RE: [CAD_CAM_EDM_DRO] My ballscrew / bearing block design.

A couple more questions...

I picked medium preload because light went from 0 to X lbs of preload. I
wasn't sure that would guarantee no backlash. Will a light preload
generate a no backlash setup?

I'm sure I learned about shrink fits at some point in my machine design
class but that was 15 year ago...If I shrink fit a piece on the ballscrew
and then machine it will it "loose its grip and slip" (obscure reference
to 'you ain't got a hold on me' - AC/DC)?

Is there a technique for getting the required surface finish for the
seals? I was also wondering about the hardness required for them. I was
contemplating just putting speedi-sleeves on these portions of the shaft.

Thanks,
M


leslie watts said:

> Yeah, 15 mm would be fine.
>
> I can certainly understand the desire to make a shrink fit insert
> though. I machine ballscrew ends...and if you make a mistake...expensive
> scrap! Also, even annealed 41xx alloy is not the most fun for cutting 32
> tpi.
>
> Unless you have a good cylindrical or tool post grinder I would suggest
> making the adapter out of 1144 "stressproof" alloy. It's pre hard (100,000
> psi
> yield) but cuts like butter. Shrink fit will be fine...about.0002 to .0005
> interference.
> Cross pin it with a recessed taper pin.
>
> The bearings should be a press fit on the shaft too. I would leave the
> adapter od
> in the bearing area .0005-.001" oversize...since there is some ambiguity
> about the
> final diameter after shrink fitting. Then sand or stone down (in the
> lathe)
> to about
> .0002" above the bearing id.
>
> Oh, one other thing comes to mind....medium preload db pairs will work ok,
> but light
> preload (5% of max dynamic) will be fine. It's a little lower friction.
> Use
> 20-40 degree
> contact angle. I use 40.
>
> But in general, your design seems very sound. It should work well. Nice
> drawings too.
>
> Les
>
>
> Leslie M.Watts
> L M Watts Furniture
> Tiger Georgia
> (706) 212-0242
>
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