By: Wayne Meulendyk
ACME screw threads are used for power transmission. The common threads used for fastening use a 30° flank angle. Some engineers desired to use a 0° flank angle for power transmission. Much engineering work was invested in determining the ‘best’ thread flank angle for power transmission. It was determined that mechanically, 14.5° was the best. It was named: ACME. The word ACME means “the best”.
Other than the 29° ACME included thread angle, there are several options for ACME threads. They include: General-Form, Stub-ACME, Centralizing ACME, and Centralizing Stub ACME. To extend the confusion the Stub ACME has standard modifications: M1 and M2. To compound the selection difficulties many engineers have developed, and are still developing, their own versions of the ACME thread to meet specific design goals.
One more piece to really muddy the water is that the Tr-series has a 30° included angle, is also used for power transmission and has similar Stub and Centralizing options.
Just remember that at Gage Crib Worldwide Inc. we can assist you in determining the correct tool to measure these threads Just contact us and start a conversation. You will be glad you did.