Re: [CAD_CAM_EDM_DRO] Re: Toothed pully design information needed.

In a message dated 11/11/2000 7:18:49 AM Hawaiian Standard Time,
Smoke@... 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. I'm thinking that you could
start close to these values, index cut all the teeth and check fit.

If not good, then index and recut the teeth say .0025 inch or something
deeper till you do get a good fit. Will take a while but you should get a
good part. I would radius the profile cutter at the tooth root as it will
make dirt and debris more likely to be expelled by the sprocket.

Peter
THRD, Inc.


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