In response to a recent question forwarded to me from another contributor to RYPN, I thought it might be appropriate to share the following advice regarding fastenings that use rolled threads rather than die cut threads:

You should never use a thread die to try to "clean up" a fastening with rolled threads without consulting the manufacturer. If the thread looks to be damaged the fastening should usually be replaced with a new fastening built to the correct and applicable specification.

Rolled threads are used on on certain highly stressed applications in machinery. The rolling process puts the metal under the thread area in compression, to try to avoid the development and propagation of cracks in the bolt or stud. Use of a thread die on rolled threads can result in cuts and rough spots in the thread, particularly at the critical intersection between the end of the threads and the shank of the bolt or stud. This can result in failure in operation with resultant damage to machinery and risk to personnel.

PC

This would explain why I have observed rolled threads on some new old stock flannery type (don't know if they are "name brand") flexible staybolts.


Jason

There was a Flannery Bolt Company of Bridgeville, Pa which made flexible stays and an electrical tester for them. (Page 299 in the '41 Cyc). Googling around I found a photo on Flicker from someone who said his dad was an exec with Flannery and that they went out of business around 1958.

Steve

Actually, one shouldn't use a threading die to clean up cut threads either, although I know most people do just that, and so have I. But they do make tools called thread chasers that are just for this purpose, which should work as well on rolled (also called formed) threads as well as cut threads.
Not to be confused with the same term used for chasers in die heads.
Rolled threads are preferable just about any time they can be used for the reasons mentioned by the OP.
Interestingly though, when making fasteners thread forming is also faster and easier than cutting, thus is also less costly. One instance where you get better quality for less cost.
Mark D.