Sources and scope for this page: Industry convention — no single governing standard (conventional usage, definitions vary between sources), covering the definition of acme thread. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
ACME threads are designed to move loads, not to clamp parts. The 29° included angle is shallower than a 60° fastening thread, which puts more material at the root and lets the thread carry heavy axial thrust — the reason it appears on lead screws, vises and valve stems.
The flat crest also wears better than a sharp V under repeated motion, and the thread can be split with an anti-backlash nut. A 60° thread used as a lead screw wears rapidly and loses accuracy.
Common misuse
Using a standard 60° thread as a lead screw. It will work briefly and then wear out of tolerance.