Some Experiments on Tapping

Abstract

The research was undertaken to investigate tap breakage and the production of accurate threads. Descriptions are given of the machine and the test method used. The threads tapped were inspected by taking plaster casts and profiles of the casts were projected to a × 50 magnification. These revealed serious errors in thread form, and details are given of a method devised for axial loading of the tap which resulted in the production of almost perfect threads. For precision tapping, it is recommended that the tap is held rigidly. Mention is made of the effect of swarf building up in the flutes and its influence on torque value; the effects of taper, number of flutes, and surface finish of the tap; the speed of tapping and lubrication. Taps of diameters , and -inch B.S.F. and B.S.W., having three and four flutes and a wide range of different metals, were used.