Introduction: 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 I…

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.

Epilog Challenge

Participated in the
Epilog Challenge