Step 1: Cutting a Concrete Nail

Concrete nail - It's harder then other nails and it will not bend.

Take a metal machine saw and cut the nail to the length of the hole of chainbreaker.

Measure thickness of the pin before and abrade the nail with metal saw to the same thickness.

*Be careful when doing this step. Hold a nail with some clamps, it can easily fall or jump from clamps and hurt you.

Step 2: Trying Out the Nail.

Try to put cutted nail into a hole of the chainbreaker arm. If it doesn't fit abrade it more with a hacksaw.

Put a bike chain hole on a nail and see if the nail comes through.

I hope you did this right and your chainbreaker works again. Good luck on your next bike fixings!