easily) you can temper it in baking oven at 200C
                        Last edited by MattiJ; 12-03-2019, 01:00 PM.

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                        • #13
                          Here is a real quick video of me splitting a two inch wide strap of 14oz. leather. The blade I used in the video is a convex grind. It went through quite easily.
                          https://youtu.be/OBfppaWOCJY
                          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                          • #14
                            Dad got a Nickelson lathe file caught in the lathe and it snapped right in two. Grain pattern looked awfully like through hardened to me. Not quiet as small of grains as an endmill (didn't have that smooth dull finish) but pretty close.
                            21" Royersford Excelsior CamelBack Drillpress Restoration

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