Acme Thread Chart

The acme thread profile is probably the most widely used thread profile for designing lead screws for power transmission or linear motion in the United States. The European equivalent is the trapezoidal screw. The acme thread form was established over 100 hundred years ago, replacing square thread screws. There are two basic types of Acme screws: general purpose, with clearance on all diameters .

The Acme thread is the original non-metric form of the trapezoidal thread and the most commonly used type of thread in the world. Developed in the 19th century, the Acme thread is utilized for large-scale motion and power transfers on machines. In the United States, Acme screw threads are considered an improvement over V-shaped, typical square and other metric threads. Toolmakers and CNC (Computer Numerical Control) machinists observe that Acme threads are squarer, which affords easier cutting by die or single-point threading. Acme threads are stronger, wider and more durable than other threads, with better load capabilities and smoother, faster engagement of half-nuts on lathe lead screws.Acme threaded lead and rod screws fall in three major classes: stub; the more efficient centering/centralizing; and general-purpose screws. Acme short-length threads work on hose connectors, valve stems, steering mechanisms, bonnets on pressure cylinders and camera lens movements. Long-length threads help control movements on conveyors, machine tools, jacks, aircraft flaps, and testing machines.Many metalworkers report that, due to its wider shape, the Acme thread angle is not as efficient as some other threads, and it produces greater radial load on the nuts. Other machinists prefer Acme threads, insisting that, because they are wider and thicker, the threads provide optimal operation of machinery in environments where there is a lot of debris and dirt. For mechanical engineers, including CNC buyers and builders, the lead accuracy, straightness and tolerance of Acme lead screws is an important advantage.The Acme thread angle is 29 degrees with a thread height that is half of the pitch. Its valley and apex are flat. Trapezoidal metric forms are closely identical to Acme threads, except for the angle degrees, which can make a major difference in metalworking projects, requiring equipment, such as lathes, drilling machines and grinders, routers and high-powered cutting devices.Several websites post charts for Acme thread designations.