pic: Ultimate chain tool project

[aldaeron]

I would consider the next step up for re-usable fasteners - a keyed insert. The brand name I know is Keensert. These are much more robust inserts, but do require some specialty tooling. I would see if a local machine shop would lend the tooling to you. This was our standard insert for aluminum vibration tooling to allow easy install of control accelerometers. We found that using tanged or tangless helicoils over and over again was a bad idea and once we switched to Keenserts the problem went away.

-matto-

[topgun]

A couple of points:
1) Why not machine it out of 1018 steel? Tormach can handle steel.
2) Why do you want to push the pin out? I made one for my team and it's set to push the pin out enough so you can break the chain while leaving the pin in. Then you have a pin ready to push right back in. This is much more secure than any connecting link you would use.
3) I used an injector pin for the part that is actually pushing against the chain pin. These are very hard and won't mushroom out, plus you can get them sized to fit thru the pin hole.
4) Make sure you have enough leverage available on the handle to actually move the pin. We used a shcs so we can put a long allen wrench in it or even use a drill with a hex bit.

[MechEng83]

Some additional comments I didn't see written:

I'd recommend you use fine thread rather than coarse thread. The screw will be easier to turn.

Are you machining the all thread down to the point? If I understood your description, it's case hardened, but that won't help you if you machine away the case. For our custom #35 chain tool (and the replacement we used for the #25 that broke) we used a hardened dowel pin inserted into the end of the screw.