Re: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????

I had the same problem, Kim and I conversed recently on this. My 48" length
Nook 3/4" x 0.2 screw is over a quarter inch out of straighness. When you
roll it across a table it makes a nice "wallop wallop" sound as it hits
highs and lows. I contacted McMaster and they indicate the tolerances per
the manufacturer, I cannot remember them all, but I believe they stated a
0.01 inch per foot number for straighness. That makes mine over 10x out of
tolerance. Ditto on the overnighted replacement, it's exactly the same. The
problem will be more a hassle on my situation, since both ends will ride in
bearings. Will have to find a way to bend it back more straight I guess.

R. William Kichman, P.E.
Kichman Engineering Associates
103 Old Furnace Road
Cornwall, PA 17016-0643
tel/fax 717/270-0714

----- Original Message -----
From: "Carlos Guillermo" <carlos@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, August 11, 2003 12:18 PM
Subject: RE: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????


> Hi Kim -
>
> Can you measure the bend? What kinds of numbers are you seeing?
> Or, are you assuming they're bent because the ballnuts are
> jamming? I ask this because I've heard that the pitch variation on
> rolled ballscrews can be enough to cause jamming if there is no
> compliance element between the two nuts.
>
> Regards,
>
> Carlos Guillermo
> VERVE Engineering & Design
>
> -----Original Message-----
> From: Kim Lux [mailto:lux@...]
> Sent: Monday, August 11, 2003 8:48 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Bent Nook ballscrews ?????
>
> Hi people.
>
> We've purchased a couple Nook ballscrews, one directly from Nook
> and the
> rest from McMasterCarr. All the ballscrews were slightly bent.
> An
> email friend of mine purchased one from McMaster Carr and had the
> same
> thing.
>
> On Friday I increased the tension on our Z axis zero backlash ball
> nut
> mounts. It worked OK for the machining we were doing then.
> However
> today we are machining a different, longer part and we found that
> the
> ballnuts are jamming on the screw, probably due to the bend.
> (There is
> no foreign matter on the screw, etc.) Backing the tension off the
> preload cured the problem.
>
> I'm not sure that there was a backlash problem when I tightened
> the
> preload on Friday. The parts coming off the lathe were spot on
> for
> tolerance.
>
> This bent ballscrew issue bothers me.
>
> Does anyone else have this problem ?
>
>
> --
> Kim Lux <lux@...>
>
>
>
>
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