Start with a Harbor Freight Chain Breaker.

Take it all apart and get your drill press out.

Drill out the parts shown:



Toss the bits that have the X next to them into your junk drawer.

Put it back together as a cotter press. Don't forget to grease the threads:


You will have 2 pushers that go in from the inner side. One is a spare in case the thin part breaks. I doubt it. It's got to be stronger than the cotter threaded part and because of the way it is built should not twist inside the tool.

Place tool over cotter/crank and tighten outer bolt until the pusher touches down:




Press out cotter using inner bolt: