Posted by BillS on November 02, 2009 at 14:22:31:
In Reply to: Re: Please help Gear calculations posted by Andy on November 02, 2009 at 10:03:11:
Colin is the right guy to crunch the numbers; I just want to point out something about guessing at the helix angle:
Helix angle is correctly measured at the pitch diameter. For a "normal" gear, that is about half-way down the tooth. If you look only at the top of the tooth, the helix angle will appear larger. This difference is exaggerated for a small number of teeth.
One good way to measure is to put a pin in a tooth space that touches about half-way down and measure the angle on the pin (It's also easier to use a protractor with a pin than looking at the tooth space).