On Thu, 1 Dec 2005 14:21:32 -0500, "Terry Keeley" tkee(no spam)@(or
mail)rogers.com wrote:

.
Just out of curiosity, were the originals bb or ff? My first take on
it would be to replicate the original setup.


Thanks for the help but someone installed regular standard ball bearings so
I don't have any history to go by.



Ive not removed bearings from your particular mill..but based on most
angular contact bearings...they should be mounted like this " "

With a hand snug preload.

I recently got into a beef with a well known CNC lathe manufacture
over angular contact bearings.. A brand new machine became noisy on
the Z axis after about 6 hours use. I tracked the noise down to a
thrust bearing between the ballscrew and the servo motor. Taking it
apart...I found the bearings to be mounted . They were
toasted..brinelled.

The bearings and their housing came pre assembled from a major high
quality bearing manufacture and not only did the machine become
nosiy..but z repeatability was all over the map...up to .0035+
variations.

The manufacture claimed it was the first time this was found..and
frankly they didnt believe me...so they sent out a their own tech to
check..and he replaced the bearing cartridge. Gee..suddenly it was
quiet and most of the repeatability issues went away.

2 days later..I had to replace a ballscrew and thrustbearing on a much
older machine made by the same manufacture. I pulled the bearing
housing apart on a lark..and found the bearings to be

I mentioned it to the customer..and he said he had always had an issue
doing a back turn.....

I suspect they really dont want to know about the second bearing I
found ..as it may open a can of worms they dont want opened. Shrug.

I figured that some gomer in Japan had too much saki and kereoki the
night before and assembled em wrong. The second bearing means there
are likely to be more bad ones out there....

All parties shall remain nameless.

Gunner



I can order bearings that are ground and sold as a matching set in either
"b
to b" or "f to f" that when mounted together and the retaining nut
tightened
give a "light preload".

I can also order bearings that are not matched but are for "universal
pairing" that are about half the cost and are made to mount either way.
Some posts on the Yahoo Group mention that to apply a preload to these
bearings a shim is needed between them either on the inner or outer race,
others say none is needed. If the bearings are made to mount either way
how
can they be preloaded without the use of a shim? If needed how thick
should
it be?

If you do this without any shims the bearings will have way too much
clearance I suspect. What bridgeport used to do was to grind the face
of the bearing race to set this, rather than use shims, on the M heads.

My first take would be to order the same type (bb or ff) as the original
bearings, and purchase them as a true angular contact pair.

Jim

Think this might be the way to go also but most don't seem to go this
route...




--
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please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
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"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner