Lathe screw tap fixture

The invention relates to a lathe screw tap fixture. The fixture comprises an outer support shell, an inner slide block embedded in the outer support shell, a double-head cone rod embedded in the inner slide block, and a screw tap chuck fixedly connected with the double-head cone rod, wherein the inner slide block slides in the outer support shell to drive the double-head cone rod to move in the front-back direction; and the tapping depth of the screw tap chuck is controlled. Compared with a prior art, the lathe screw tap fixture has such advantages as precise control of the tapping depth.