Angular contact pair bearing question

The spindle on my Barber Colman 1 - 1/2 gear hobber (table top hobbling machine) uses a pair of 15x32 mm angular contact bearings. My spindle has about 0.005 inch end play, so I assumed the bearings were worn out or the adjustment was off. After taking it apart I am puzzled by the arrangement.

The bearings are not worn out to extent of 0.005 inch play.

The installation is odd. Unlike the angular contact pair on my mill (or any other angular contact pair I am familiar with), which has an adjustable lock ring to set the preload, this installation has a sleeve between the bearings that the inner races are snugged against, which prevents the inner races from being adjusted, and leaves the 0.005 inch endplay.

The bearings are high precision so I am puzzled that Barber Colman would use such expensive bearings and then have an installation with so much play, especially in a machine that is advertised as being able to cut as fine as 250 pitch gears, which has a tooth height of 0.009 inch. 0.005 inch play with a 0.009 inch cut would render the part unusable.

Before I start modifying parts, does anyone have any thoughts on the problem?

John

Shim washers ?

Larry S
Fort Wayne, IN

Was the machine warm when you measured? That arrangement with the sleeve is not uncommon, but in my experience it has been made to exactly the same length as the seat to seat length for the outer race, and used with universal bearings (preload ground into the faces). Only reason I ask if the machine was warm is that an old friend of mine who worked in a hobbing shop for years said they wouldn't use the machines until they had run for a good half hour to hour. Still seems odd to count on things moving enough to take up that much play and create the proper preload.

Does it have only 1 sleeve
how are the outer races retained
With universal bearings the distance between the bearings have to be exactly the same on the inner and outer races
So it is very commen to have 1 sleeve on the inner and 1 sleeve on the outer race with exactly the same lenght and parralel within 0.002mm or so
On a precision bearing that is
Perhaps you are missing the sleeve on the outer race

Peter from Holland

The precision spindle tech's worst nightmare. Someone has monkeyed with with a precision spindle and reassembled it wrong or omitted parts. Barber-Coleman back in the day made machine tools the equal of the best. They would not put out a work or tooling spindle unless it was dead accurate.

I suspect someone took it apart and re-assembled it omitting a spacer, installing dud bearings, assembling not-DU bearings backwards - or something. You will have to look over the situation and reseach the topic of angular contact bearing pairs until you can diagnose the problem; probably after employing first principal thinking. Someone expert will have to paw through the parts and measure and ponder until the missing parts are determined and obtained or manufactured and the proper sequence of assembly is restored. Got the manual with an EPD and parts list?

Care has to be exercised when removing angular contact bearings. If they are pulled the wrong direction the inner race can pop over the sill of the outer race spilling the balls. This is a near disaster. Even if you capture all the balls their order is lost. They are graded for size to the micro inch and installed alternately around the separator; small to large to maximize load sharing Few shops have the equipment to measure balls to this degree of refinement. Random re-assembly reduces the bearing life considerably but it may not seriously affect the axis of rotation. YMMV.

This is not a problem to be solved by committee vote, consensus, or by long distance. Good luck.

Look for wear where the outer race seats(endplay type wear)

Thank you all for your help.

With regard to the bearings falling apart, they did. Oh well. At almost $600 for a new pair, I'll deal with the improper ball placement. I am only making delrin model helicopter gears with this machine, Module .7 to 1.0. The millionth or so additional runout caused but the ball placement I'll live with. However, I never knew that about ball placement and if I ever take a part a machine that it matters I'll be very careful. I only paid $300 for this whole machine.

I am not missing any parts, based on the Barber Colman parts diagram, so I don't think there were any shims at initial build.

I think the last post got it, wear of the outer race seats in the quill. The quill is soft steel, and this machine was used heavily over its life and not very maintained, and I think I can see a very small ridge where the bearing outer race transitions from the 32 mm portion to the beveled edge.

I cannot find 32 mm 0.001 shims that will work, so I can't shim the outer races.

My solution was to remove the inner spacer, and just tighten the lock ring down until no play. I then put Loctite 290 on the lock ring so it won't move. The inner races of the bearings are a very snug fit on the spindle, so even if the lock ring loosened I don't think the inner races would move.

Thanks again, I got my machine running again.

Anyone need a gear let me know.

Barber Colman #3 - any gear up to 200 teeth (including primes)
Barber Colman 1-1/2, any gear (sorry no primes above 72, but for a 1 inch gear max I think I am ok!)

John

Need a 32mm shim. Hmm 32mm = 1.259; a tad bigger than 1 1/4"

Here's a link http://www.onlinemetals.com/merchant.cfm?id=1217&step=2&top_cat=0

where they offer shims you can sandwich between washers and machine to OD and ID. PITA but it does a neat job.

They sell assortments too.