Re: Timing Pulley Accruacy and Servo shaft runout

Ron,

I counted on your reply...

Sure, you don't want to bore off center; did I say that was a good
idea?!?

What I said was that tolerances stack up, and you can SOMETIMES
reduce them by adjusting the relationship between the parts.

And that doing so, WHEN YOU CAN; is a good idea.

Ballendo

P.S. With most any stock, non precison bored pulley that's being
held by a setscrew or two, there WILL be an offset. The small timing
belt pulleys folks use for reduction are horrible in this respect.
I'm talking about the aluminum and plastic timing belt pulleys from
sources like SDP and Boston Gear. Sure, IF a person has the machine
shop that you do; they can bore 'em out and/or insert a precision
sleeve. And not need to do what I've suggested. I'm guessing that
more than a few guys here do NOT have that capability; either in
machinery or in skill and knowledge required.
As you correctly say, "Everyone has there own ways of doing things."

>In CCED, R Rogers <rogersmach@...> wrote:
> ballendo <ballendo@...> wrote:
>Now I'm going to disagree with an original reply here; which said
>you did not want to try to compensate for your shaft runout with
>the pulley--by turning it upon the shaft before locking it down.
>
>It is a VERY good idea to do such things when you can. Tolerances
>are tolerances, and they DO stack up. If you can adjust some part
>of that stackup to reduce its overall value, it's a good thing.
>
> Ballendo
>
> //That was probably my post you are referring to. Everyone has

there own ways of doing things. First of all, in mounting something
on a shaft for concentricity this is a no-no. Simply boring the
pulley off center to accomodate for shaft run-out is not a "fix". If
the reason of the run-out is the shaft being bent(more than likely),
not only is there runout, the shaft is also angular to the true axis
of the device. Now bore a pulley off center however, the bore is
parallel to the OD. The pulley, even though now concentric, will
wobble.

>
> If the motors are new, I'd return them. Or find a replacement.

If those aren't an option and If it bothered me enough, I'd remove
the armature dial it up between some centers and straighten them in
a press. If it's only a few thou run-out and it being a milling
machine, I'd just use them and not worry about it, unless it causes
a problem. My guess, it won't.

>
> Ron
>
>
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