These are the short, inverted flare plugs I made using that "broach".
I used a piece of 3/8-24 threaded rod. I faced the parts off in the lathe, drilled a 3/16th's dia. hole about 3/1th's deep and then used a 90 degree C'sink to make the chamfer.
This is the fitting spinning in the lathe.
I then turned it around in the chuck and drilled a .173 dia hole about .25" deep. This is the hole to be "broached". In the pic you can see the starting chamfer I put in with a center drill to guide the broach and help get it started.
A couple of taps from a hammer set it enough I could get it clamped in the vise.
After pressing it home It took a bit of wiggling to get it out of the brass but doing that didn't seem to hurt the fit or operation of the "new" driver.
Continued in next post.