What is the trial and error method to find the differential formula for my gear hobber?
This is another approach if you just can’t find your formula any other way. Desperation calls for desperate measures… (preferred ways are listed above). First we must have two known, quality helical gears with at least a 2″ face. Okay, a shorter face will work, but a long face means more accurate results. These gears must have different teeth. The bigger difference, the better. Why two? There is the matter of hobber type that must be determined. Hobbers are designed two ways: either to cut by lead, or by helix angle. These two types of machines (I call Types A and B) use different formulas according to their design. Next we need a dial indicator that reads .0001, or in “tenths”. It should have a lever stylus with ball tip. This will be mounted on the cutter table and set to indicate at a line approximately half-way down a tooth profile. The pitch and helix angle of both gears must be known. They don’t need to be the same from gear to gear, but must be known quanties. The plan is to m
