I an looking to make an adjustable head for a spotting scope and I need a recommendation for material.

I need a 3"x4"x4" or so hunk of plastic. I have seen a gray industrial material that I think wound be perfect but I don’t know what it is.

I need to ‘machine’ this on my drill press with not much more then an end mill and a cheep X,Y table

A fairly hard non slippery plastic that I can tap to say , ¼ 20 without cracking (with due care)

I think plexiglass may be too prone to cracking, nylon may be too soft Delrin would be OK but this will need to clamp to a ¾ or 1" shaft and stay put. May still be OK but I wish I knew what the gray stuff is

Thanks in advance for your help…John