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

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

Main page:
http://www.lmwatts.com
Engineering:
http://www.lmwatts.com/shop.html
Cnc surplus for sale:
http://www.lmwatts.com/forsale.html
Carved signs:
http://www.lmwatts.com/signwp.html


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com]On Behalf Of PPC
Sent: Monday, November 07, 2005 9:16 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] My ballscrew / bearing block design.


I am no expert on this but looking at your website and perusing Hiwin's
catalogue, here are some info that hopefully will be useful:

1) Your ballscrew diameter of 3/4" is about 19 mm.
2) You were saying that you felt using a bearing of 15 mm ID maybe too
small.
3) Looking at Hiwin's spindle end dimension for 20 mm ballscrew, they
recommended using bearing 7302BTVP or 6202 for 15 mm spindle end.

So, maybe it is safe enough to use bearing with 15 mm ID and no need to go
thru all those troubles.

Weedy

----- Original Message -----
From: "Tony Jeffree" <tony@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, November 07, 2005 2:37 PM
Subject: Re: [CAD_CAM_EDM_DRO] My ballscrew / bearing block design.


> At 06:33 07/11/2005, you wrote:
>>I spent the past week or so working on a bearing block design for my
>>conversion. I am documenting my project on http://www.cncwright.com
>>and I put some screen shots up. I got ballscrews that were only 3/4"
>>in diameter and have been trying to figure out a way to mount them in
>>bearings bigger then 15mm ID. I am thinking about shrink-fitting an
>>adapter on the end of the ballscrew that will also me to make the
>>diameter bigger. I'm not too sure about shrink fits and would be
>>interested in any tips, information, or alternate ideas.
>
> Alternatively, why not:
>
> - Sleeve the ID of the bearing; or
>
> - Use smaller bearings?
>
>
> Regards,
> Tony