Backlash measurement

All gears need backlash so the gears do not bind. The backlash can be cut on only one gear or both gears. Backlash is obtained by making the tooth thickness less than the calculated value.  If you are using a gear cutter there is nothing you can do for backlash because it is built into the gear cutter. The backlash will be whatever the cutter makes it.

When making a gear blank, DO NOT make the blank bigger, a little small is OK. The exception to this is if you are making a long addendum gear. Long addendum gears are used when the center distance has to be a bit bigger than usual. If you are making a long addendum gear to gain 10 thou on the center distance then make the blank 20 thou over the calculated diameter and sink the cutter in to the calculated whole depth plus 10 thou.

The distance measured as above should be less than the calculated distance. The difference is the backlash (tooth thinning). This measured backlash is for the gear you are measuring. Check the meshing gear for its backlash and add the backlash for both gears to get the backlash for this gear set (the working backlash).

NOTE how many teeth to measure over is specified and does change depending on the number of teeth on the gear.