Re: [CAD_CAM_EDM_DRO] mounting ballscrews onthe ol mini mill help

Marcus,

Good point about the radial + ball thrust bearings. In fact INA
makes such sets!

As far as the other idea- yes it works fine! Usually called a "floating
nut".
The one pictured in my engineering web site is alowed to float a little
radially.

For end bearings this might be fine too. Let the motor handle the radial
part.
Depends on the set up I guess.

Ideally a leadscrew is a pure thrust device and would have no radial load at
all.

Les
Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.alltel.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.alltel.net/~leswatts/shop.html

----- Original Message -----
From: "Marcus & Eva" <implmex@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Wednesday, October 02, 2002 11:38 AM
Subject: Re: [CAD_CAM_EDM_DRO] mounting ballscrews onthe ol mini mill help


> Hi All:
> You can also split up the functions of the bearings by using radial
> bearings and putting separate ball thrust washers on the ends.
> It can be a bit screwy trying to figure out how to accommodate the extra
> bearings, but it's a method I've used with success on other kinds of
> applications where I needed good thrust capacity and couldn't get what I
> needed in a single bearing.
> In this application, an argument could be made that thrust capacity is
more
> important than precise radial running.
> The argument goes like this: so what if the screw flops around a bit
> radially...we care most about about eliminating backlash in the drive;
> that's why we went to all the trouble to get ballscrews.
> If the screw is free to flop around radially, it can self-adjust for
> misalignment between motor, screw, and nut.
>
> So....is this argument bullshit???: or does it have some merit???
> I await enlightened responses.
>
> Cheers
>
> Marcus
>
> ----- Original Message -----
> From: "Les Watts" <leswatts@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Wednesday, October 02, 2002 5:49 AM
> Subject: Re: [CAD_CAM_EDM_DRO] mounting ballscrews onthe ol mini mill help
>
>
> > Well, there isn't going to be much compression load on a 3/8"
> > screw.... it would buckle unless it was very very short.
> >
> > I think you could get away with regular conrad type ball bearings
> > if you deal with the axial clearance. Note that on these bearings
> > the inner race can move around axially quite a bit. This would cause
> > massive backlash. But you can use pairs preloaded
> > against each other. That really turns them into angular contact
> > bearings with a few degrees contact angle. They are spaced
> > with an inner and outer sleeve of slightly different lengths.
> > Do this on one end only.
> >
> > Ordinary deep groove ball bearings are rated for light thrust loads-
> > all bets are off if you get shock loads from a crash or something
> > though. But hey- these are $3 bearings.
> >
> > You can get single and double row angular contact and tapered
> > roller bearings easily at places like MSC, Grainger, and Reid
> > if you want. They can cost much more and yes might be hard to find in
> > such a small size.
> >
> > Les
> >
> > Leslie Watts
> > L M Watts Furniture
> > Tiger, Georgia USA
>
>
>
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