in process of designing a new fabrication bench i decided i wanted to be able to use all my various clamps ive aquired/built over years.
only prob was they used mounting studs from m14 down to m6 about 80% being m12, so thats size ill be tapping holes in bench
so came up with solution below which is prototype to make sure idea worked.
had a damaged machine shaft in scrap pile which was 16mm od, turned 1 end down to 12mm x 50mm long, left 20mm sect 16mm then turned final bit to 8mm x 150mm.
then threaded short end m12 and other end m8.
tried it in scrap metal plate that i tapped m12 hole in to try it, and can clamp down really tight with no probs.
now need to make whole range in dif lengths/threads.