When at first you don't succeed - Kurt vise-broken tap

[Flyinfool]

The hardening of Allen head screws is not always for bolt strength. If you anneal the head you have a good chance of stripping the hex socket when tightening or loosening. Reguardless of bolt strength thte head is usually hard to support the driver forces.

 

[Janderso]

Done and done.

 

[metric_taper]

Done and done.

So what sort of fixture attaches to the 4 other flat head screw locations on your back jaw mount?

 

[Janderso]

Here are a couple examples.
You have a built in stop also for repeatability