Polishing and surface finish for forge service

Working Ra targets by die type, why mirror finish on a hot forge cavity is wasted effort and sometimes harmful, and how to pick stoning, diamond paste, or abrasive flow machining for the job.

6 min readLesson 9 of 13

Knowledge check

A polisher returns a hot-forge aluminum die quoted at SPI A-1 mirror finish, Ra under 0.1 µm across the cavity. On the first run the parts gall at the deep pockets and pickup material on the cavity walls. What went wrong, and what Ra would you have specified instead?