I took the fastener off of the Clausing 8540 over arm and it is
actually a nut and not a bolt. It looks to be either a 1/2-13 or 5/8-11
thread and the top of the nut looks like a SHCS. However, the internal
pattern looks exactly like the inside of a 12 point socket. I have no
idea what this nut is called or where to find the appropriate bit or
key to remove it properly. Any suggestions would be greatly
appreciated. Thanks, Steve