Study on the Efficiency of Lead Screws

In this paper, the method of machining and the experimental result of three types of nut thread flank for improving the lubricating property of lead screws are described, namely the nut thread flank with sloped entrance gap on the nut thread face, the nut thread flank with three dents per one pitch on the nut thread face, and the nut thread flank with hydrostatic recess. The obtained results are as follows.(1) The nut thread flank with sloped entrance gap on the nut thread face can be machined simply with excellent accuracy when the pitch is changed by exchanging the change gears of a lathe.(2) As for the nut thread flank with three dents per one pitch on the nut thread face and the nut thread flank with hydrostatic recess, the required forms can be obtained simply when a pair of eccentric gears are used in the change gear train of a lathe.(3) As for the experimental results, the minimum frictional coefficients of the nut thread flank with sloped entrance gap and the nut thread flank with three dents per one pitch on the nut thread face were O.12 and O.08, respectively. In case of the nut thread face with hydrostatic recess, the minimum frictional coefficient resulted in 0. 004, and the peculiar property to the hydrostatic lead-screw and nut assembly was shown.