This article shows a way to forge a simple quadrangular handle for the Cheiroballistra. This type of handle is not pulled with hands - it is only used to lock the slider into a simple locking pin. The look of the handle is fairly close to the diagrams in various versions of hte Cheiroballistra manuscript.
I have attempted to bend a quadrangular handle earlier by cold-bending, but the results of the attempt were not particularly good. Hot-forging works much better and allows making the handle from thicker steel, which is particularly important in a quadrangular handle where a long, flat edge contacts the pin and risk for bending is thus considerably larger than in a round handle.
The process Edit
Forge a long piece, narrow piece of 5-6mm thick steel around a rectangular metal rod:
Cut off the resulting square:
Weld the seam shut.
Forge the end of the long piece of steel slightly concave. Then grind matching grooves to both the shaft and the square. This makes welding easier and increases the seam's strength:
Weld the two together. Finally drill a hole for the axle at the end of the long part.
The end result looks like this when assembled: