This technical report describes procedures for cold root rolling the thread roots on API 7-2 thread sizes using CNC Lathes (CW/CNC). Cold working can be applied by a couple methods: (1) cold rolling under pressure with a roller shaped like the thread form, or (2) shot peening. Both methods achieve acceptable results, but machine thread root rolling is more controllable.
It is not the intent of this technical report to explain the benefits of thread root rolling, but the manufacturing process and quality control requirements. This technical report will address the best practices (or recommended practices) to cold root roll API 7-2 threads and identification marking.
This technical report will not address cold root rolling using manual lathes (CW/Manual)—a similar process but with different tools used for the pin and box. However, the tools described in this technical report can also be used on manual lathes. The steps to position the CW roll into the thread and the paths the tools move can vary between CNC machines controls.