Knife From a Rasp





Introduction: Knife From a Rasp

In this build I will show you how I made a knife from an old farriers rasp to sell to a friend.

I will try to explain my methods as easy the understand as possible so forgive me if I fail.

Step 1: Design Your Knife

when making a knife for someone else you should ask if they have any design input. My friend just told me to surprise him so this is what I came up with, if you need inspiration Pinterest has some great pictures of knives. I try to keep my handles at about 4in but that's just me, the blade I put at about 5 1/2in

Step 2: Find Material

Now this step is important. To get a knife to keep it's edge you need to harden the metal, normally when making a knife you use a softened piece of metal, grind it to the shape you want and then heat treat it which makes it very hard and then use a prosess called tempering to make the blade less brittle. Using a file gives you an advantage if you do it correctly, because a file is already heat treated all you need to do is temper it and then grind it to shape. But you must be very careful not to burn the metal, if you do then you'll have to heat treat it to regain the hardness, so when making this knife whenever it gets to hot to hold cool it in water.

the farriers rasp or file you can find at garage sales or flea markets

Your going to need to heat up the metal to 400'F and keep it at that temperature for 2 hours. You can use whatever you have to do this, I used our families oven the first time but (see story below) after that incident I've had to use the barbecue, but I'm not sure how well it keeps a steady temperature, so I would say the best thing is what my cousin uses which is a toaster oven which he bought at a garage sale

You'll want to clean it off first. I tempered a large batch of files at once in our oven which included 3 farriers rasps which are used to file horse hooves and I smoked up the house

Now useing an angle grinder I ground the teeth and filings down to get a smooth surface

Step 3: Cut Off Excess

put the design that you have on the rasp, mark then cut the excess off the rasp and profile the blade with the grinder

Step 4: Finish Profile the Blade

I use a 4x36in belt sander to profile the knife.

I follow the lines mostly but now you can go pretty much by feel

Make sure to keep it cool

Step 5: Bevel the Knife

I use the sander to bevel the blade,

there are ways to do this using measurements but I like to do it freehand.

Hold the blade at the desired angle to put the edge on it, and repeat on the opposite side. keep the sides as even as possible and keep the edge straight

Step 6: Soften Handle

now from what I told you before you know you want the blade hard, but your going to want to drill holes for the handles so we have to soften the handle without softening the blade

To do this place the blade in a fireproof container fill it with enough water to cover the blade. Use a torch to heat up the handle until the colour turns bluish. Let it air cool and now it will be soft

Step 7: Drill Holes

You can use a hand drill but it is very difficult to keep the holes straight that way. My cousin has a drillpress so I use that measure the holes trying to keep them even.

I drilled a lot of holes for looks but you don't need that many only about 2

Step 8: Clean Blade Part 1

Frequent dipping in water will make the blade rusty to clean this place the knife in an old cup full of vinegar, just don't leave it in for more then a day. I left a blade in too long once and it became pitted and was very difficult to fix

Step 9: Clean Blade Part 2

using the vinegar puts a grey hint to the knife. to clean this and to make the knife look nice clamp the knife down and hand sand I use WD 40 to aid this

Step 10: Find Handle Material and Pins

I forgot to take pictures of the wood before I cut it so I put a different picture

Find a nice looking wood for the handles I think what I used is oak

Find pin material that fits your holes, I used two different kinds for a cool look

Step 11: Cover Blade

i didn't want to get glue on the blade so i wrapped the blade in a paper towel and taped it on

Step 12: Glue Handle Scales

so I use 2 part epoxy which cures in 5 mins so these pictures are from before I glued it

Mix the epoxy spread on one side of the handle and blade push the pins through the holes spread glue on the other side of the handle and blade and push on. clamp the sides tightly and leave overnight

Step 13: Remove Clamps and Cut Pins

after the glue is dried remove clamps and use the grinder to cut off the excess from the pins

Step 14: Shape the Handle

useing the belt sander and grinder with a flap disk shape the handle

Then hand sand until smooth

Step 15: Apply Finish

I use mineral oil as a finish, but you can use a stain or other kind of oils

Rub on the handle and let dry

Step 16: Finished

Done, I then made a sheath for it but I didn't have enough time to take pictures of the process

Take some cool pictures beforehand if your going to sell it

Comments and constructive criticism is appreciated

Thanks for reading I hope you enjoyed the instructable



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    25 Discussions

    Where so you get them. I've looked and can't find anything small enough that would work..

    Very nice work! Voted!

    Nice project. Does it cut well?

    Cool build. I have a few blacksmthing secrets that might help you:

    Put some Sodium Carbonate (Washing soda) and some baking soda in your water, and it will stop the rust from sticking to the blade as much.

    Files are hardened extremely hard, so be very careful with your temper and your work, so as not to crack the brittle file.

    Also, be careful when you cut the shape, as the heat from the grinder will blue the steel and ruin the heat treatment.

    The blade looks really cool; it almost has a carbon fibre look to it. (Try some for the scales next time. That would look awesome.)


    1 year ago

    Interesting build. Was the metal hard to work with being it was a rasp? How can anyone not like a home-made knife? Bravo sir bravo.

    8 replies

    Yes it was harder to work with, but I don't have the tools to heat treat so its a trade off.

    Heat treating isn't really that hard, if you have a lot of patience you can use a blowtorch, or dig a hole in the ground with a hairdryer going into it, build a fire and it gets plenty hot. When it gets to a temperature that it is no longer magnetic, dip it in canola oil for about 8-10 seconds (usually preheated oil with another piece of steel) then let cool. After that, just temper it and it should be hardened.

    I want to try with a torch but I don't have one at the moment. I'm in high school, and still live with my parents and my dad doesn't like fire. But thanks for the ideas

    lol I'm a freshman in high school and I just finished making a new forge that I accidentally melted steel in. But I get the fact that your parents don't like fire, mine are always nervous but I always have a bucket of sand, a bucket of water, and a fire extinguisher on hand

    You melted steel!!?? That's crazy and cool. My cousin and I tried to build a forge but it didn't turn out so well, it was just losing to much heat. Good luck on future forging projects, if you want to see some super talented guys who make weapons check out Man At Arms: Reforged

    Yeah, I used a simple venturi propane burner and I upgraded it to a forced air burner with a hair dryer, and was using it in a forge like the king of random's, then I upgraded that with refractory in an old helium tank. Good luck on your projects too and I already watch Man At Arms: Reforged as well as a ton of other maker people on youtube like jimmy diresta

    Have you looked on this site for forges? There are some smaller ones that require only a hand held propane torch for heat. A large juice or coffee can as the shell and some home made refactory. Loved the way you left the files teeth marks in the knife ;-)

    Truly a very nice job.I hope to get around to doing a fine job as you did.But I only can wish. ;-)

    Really cool instructable! I do mainly forging for my blades, so I've never seen someone use stock removal (grinding) for a file/rasp knife. It gives it an interesting pattern.

    Great job!

    really like the way you left the rasp teeth showing in the spine, nice artistic touch.

    Wonderful! You did a great job. My son is going to want to try this, so thank you for being flexible and making do with what you have. I don't like buying more tools. :)

    Nice knife! But how do you grind off the teeth & filings (end of step 2) without overheating it?