12.9 Thinning for backlash

It is customary to ignore backlash when determining the addendum modification coefficients x1 and x2, i.e., x1 and x2 are usually nominal values corresponding to zero backlash. The small adjustments (radial shifting) of the generating rack for tooth thinning are indirectly defined by specifying the amount the pinion and gear teeth are thinned for backlash, Δsn1* and Δs n2*. With this convention, the outside diameters of the gears are independent of the tooth thinning for backlash, and are based solely on the addendum modification coefficients x1 and x2. The root diameters will be changed with the tooth thinning, sinze the tool is moved further into the material.

Tolerances for the maximum and minimum values can be entered using the plus button PIC at the side of the field.


Figure 12.4: AGMA 2001/2101 - Tooth thickness tolerance