3/4 inch UTA ball truss clamps

To make 1 clamp you will need the following hardware:

McMaster-Carr specifications:

(1) 94459A220 M5 Heat-Set Inserts for Plastic

(1) 91595A139 Dowel Pin

(6) 91290A270 60mm bolts

(2) ¾" threaded balls

(1) 1692K52 conical spring

(1) 91287A333 M5 Hex bolt for the knob

McMaster-Carr has all the dimensions for the parts that you can shop elsewhere affordable. 

See exploded view for assembly.