Lead screws are produced in both inch and metric sizes. The inch standard is a modified ACME thread style and the metric standard is a modified Trapezoidal style. The thread forms are very similar between the two and there is no significant advantage in performance of one over the other. The choice of an inch or metric product generally comes down to two issues: what is the most ideal lead (travel per revolution) for tmy application and what units are native to the equipment I’m designing? In many cases, the selection of inch or metric depends simply on lead availability. Once the lead constant is entered in the control system, there is little difference whether the screw is inch or metric.