Re: [CAD_CAM_EDM_DRO] Re: Vertex Rotary Table Backlash

Thank you, John,
it is very clear now that worm gear is the best solution!
Regards, Alex

----- Original Message -----
From: stevenson_engineers <john@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, May 26, 2003 5:18 PM
Subject: [CAD_CAM_EDM_DRO] Re: Vertex Rotary Table Backlash


> >--- In CAD_CAM_EDM_DRO@yahoogroups.com, "alex" <telecomt@t...> wrote:
> > >
> > > Because you need the high worm ratio to prevent cutting forces
> > > driving the table. Try turning a 10:1 gearbox the wrong way, it's
> >not
> > > that hard and to get a high enough ratio that would prevent run
> >back
> > > on chain or belt would be an enormous ratio and physically
> >impossible
> > > to fit in.
> >
> > Thank you for the explanation, but for this, brake can be invoked!
> >
>
> Not if you are using the table for continious cutting. A brake is Ok
> for plain indexing if you can rely on the braking action not to jog
> the spindle.
> If you are continious cutting then the cutting forces can ans will
> move the table.
> The very first indexing head I built was made from an old headstock
> off a lathe with a big type 42 stepper of 1100 oz/in driving the
> spindle thru an 8:1 reduction arrived at by running a 10 T timing
> sprocket against an 80 T sprocket. This was heavy duty stuff, 3/8"
> pitch by 1" wide belt.
> First job was milling a face cam on the front of a 2" diameter bar
> with a 1/2" cutter. As the cutter started getting into the cut which
> was not excessive you could hear the motor loosing steps.
> I managed to do the job by just taking very light cuts and once
> finished promptly scrapped the head and went onto converting a big
> dividing head.
> See pic near the botton of this page.
> http://www.jeffree.co.uk/DivisionMaster/Examples.html
>
> John S.
>
>
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