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Leadscrew
From Wikipedia, the free encyclopedia
A leadscrew is a large screw used to actuate precise movements of the tool or the work when performing cutting or grinding operations on a machine tool. The precision of the surfaces of the parts made on the machine tool are limited by the precision in the surfaces of the machine tool's leadscrews. For this reason the threads of a leadscrew are made by an initial cutting operation, but the final surface is made by grinding. During this final grinding process the smallest depth of cut is used to minimize the forces between the leadscrew and the grinding wheel. This is done to ensure that the deflection of the screw during grinding is negligible. For this same reason the leadscrew is made to be overly robust. The thread profile of most leadscrews is 29 degree trapezoidal. The leadscrew does not mate with an ordinary nut but with a rolling element nut, like a ball bearing. This further increases precision in motion.used in cars.drive gearing.
In a lathe the leadscrew is oriented beneath the ways, and parallel to the rotation of the part.