This is my simple yet very useful bending jig / platen & pins for use with an anvil hardy hole. The platen is made from a 19mm (~3/4") thick plate and is 100mm (~4") square. The pins (six included as shown) are made from 1045 medium carbon steel and are milled to fit the nine 19mm holes and four 13mm holes. The holes are slightly oversized to account for expansion / distortion of the pins under heat.
It can be made to fit hardy sizes 3/4" up to 1&1/4" (19mm to 32mm). You can specify your hardy size in either fractional inches or millimeters.