Re: [CAD_CAM_EDM_DRO] Re: Bearing question for ballscrew conversion

Standard lead accuracy from RBS is .007"/ft cumulative. 1"X.250 lead is
$29/ft. Thomson is .004"/ft for about the same price. RBS will QC it to
.003/ft for an extra $11/ft.

Or you could buy the RBS nuts and Thomson screws. RBS admits they are
interchangable.

Doug

----- Original Message -----
From: Ward M. <wardmerk@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, May 22, 2001 2:47 AM
Subject: RE: [CAD_CAM_EDM_DRO] Re: Bearing question for ballscrew conversion


> That sounds like a good price. What is the price and lead accuracy for
the
> screw stock?
>
> Thanks,
>
> Ward M.
>
> wardmerk@... <mailto:wardmerk@...>
>
>
>
> -----Original Message-----
> From: Doug Harrison [mailto:prototype@...]
> Sent: Monday, May 21, 2001 5:57 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Bearing question for ballscrew
> conversion
>
>
> > To increase rigidity even further, a RIGID mount is used. This uses a
> > spacer BETWEEN each pair of angular contact bearings. Shims are
> > usually used for "fine tuning" this type of setup.
> >
> > A properly designed fixed-fixed (or rigid-fixed; or rigid-rigid)
> > setup is NOT over-constrained.
>
> I just perused the Rockford ballscrew catalog and came up with a nice
chart.
> RBS shows four arrangements and gives end fixity factors for determining
> critical speed:
>
> fixed-free = .36
> simple-simple = 1.00
> fixed-simple = 1.47
> fixed-fixed = 2.23
>
> The constant is in a first order term so you can see what a difference end
> restraint can make.
>
> I did the calcs on 10ft. screws and decided to rotate the nuts instead.
>
> By the way, if you are looking for preloaded nuts you can't beat RBS for
> price. They quoted $171 each for 1"X.250 lead, whereas Thomson quoted
$950.
> Both were single track. 5/8" was about $145 - not worth building your own
> for that.
>
> Doug
>
>
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