Posted by BillS on September 24, 2008 at 12:28:24:

In Reply to: Re: worm gear angle posted by David Petzer on September 23, 2008 at 11:17:58:

Here's the formula I use for worm angle, which is the same as worm gear angle:

Angle = ARCTAN{ starts / [(OD - 2/NDP) x NDP] }

Where OD is the worm OD. (OD-2/NDP) is a calculated pitch diameter for worm where addendum is 1/NDP. If you know the actual pitch diameter, just substitute pitch diameter for (OD - 2/NDP).

This may not be the exact same angle as the cutter angle, even if cutter has same hand and starts, since you want to use a cutter with OD slightly larger than worm OD.