FIXING A PRACTICAL IDEA In your January issue.

FIXING A PRACTICAL IDEA

In your January issue, the access "Idea pulls tooth form from sketch" (p 86) needinesss a little rescuing. Three errors may leave a certain number of of your readers confused.

First, the chordal thickness is listed as 314 instead of the correct 0314 secondary root diameter, instead of the correct base diameter, is cited as the origin of the crushing angle. From that point, a tangent to the base circle, an arc which approximates the bend of a generated involute can be sketched. Note the first drawing (Fig. 1) of the author's gear and using his technique.

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