Re: Toothed pully design information needed.

--- In CAD_CAM_EDM_DRO@egroups.com, ptengin@a... wrote:

> In a message dated 11/11/2000 7:18:49 AM Hawaiian Standard Time,
> Smoke@5... writes:
>
>
> > Let's see...without even using a book, I would figure the OD of a

3/8" pitch

> > timing belt pulley having 40 teeth as follows:
> >
> > 40 x .375 / PI = 4.774648....diameter. From this I would simply

use a

> > cutter made like John mentioned as cut the tooth profiles using a

dividing

> > head.
> >
> > Does that sound reasonable?
> >
> > Smoke
> >
> >
>
> Smoke,
>
> Sorry, it is not that simple. The pitch line of the belt is about

halfway

> through the thinnest portion of the belt. So, the OD of the pulley

is about

> 4.774648 minus the ~~ thickness of the belt. These are the elusive

numbers /

> formulae that Wanliker and Alan cannot find.

These figures are now published in most books. I had to work these
out for myself back in 79 - 80 as there were no published figures
then.
To get the PCD of the pulley you take the pitch x No of teeth divided
by Pi
So from Smokes figure above his answer is correct.
The outside diameter is then the PCD MINUS a constant which for a
3/8" pitch pulley is 0.030" so the OD will be 4.745"

See the thread called Tooth Pulley design - Manufacture