RE: [CAD_CAM_EDM_DRO] Ballscrew end mounts was Re: Doesnt ANYONE have this drawn up???

Vince,

I think you may have the wrong one....
The file name is endbearing.DXF.

It is not highly detailed but is to scale. I have
dimensioning turned off.

The main purpose with this is just to show exactly how
the commercial units are constructed. This one is 17mm
bore, but others might be different depending on ballscrew
size.

In this design (as is typical) steel bearing retaining rings
also serve as replaceable seal mating surfaces. Locknut torque
is not terribly critical because the bearings are universal flush
ground for a light (5%) preload. This simply means that the bearing
inner rings are actually very slightly recessed compared to the
outer ones. When the locknut is tightened the inner rings
of the pair deflect until they come in contact. The deflection is just
the proper amount to give that specified preload. Further
tightening of the nut does not increase the preload any further.

One has to hunt up bearing fit tables for the exact housing
bore and shaft diameter dimensions.

Here are numbers for 7203 from the MRC bearing engineering
handbook:

shaft: 0.0000"-0.0007" interference in bore ABEC-1
0.0000"-0.00035" ABEC-7

housing:
0.0000"-0.0011" loose ABEC-1
0.0000"-0.00055" loose ABEC-7

I find ABEC-1 is fine for most ballscrew setups.

Bearing contact angle can be 15-40 degrees depending
on load requirements. Many even use deep groove bearings
with a higher than normal radial clearance. This causes them
to actually operate as angulars with a few degrees contact angle.
Several machines in my shop use this as an economy measure,
but shims or spacers must be used since deep grooves are not
normally supplied with universal flush face grinding. I prefer
40 degree angulars for ballscrews though.

A final note: for this size range it is reccomended that
the bearing bore/shaft interference be limited to 0.0002"
to facilitate assembly and disasembly without possible
damage to the expensive ballscrew. The upper ranges of
the fit tables don't really consider this, and the bearings
can be almost impossible to remove without damage in
this kind of assembly.

Les

Leslie M.Watts
L M Watts Furniture
Tiger Georgia USA
http://home.alltel.net/leswatts/wf.html
Engineering page:
http://home.alltel.net/leswatts/shop.html
CNC surplus for sale:
http://home.alltel.net/leswatts/forsale.html
CNC carved signs:
http://home.alltel.net/leswatts/signwp.html




-----Original Message-----
From: Vince Negrete [mailto:vnegrete@...]
Sent: Sunday, August 17, 2003 12:30 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Ballscrew end mounts was Re: Doesnt
ANYONE have this drawn up???


Oh that one? Here lemme copy name here...

Simple Shaft Bearing Mount.JPG
An easy way for mounting and adjusting shaft bearing supports

Is this the right one?