How are cutter numbers interpreted for Gleason No. 16 and 26 machines?
Gleason spiral bevel cutter numbers are usually specified with a combination such as #9 – 20 and a point width. In this example, #9 – 20 indicates that the cutter’s nominal Pressure Angle is 20 Degrees. The “#9” indicates the equal but opposite deviation of both Inboard (IB) and Outboard (OB) cutter angles from the nominal 20 Degrees. If we consider a #0 – 20 cutter, the differences between each IB / OB angle and the nominal PA would be 0, so that IB and OB angles would both be 20 Degrees. In other words, the cutter profile would be symmetrical. Cutter numbers other than #0 are not symmetrical; that is, the IB and OB cutting angles differ in a plus/minus amount about the nominal PA. Visualize the blades as tilted either inboard or outboard in the cutter body. The blades have the same PA, but the IB and OB angles are changed. For example, if a 20Deg PA cutter IB angle is 21D 30M, its OB angle would be 18D 30M. The IB / OB differences are +/- 1D 30M. A positive cutter number means that t
