Re: How to measure helix angle of sample gear?


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Posted by Bill on March 08, 1999 at 13:30:08:

In Reply to: How to measure helix angle of sample gear? posted by Chu Kee Tong on March 08, 1999 at 11:22:57:

There are a number of machines (new & used)called "lead Checkers" that do what you want. Gear lead is related to Helix angle as follows:

LEAD = PI x TEETH /[NDP x SIN(Helix angle)]

If the gear is standard pitch (or module) it is also possible to closely approximate a sample's helix angle by calculation. Knowing NDP, measured OD, and number of teeth:

Helix Angle = ArcCosine{Teeth/[(NDP x OD) - 2]}

(ArcCosine looks like COS-1 on a calculator keyboard and is the 2ndF of COS key)

If Module is known, find NDP as 25.4/Module.

HTH,
Bill




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