BSW thread ring gauge british standard whitworth thread
Part No: RG-310
Standard: BS84.1956
The British standard coarse screw thread is known as a parallel screw thread of Whitworth form having a 55 degree included angle. With the standardization of Unified threads, the BSW Whitworth thread form is typically being utilized for replacement parts. Steel bolts of ¾ inch and below should not be made to close class limits and instead should be specified to medium class.