Development of Cutting Method for Round Metal Tube Using Torsion

Abstract

To improve material yield, roundness and cutting speed in the cutting of round metal tubes, a new cutting method with torsion is proposed. First, narrow grooves are made partially in the circumferential direction on the outer surface of a tube. One end of the tube is fixed and the other end is rotated. By adding torsion to the tube, a crack occurs restrictively in the narrow grooves and the crack propagates along the circumference. In conventional tube press shearing, the need to insert of precise inner cores into the tube with accurate positioning is time-consuming. Thus, in the proposed cutting method, the edges of a tube are grasped by three soft jaws attached to a power chuck of a lathe without inner cores. Even if inner cores are used to increase the holding force of the jaws, the accuracy of the diameter and positioning of inner cores is not necessary to insert them into the tube smoothly. In this report, the shape of the soft jaws and minimum chucking length were examined. Cutting trials of A6063TD and STKM11A tubes were carried out and it was confirmed that the tubes can be cut so that burrs, shear droop, and the deterioration of tube roundness do not occur.