G clamp that uses a 5/16" bolt. This G clamp is quite strong. I printed in pla at .2mm at 100% infill and used a hot glue gun to glue the handle and the shoe.
You could easily 3D print the bolt if you wanted to.
Jaw opens to 42mm
Revised:- 2 parts weren't sitting on bed properly and has been fixed. also added a gripper strip at top of jaw. Also have put a hole in the handle to use an extra nut which secures handle much better