Re: Timing Pulleys

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:

>
>
> kadeshan wrote:
>
> >Does anyone have a part number for an xl pulley with a 5/8 in

bore?

> >Or something slightly smaller. Also what ratio would you

recommend,

> >its on a bench knee mill, using 600 oz in servos. They X axis is
> >already done with a flexible coupling. ANy getting any good

results

> >cnc the knee on something similar?
> >
> >
>
> >I can tell you I bought all my timing pulleys with the smallest

bore,

> >
> and bored them out on the lathe. I was appalled at how poor the

centering

> of them was. I saw up to .020" runout on them, and that was from

W. M.

> Berg, a pretty high-class manufacturer.
>
> Jon

I have purchased steel, all nylon, and nylon with an aluminum hub.

The steel seemed fine, but since I needed a 1" ID, I bored it out
before testing it. the ID did not have any obvious runnout.

The all nylon was pretty bad, it was not just runnout, but was also
off axially makeing it not only appear to move up and down (runnout)
but also wobble. That was a 72 tooth and since I needed to bore it
it didn't matter.

For the large unit, I made a steel hub, bore it to 1 inch and then
put a step on it of 1.5". faced and bored the timing gear with a
1.5 inch and pressed it on the hub. Then bolted them together.

I have had more smaller 16 to 32 teeth nylon with aluminum hub.
those have been about 50/50. I've been fortunate enought that I have
often needed one for the motor and another for a larger shaft so have
to bore one anyway.

In this case, I think you get what you pay for, and if I had received
a Berg that was bad, I'd contact cust service and get a new one.

Dave