Editing Rack and pinion (section)

== Geometry ==
The teeth of a rack and pinion pair may be either straight (parallel to the rotation axis, as in a [[spur gear]]) or [[helical gear|helical]]. On the pinion, the profile of the working tooth surfaces is usually an arc of [[involute]], as in most gears. On the rack, on the other hand, the matching working surfaces are flat.  One may interpret them as involute tooth faces for a gear with infinite radius.  In both parts the teeth are typically formed with a gear cutter (a [[Hobbing|hob]]).<ref name="agma"/>