What are ACME screws and Trapezoidal Screws?

Lead screw refers only to a powered screw that relies on the sliding motion between the nut and the screw shaft.There are two variations of the lead screw:the screw with square thread and trapezoidal thread.

The lead screw can have square or trapezoidal threads.

Lead screw designs for power transmission use almost exclusively trapezoidal threads,which are easier to manufacture and have higher load capacity than screws with square threads.However,trapezoidal threads do have higher friction and are therefore less efficient than the square thread form.

ALM high efficiency lead screws

As mentioned above,the lead screw for power transmission uses the trapezoidal thread form.But the trapezoidal threaded design can have a thread angle of either 29° or 30°,which means that the trapezoidal lead screw comes in two versions.

●ACME Screws

The first version(called the Acme screw)has a thread angle of 29° and is manufactured in inch size.Acme screw size is usually specified by the screw shaft diameter and the number of threads per inch or TPI.

Trapezoidal screw form with thread angle of 29°is called Acme screw,while trapezoidal screw form with thread angle of 30°is called trapezoidal screw.

●Trapezoidal Screws

Trapezoidal screws are also lead screws that use the trapezoidal thread form,but the trapezoidal screw thread angle is 30° and manufactured in metric size.The size of the trapezoidal screw is specified by the shaft diameter of the screw and the pitch of the screw thread.

Acme screws and trapezoidal screws both use a trapezoidal thread form,but they have different thread angles.

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