Re: [CAD_CAM_EDM_DRO] Re: Stepper mount for Vertex H/V 6" rotory table ?

At 08:20 03/05/2003 +0000, you wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Tony Jeffree <tony@j...>
>wrote:
> > At 02:54 03/05/2003 +0000, you wrote:
> >
> > > > For the 6", I would not go below 200 oz-in or thereabouts. The
> > >Vertex
> > > > tables, despite having ball races on the worm shaft & on the
>table
> > >spindle,
> > > > seem to need a fair amount of power to drive them. May be
>something
> > >to do
> > > > with the grease they lube them with.
> > > >
> > > > Regards,
> > > > Tony
> > > >
> > > >
> > >
> > >Tony,
> > > I have a 6" Vertex and can not get a 200 oz in motor to turn
> > >it. The stepper is a Pacific Scientific Powermax II. I have taken
> > >all the backlash adjustment to where it is very free running, but
> > >still no luck.
> >
> > Suggest you try cleaning out all of the bearing surfaces & re-
>lubricating
> > with a light machine oil - see if that makes a difference.
> >
> >
> > Regards,
> > Tony
>
>When I set up my 4" Vertex table (from Tony !), I found that the worm
>shaft was not free to turn in the eccentric bush that engages /
>disengages the worm. I had to ream the bush to get a good fit before
>it was suitable to 'show a stepper' - maybe Vertex has a
>manufacturing problem in this area. Both parts looked well made, but
>I suspect that either the shaft was very slightly warped or the bush
>was oval. Either way a VERY small shaving with a reamer sorted it in
>10 minutes.

I've just spent a bit of time "preparing" a 6" table to take a motor mount.
They seem to like using a particularly thick & chewy grease on the worm &
wheel, and contrary to the exploded diagram that comes with the table, none
of the bearings are ball races - they are all cast iron-to-cast iron or
cast iron-to-steel. Removing all traces of the grease and using a light oil
in its place significantly improves things. The end-float adjustment on the
worm shaft is pretty crude (simple threaded set screw collar, with set
screws that bear on the threads on the worm shaft!); one of the major
sources of friction comes from this arrangement, and it is important not to
be too agressive about removing all traces of end-float. I found that
"running in" the worm shaft bearings by hanging a power drill on the shaft
and running the drill for a few minutes took all the high spots off, and
rendered it much smoother and easier to turn. This will also be benefit the
other bearing surfaces.

The final thing that is worth doing is checking the end-float adjustment on
the table itself, which is achieved via a plate in the base of the table.
There are 4 cap screws that adjust the end float, and 4 set screws that
operate against the cap screws to lock the setting. Disengage the worm and
see how free to rotate the table is; if this is stiff, try adjusting the
end float, or again, do some "running in" to lap the surfaces against each
other.

It is interesting to compare the torque needed to drive the Vertex type of
plain bearing construction with the 4" Sherline table, which uses ball
races on the worm shaft and a ball race at the base of the table. You
definitely need around 200 oz-in to drive the Vertex (both 4" and 6"),
whereas I have a Sherline table that will work very nicely with about 60 oz-in.


Regards,
Tony