Dan:
Please accept our sincere thanks for the sacrifices you and your family are making on our behalf. The older I get the more I appreciate the price you brave folk are paying and the value of your work.
To answer your question, I know of no tool for shaping the underside of a screw head to mate with the countersink. That kind of thing is typically done on a lathe with a single point tool. Lacking a lathe it could be done in a drill press by putting the screw in the chuck and using a file to shape the head.
As for engraving, the secret to that is simple. You have to take your shoes off. Ain't no one can engrave without bare feet. You put a pair of shoes on Mr. Hurst and he becomes all thumbs.
Best regards,
Glenn
