The method ofcutting teeth on a cylindrical gear by the hobbing process has been in existence since the late
1 800’s. Advances have been made over the years in both the machines and the cutting tools used in the
process. This paper will examine hob tool life and the many variables that affect it. The paper will cover the
state ofthe artcutting tool materials and coatings, hob tool design characteristics, process speeds and feeds,
hob shifting strategies, wear characteristics, etc. The paper will also discuss the use of a common
denominatormethod forevaluating hob tool lifein terms ofmeters[orinches] perhobtooth asan alternativeto
tool life expressed in parts per sharpening.