Rich,

I usually use one thread diameter or 1/2 the head diameter if that's a
consideration
for a minimal spacing, but you can fudge that a little.

The head diameter is potentially a problem, unless I turn them. I am
not sure how to do that. How about tapping a dowel, using a jam nut to
limit depth, stick that in a collet in my mill and hold a tool bit in
the vise??

Among the other suggestions, it sounds like I can get closer to the edge
than I have planned, or go with Anthony's dowel idea.

I had not heard of thread-forming taps. They do not look cheap, but it
sounds like a great idea.



RichD, in DRY Atlanta (Spit in this direction. Anything will help)

Same here (central FL). It's pretty bad when Floridians gather by
windows to watch what rain happens to fall

Thanks for all for the replies!

Bill