Re: BP variable speed questions

--- In CAD_CAM_EDM_DRO@y..., "Smoke" <smoke@t...> wrote:

> If the damage isn't too severe, you could simply clean up the

existing

> keyways in the shaft and sheave and make a custom fitted key. The

slightly

> oversized key would add a bit of strength as well.
>

I thought of that, but my minset said no because I kept thinking I'd
buy the keys. The keys are made of Delrin with a steel inner key. I
suppose I could machine new delrin keys that are larger, along with a
larger steel inner key...

> For the Pulleys, you could use multiple step pulleys. This would

give you an

> even wider range of options for the speed control. If your taking

the head

> apart anyway...why not count the teeth on all the gears, make

yourself a

> sketch and calculate what all the existing ratios are?
> That would be a good FIRST step.
>
> Smoke
>
> > I am in the process of rebuilding the variable speed drive in my
> > Bridgport Series I CNC, and am trying to make a decision in

regard to

> > the worn front pulley parts. The keyways are worn in the pulleys

and

> > hub. I'm thinking the easiest (and cheapest) way to repair the

hub

> > and shives are to press the hub out and cut new keyways on the
> > opposite sides of the hub and the shieves. The Bridgeport parts

guy

> > I deal with was very adament about not doing that, saying the

balance

> > would be upset, and the old keyway would quickly damage the delrin
> > bushings as the shives slide up and down the hub. I'm not sure

if I

> > buy that one, especially since he's the one trying to sell me new
> > parts. Can anyone see anything wrong with cutting new keyways?

Is

> > there a special procedure to press the hub out of the bottom

shieve

> > without galling it?
> >
> > The other thing I thought of was since I am going to be using a

VFD

> > to drive the motor, maybe it wouldn't be a bad idea to eliminate

the

> > top variable speed components altogether with fixed-size pulleys.
> > That would seem simpler and quieter. However, I haven't any idea
> > what would be a good ratio to choose for the pulleys to be able to
> > get high and low speeds. I don't have a manual for the machine,

so I

> > don't know what the reduction is for the back gear (low speed).

Its

> > also my understanding that torque shouldn't be affected by using

the

> > Mitsubushi VFD's at low speeds--is this true?
> >
> > Appreciate any help.
> >
> > Bob
> >