Re: Re: backlash reduction

In a message dated 01/25/2000 7:50:06 PM Hawaiian Standard Time,
jmelson@... writes:

<< I have about .001 - .002" backlash on all axes, and I really can't tell
where
it is coming from on any of the axes. The X and Y are used precision
ballscrews, though, so it could easily be wear. But, the Z screw is new.

Any thoughts, anyone?

Thanks,

Jon

>>

Jon,

Everything on a knee mill is cantilevered. I'm amazed we get the accuracy
we do. If I have a test dial chucked in the spindle and touching the bed and
then push down on the front of the knee, I can see .001 or more. This is with
all axis locked. I guess this is why jig borers are never set up as a knee
mill. More of a gantry or bedmill setup.

I have to adjust my Y axis on my series 1 Bridgeport at least once a
year. I can see the ways loosen up with the DRO. The table crabs and makes
the DRO reading stall or go back a thou when changing directions. I suppose
the quill could cock just a smidgeon to show the same .001 backlash reading.
I would indicate the head casting to quill clearance and have the CNC move
the quill up and down slowly. You may see more side to side movement than
you'd like. And/or back to front.

Lightly used manual mills will die faster than a heavily used CNC if
there is no one shot or auto lube. I strongly believe in the Bijur oilers
ability to resist rapid wear and thus looseness in machine tools.

Peter