Re: Timing belt pulleys -- manufacture

--- In CAD_CAM_EDM_DRO@egroups.com, "Smoke" <Smoke@5...> wrote:

> A question or two for you John:
>
> When you machine the cutter, is it REALLY necessary to put a radius

on the

> bottom? Wouldn't a flat bottom with nearly square corners give more
> clearance?
>
> It would appear a cutter made as indicated above could then be used

to cut

> ANY size (number of teeth) pulley. Is that correct?
>
> Smoke

First Question:
No there is no real need to put a radius at the bottom as nothing
runs there. The only reason this was done was
[a] reduce any stress at the root of the pulley teeth - and
[b] more importantly on the cutter any sharp edge is susceptible to
wear and problems in hardening.

Second Question:
We only made one cutter to do from 12 up to about 70 teeth with no
service problems.
Commercial pulleys are usually hobbed and the blank is made slightly
oversize so that the hob cuts the whole of the circumferance. This is
to ensure that the radius blends into the outer diameter and you have
no sharp edges.