Bolt made from upsetting vs machining

[jts20]

Working on a bolt compliant to MIL-S-1222, which requires wedge testing, which is more of a test of ductility than a confirmation of strength. We have a supplier that can make the bolt by either method, and the material (4340) coming in from the mill is produced with a reduction ratio of 15:1. Will anything be be gained by forging the head of these bolts vs. just machining from the bar?

 

[SwinnyGG]

Yes.

Machining will leave machining marks (however small) which will serve as stress risers. Forging will not (assuming good quality dies and execution) and will also create grain the direction of the shank, which is what you want.