EVALUATION OF THE EFFECT OF HIGH-SPEED MACHINING ON TAPPING

This paper summarizes tapping characteristics at speeds as high as 9,000 rpm (180 m/min surface speed) as compared to traditional tapping done at speeds from 500 to 1,500 rpm (20-30 m/min). High speed tapping was achieved by synchronizing the spindle rotation and the feed motion of a specially built machine at extremely high speeds and acceleration/deceleration rates. This investigation analyzes the performance of roll and cut tap geometries in the high speed tapping of 319 aluminum. The torque required by the different tap geometries at several speeds and percent threads combination is evaluated. The relationship between pretapped hole diameter and minor diameter of the thread and the estimation of percent thread are analyzed. The thread quality generated at high speeds is also evaluated. It is shown that the cutting speed does not affect the steady state torque and the shear strength. The torque for roll forming taps is higher than that for cut taps. The shear strength of roll forming threads increased with percent thread.