Thanks Carol - you were only off by 50% (or 100%, depending on how you look at it ). As it turns out, the HF clerk I talked to suggested the same idea of cutting the head off of a bolt. I didn't have enough experience with bolt threading standards, so it was hard for me to believe that anyone would use 11 threads per inch for anything but a custom (angle-grinder-only?) application.
But sure enough! [THIS TABLE] declares it to be the standard (coarse) thread for 5/8" bolts. Learn somethin' every day!
I had to run an errand right after I saw your answer. While I was gone I thought about how I could prevent a bolt from bottoming out in the HF sanding pad. I came up with the same answer as ...
... Tony! Thanks for your response. I have a question ... suppose I did the following:
1) Cut the head off a 5/8" boltAt this point, could I not use a file to reliably turn the shaft down to the size needed for my hand drill? I guess the problem would be getting the shaft to a consistent diameter, eh?
2) Mount the threaded part of the bolt shaft into a scroll chuck on my woodturning lathe
3) Mount a drill bit in a Jacobs chuck in the tailstock and (hopefully) make a
"clean" divot in the center of the smooth end of the bolt
4) Replace the drill bit in the tailstock with my regular live center, and crank it firmly into the end of the bolt
Hmmm ... is it possible that there's a commercially available solution out there? I haven't done much searching yet; I'll keep looking.