Tang for interchangeable rotary machine tool - has four main flats with secondary flats at thirty degrees to bisectrix of main flats

摘要

The tang may be incorporated on drill-bits or gimlets having a cross-sectional profile which improves the liaison with a chuck. The profile includes four principal flats (2) at ninety degree intervals together with four ancillary flats (3) at thirty degrees to an axis (4) bisecting two principal flats. Ancillary flats on one side of the axis may extend over a greater axial length together with the principal flat on the opposite side. A circumferential groove may separate the long flats from the shorter flats, the shank between tool and tang being of a reduced diameter.