Spring Punch

by mikeandmertle in Workshop > Tools

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Spring Punch

Spring Centre Punch.png
Spring Punch

I lost my automatic centre punch a few months ago and while I was looking online for a new one I came across one that was just a centre punch with a spring. It was a cool design I'd never seen before, but I ended up buying one like I had lost. I came across some old springs at a thrift store recently and had an idea last night that I could try and make one of the sprung punches, so I went back and bought the springs in my lunch break and after work quickly made this centre punch.

It works well and was surprisingly quick and easy to make.

Supplies

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  • Long Extension Spring
  • Old Screwdriver, needs to be larger diameter than the spring


  • Drill
  • Grinder
  • Sandpaper
  • Wire cutters
  • Gas Torch

Cut the Screwdriver

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The screwdriver is hardened steel so you can't cut it with a hacksaw, you will need to cut it with an angle grinder with a cut-off disc.

Cut the screwdriver head off and then measure off about 50mm of the screwdriver and cut it off.

Grind the Punch Into Shape

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I used my old trick of sticking the piece of screwdriver shaft into an electric drill and spinning it against the grinder. The goal of this first grind is to create a step that the spring can fit over firmly, but has a hard edge so the spring wont migrate onto the punch section.

Now flip the shaft around in the drill and grind a taper onto it, finally grind a steeper angle onto the point of the punch. I did the final point by hand without the drill.

Harden the Punch

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The screwdriver shaft was already hardened, but unless you are very careful to not overheat it during the grind you'll probably remove the hardening.

I heated the punch up to cheery red and checked that it no longer stuck to a magnet, then gave it another burst of the torch and quenched it in cooking oil.

Clean Up

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I put the punch into the drill and held some sandpaper against it to remove the burnt oil. Lastly, I gave it a quick buff to bring out the shine.

Temper the Punch

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You need to temper the punch so it doesn't just break when you use it. I wanted this a little harder than a knife blade so I only put it in the oven for 45 minutes at about 180°C and then let it cool.

The Spring

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Cut off a length of the extension spring about 100mm to 120mm long. Because the spring was a little dirty and gave it a quick clean on the wirewheel.

Assemble the Punch

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Now push the spring onto the punch head and test it out. It works well, and I'm pretty impressed with how easy this was.