Re: [CAD_CAM_EDM_DRO] Re: Backlash

Mark Vaughan wrote:

> Hi Jon and Vince.
>
> My mill isn't a BP, it's much bigger and stiffer, built in 1989, and has low
> hours on it so no curved bed or wear in the screws.
>
> With the screws removed on mine the table is very hard to move, I mean very
> hard, a full body shove, even with the gibs loosened.

Something is very wrong, here. What way lube are you using?
The guides are all

> pressure oil lubricated and it runs with oil when operating. The table is
> very heavy, but not finger movement like Jons. Are you sure Jon it isn't
> this loose due to the wear?
>

No, my table is NOT loose. That is the way it is supposed to
be, gliding on a film of oil.

>
> I had a lube pipe fail to one of my screws so I stripped it to clean any
> debri out, check the balls were OK, so any bad ones could be replaced before
> the expensive screw was damaged and rebuilt it.

I replaced all the Bijur metering orifices on my lathe, as I
think one of them clogged up and that was why the bed was so
badly worn. They are not terribly expensive, considering how
important they are.

this all

> comes from the end radial bearings, and it is the same all the way along the
> bed. On my machine the bearing runs on ground ways, I have tightened then
> hand tight, I am sure if I tighten them more I can remove the backlash, but
> am unsure how tight to go.

I have mine set AMAZINGLY tight, way tighter than I would have
ever believed necessary. I'm guessing the axial preload has to
be 1000 Lbs! I really can't tighten the adjusting collar any
tighter with a large wrench. But, it had to be that tight to
remove the backlash/axial play. It depends a little whether
they are using angular contact ball bearings or tapered roller.
The tapered rollers can take huge force, the angular balls can
still take more than you'd guess.

Jon