Re: Driving a Bridgeport Knee

Hay, I know just what you mean. I have been agonizing over these
same points for months. But the one thing I know for sure, is a
powered knee for Z if defiantly the way to go. I have no wish to
loose my manual spindle.

There are a lot of choices to make for knee power, and it comes down
to time, money, and what accuracy you can live with.

Wally





--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
<polaraligned@o...> wrote:

>
> Well, I don't think they get it very much below .001". You will
> have backlash to contend with. But the bigger question is how
> accurate are those gears anyway? People get ground screws over
> rolled ones- yet settle for sloppy bevel gears? I just like the
> idea of driving the leadscrew directly and saving the bevel gears
> for manual operation of the machine. I may even get a ballscrew
> for the Z axis, but I have not really decided if this is just a

waste.

> As it is all commercial conversions (that I have seen) drive the

quill

> because it is more accurate. To each his own...
>
> Scott
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me" <cnc4me@g...>

wrote:

> >
> > Well for what it is worth, the people i talked to about driving

with

> > bevel gears said to shim them and take out the backlash.
> >
> > Wally
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
> > <polaraligned@o...> wrote:
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me"

<cnc4me@g...>

> > wrote:
> > > >
> > > > I was wondering if this was feasable also, if my machine

wasn't

> > > > buried under a ton of stuff i would investigate further.

While i

> > do
> > > > not have any answers i do like hearing your ideas or anyone

elses

> > on
> > > > the subject. One thing i am affraid of with usaual methode

of

> > > > driving the knee, is breaking the bevel gear with to much
> > > > horsepower...
> > > >
> > > > Wally
> > > >
> > >
> > >
> > > I really am resistant to driving through the bevel gears as they
> > > are very sloppy. I also like to be able to move all axis by

hand

> > > should the need arise or for the "quickie" machine job. My

machine

> > > is currently completely apart for a rebuild, and I can see no

reason

> > > why this won't work. Just can't bring myself to drive through
> > > the damn bevel gears....
> > >
> > > Scott
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > >
> > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Polaraligned"
> > > > <polaraligned@o...> wrote:
> > > > >
> > > > > I am thinking about driving the knee with a pulley just

below

> > the
> > > > > bearing on the Z-axis leadscrew. I would machine the

leadscrew

> > down
> > > > > to accept the pulley. The motor would be mounted on the

side

> > of the
> > > > > knee, and to get the timing belt out I would cut a

rectangular

> > slot
> > > > in
> > > > > the side of the knee.
> > > > >
> > > > > Advantages:
> > > > > Motor is out of the way.
> > > > > I can still use the handle to move the knee via the bevel

gears.

> > > > > (can't leave the handle permanantly attached!)
> > > > >
> > > > > Disadvantages:
> > > > > Lose about 2 inches off the bottom of the knee travel
> > > > > Changing belts would be a real pain in the you know what.
> > > > > Permanantly alter the knee with hole (which does not bother

me)

> > > > >
> > > > >
> > > > > I think the motor will have no problem with clearances.
> > > > > Does this sound good? or am I missing something.
> > > > >
> > > > > Scott