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

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

Drill
Grinder
Sandpaper
Wire cutters
Gas Torch

Step 1: Cut the Screwdriver

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.

Step 2: Grind the Punch Into Shape

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.

Step 3: Harden the Punch

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.

Step 4: Clean Up

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.

Step 5: Temper the Punch

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.