Helical toothed broach

A finishing broach for finish cutting helical teeth of a work piece, comprising an elongated broach body having a multiplicity of series of helically aligned teeth arranged to finish cut previously formed teeth on a work piece, all of said teeth having side surfaces conforming to the profile shape of the spaces between adjacent teeth on the work piece, each tooth having side surfaces helically inclined to the longitudinal axis of the body to define obtuse and acute included angles with its front face;

• the leading section of said broach having teeth which at the acute included angle side thereof have cutting edges which are progressively stepped laterally and backed off to take sequential cuts for substantially the full height of the adjacent sides of the work piece teeth,
• the teeth of said leading section at the obtuse included angle sides thereof being neither laterally stepped nor backed off and which therefore provide guide surfaces in true helical alignment which cooperate with the adjacent side surfaces of the work piece teeth,
• the following section of said broach having teeth all of which at the obtuse included angle side thereof are laterally stepped and backed off to take sequential cuts for substantially the full height of the adjacent sides of the work piece teeth,
• the teeth of the following broach section at the acute included angle side thereof comprising in sequence a first few teeth which are not laterally stepped but in which the side surfaces are backed off,
• a single following tooth which at its acute included angle side is neither laterally stepped nor backed off, but has its side surface substantially chamfered rearwardly from its front surface,
• the remaining teeth of said following section at the acute included angle side thereof being neither laterally stepped nor backed off to provide guide surfaces in true helical alignment which cooperate with the adjacent side surfaces of the work piece teeth.