tapping holes

The rule of thumb is three threads in the metal.

I'd suggest PEM Nuts they press in and are threaded holes.

Mart> I need to drill and tap holes in 1 inch x1 inch sq. alum. tubing with

Thanks for reply .Are PEM nuts plastic and who would be most likely to stock them. One more question ? Have you had any experience with astralloy alum. welding rods using acet.and oxy. torch instead of bolting on a side piece thanks hlb

Pem nuts are made out of various metal - Al, SS, and such. I don't recall seeing any in plastic. They would have to be welded.

Check out

R.C. Dudek & Company, Inc was/is one. CA, WA, NC.

Check the web.

Mart> Thanks for reply .Are PEM nuts plastic and who would be most likely to