Make a Quick Knife From a Clutch Finger




About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific...

A dozen spring steel fingers encircle the pressure plate of an automotive clutch.
Here's how to make a nice knife from one of those spring steel fingers in a few minutes.
It's got a nice long handle so I can use it as a Crooked Knife.


What you'll need:
A junk pressure plate from a clutch.
A chunk of stainless steel tubing an inch or less in diameter.
A vise
An angle grinder and some abrasive cutoff wheels.
A belt sander
Safety goggles

Step 1: Cut Apart the Pressure Plate

I'm using an abrasive cutoff wheel to cut off the rivet heads that hold the assembly together. Every pressure plate is made differently. Be careful. There may be some spring-loaded parts that can jump at you or bind your tool.

The abrasive wheel is dangerous enough by itself. It may fling metal shards into your eye. It may break and fling fragments at you. How do I know that?...

Step 2: Dangerous?

So there I was, happily grinding away and "BANG!" PAIN IN MY BELLY.
I didn't want to look. Scared to death I gimped into the next room yelling "check me!". I thought I'd be bleeding and maybe disemboweled.
Here's what it looks like.
The grinding wheel had broken and threw a piece that hit me in the gut.
Another piece hit the wall, making a sound like a gun.
If I'd been hit in the face or the eye, I hate to think what would have happened.
The piece that hit me did this damage through two vests, a shirt, the top of my pants, and belt.
I guess that's why they want you to leave the guards on the tool and wear a grinding mask.

This particular grinder is a very dangerous one.
There's no guard, and it's so old it never had one. There's no speed regulation, so it can spin at excessively high rpms when there's no load.

I'm so glad it didn't hit me in the eye because I've seen THE WORST PICTURE IN THE WORLD,
which is the next step.. Skip it unless you want to see a horrible photo and read some ranting that won't help you learn to make knives.

Step 3: I Mean It! Broken Grinding Disc Vs. Eye


So while I waited for the pain to die down enough to continue working, I did a search to see if the tool was as dangerous as I thought it was. According to the New South Wales Institute of Trauma and Injury Management it is. And they took this photo to prove it. He lost the eye.

This photo reminds me how much I'll regret building ANYTHING EVER if I have a serious accident or if any of you have one.

This is the sort of injury fragmentation munitions are designed to produce. Remember that the next time we decide to invade some random country. Or if someone offers you a job doing that. They'll probably tell you the job is "defending your country". I have a better plan. Let's send 200,000 teachers to some country that's messed up. I bet their casualty rate will be extremely low. I doubt they'll destroy towns or kill each other in "friendly fire" accidents.

Okay, that's it for ranting today, let's get back to making that cool knife.

Step 4: Cut Off Some Fingers

Cut them off the pressure plate that is.
If the metal changes color, pour some water on it to cool it or quench it with a wet sponge.
If you overheat the steel it will soften the temper.

I've got to get rid of that grinder. There's no bracket to attach a guard. If you ever have to use a tool like this, keep the parts of your body you care about out of the plane of the spinning disk.

Step 5: Stainless Pipe Handle

Cut a chunk of stainless tubing and squish it in a vice as shown.
It doesn't have to be stainless, suit yourself. I like a long handle less than an inch in diameter.

Step 6: Grind the Tang

The tang is the part of the blade that fits into the handle. It needs to be a little bit oversized. I left shoulders to seat against the edge of the tubing.
I used a belt sander to grind mine down.

Step 7: Keep It Cool

I poured water on the belt so it wouldn't heat the blade as much. It still heated it, so I kept dipping it in water to keep it from overheating.

Step 8: Assemble!

You can see the finished shape of the tang, including square shoulders with the blade.
I used the vice to squish the tube as much as I was comfortable with. I left the tang a little oversized.
I pounded it into the tube with a hammer.

I took it out of the vise and tapped it on the table. It makes a really nice ringing sound.
Very solid and tight.

Step 9: Deburr the Handle

The handle had a burr where I'd cut the pipe to length with a hacksaw. I used a flat file to deburr the outside. I used a rat-tail file to deburr the inside of the pipe.

Step 10: Blade Shaping

Back to the belt sander. First I shaped the outline of the blade, then I ground the bevels on the blade and rough sharpened it. I kept the blade wet and kept dipping the blade in water. I didn't overheat and discolor the blade at all.

Step 11: Sharpen

I sharpened the blade on a diamond stone. Want more details about knife sharpening?

Step 12: Sheath

I cut a chunk of bamboo to use for a sheath. You could also wrap the blade with paper and tape to make a hasty sheath, or use a chunk of plastic tubing squished in a vise.

Participated in the
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    126 Discussions


    4 years ago on Introduction

    Whoooaaaaa all I could think was "fffffff that must have hurt" When I saw that picture. I saw a guy chop his finger clean off once. Sad because he never got it back on either a good reminder to everyone. Thanks for this write up. Do you know what kind of steel those fingers are made from?

    black hole

    6 years ago on Introduction

    I bet you could make a lot of push knives using this method.


    7 years ago on Step 4

    after completing a two week OSHA course i learned that harmonics is one of the answers, if you tap your grinding wheel with a screwdriver and listen for a clear ringing sound you can tell if the wheel has cracks or defects. Guards were invented for a reason though and retro fitting one or getting rid of tool is best bet.


    7 years ago on Introduction

    Best warning ever , and you have to click to see it , and please tell me you have replaced the grinder for e better one .
    btw I'm glad you're ok :D


    7 years ago on Step 3

    200,000 teachers to an enemy country where the 500,000 pupils ( OH, GOOD PUN ) are armed with ak-47s ??


    7 years ago on Step 3

    i cannot unsee what has been seen...

    Why didn't you just use a torch? It would have been so much easier, faster, and much more safe.


    8 years ago on Introduction

    Because war didn't make us everything we are today...



    8 years ago on Introduction

    My neighbor and I made something similar once only instead of making the blade we welded the blade from a broken pocket knife on. The pic of the eye is extremely gross but if that won't convince someone to take proper safety precautions nothing will.


    8 years ago on Introduction

    My grinder also expoded a cheap grinding wheel once, hit me in about the same place too!...mine did have the guard on, the piece went around the guard...


    8 years ago on Introduction

    Nice knife...

    *puts guard back on grinder*


    10 years ago on Step 3

    Congratulations on throwing politics into an otherwise good instructable.... Semper Fi...

    1 reply

    Reply 8 years ago on Step 3

    I agree, this is instructables, NO POLITICS PLEASE FOLKS. You all know we'll never agree.

    Damage, Inc.jakebuck

    Reply 10 years ago on Introduction

    Wrong? How is that "wrong"? All my life I'd been told smoking was bad, but the point didn't hit home until I went to the exhibit at the museum of natural science that showed what a smoker's lung looked like next to a normal lung. A picture is worth a thousand words. The picture is an adequate warning to people, and it pertains to the instructable. It shows what can happen to someone if they don't follow safety procedures. Yes, it is a shocking picture. It's SUPPOSED to be.

    jakebuckDamage, Inc.

    Reply 10 years ago on Introduction

    Its wrong for multiple reasons. There was an inadequate warning. This site is generally family-friendly. If the pic was on anyone else's instructable, it would have been removed. Enough said.

    Damage, Inc.jakebuck

    Reply 10 years ago on Introduction

    The warning was adequate. It is mentioned once in the first step, again in the second step, and also in the third step. To see the Full picture, you have to click on it. That's 4 warnings. GENERALLY family friendly. That doesn't mean ALWAYS. Also, this is an instructable about making a knife from parts from a car. I doubt that anyone very young will be viewing this. If it were on anyone else's instructable, it would've been removed? I doubt that. I think you're just assuming this. Have there been past examples of things like this being removed?