I made one a while ago from 7/8" stainless tube, the first piece went wrong as i didn't allow for the tube to spring open slightly, what i did was to weld flat plates on the end of the tube to clamp to the milling table, i then milled a 3/8" slot a couple of inches shy of each end and then cut the ends 45 degrees, To get it right i milled a 5/16" slot and when cut it sprung out to 3/8"