Bridgeport spindle bearing replacement

[wbleeker]

Hi all has any one got a good assembly drawing of the spindle and quill for a Bridgeport J head, mine had noticeable runout so I replaced the bearings, I put everything back together the same way it was thinking that would be the end of the runout, I ended up with 8 thou runout, thinking I had a bent spindle I took it to be repaired when they checked the spindle they could find nothing wrong with it.I think maybe the previous owner of the machine may have put the bearings in the wrong way around or something silly like that.My Bridgeport is one made in England by Adcock-Shipley but I think everything else will be the same as the American made ones

Thanks in advance
Will Bleeker

[Rotate]

What kind of bearing? Some of them require preloading which is important. How tight was the bearing-quill fit and the bearing-spindle fit. The replacement bearings should be either ABEC7 or ABEC9. Also, I find the type of lubrication has an effect on the smoothness of the bearing, although this should not affect the TIR.

Albert

[Thrud]

Will how did you check it for runout? This should be measured after about 1/2 hour of the spindle running to insure proper warmup. runout should be checked on the spindle itself and not referenced against collets or face mills as they can be slightly out of round.

Attach an indicator to the head itself and with the power off the indicator should run on the R-8 taper in the opening of the spindle - note reading, rotate 90* - note reading, rotate 90* - note reading, rotate 90* and read again. Last reading should be same as first if not make sure all the indicator supports are tight and repeat the four readings.

[MESC]

Regarding your Bridgeport Bearings. If you buy a MATCHED SET of ANGULAR CONTACT BEARINGS you do not need to shim(PRELOAD) the bearings. They are expensive. I bought the cheaper NON MATCHED SET (PAIR THATS 2)bearings once again angular contact and cut a shim out of a coke can. It was the perfect thickness for my machine and also one of my mates bridgeports also. At high RPM I back of the bottom bearing collar a LITTLE for those eight hour mill days cutting aluminumn.

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[wbleeker]

Albert, yes the bearings are ABEC7, the bearing quill fit is a sliding fit, the bearing spindle fit a light press fit, I am not quite sure if the bearings were in the right way because I only put them back the way they were and the head has definately been pulled apart before.
Thrud,I checked the runout with the machine cold I did put the indicator in the spindle opening but didn't do it how you said.
MESC I only bought the non matched pair because I didn't know you could buy a matched pair, took the bearing shop 2 weeks to get them as it was they hadn't heard of a Bridgeport and they are at Port Kembla centre of the largest steelworks in Australia.Hw did you work out that you needed a shim,how did you work out the thickness and where did you put it.
Thanks again
Will Bleeker

[dellinger1140]

Will, I have a Bridgeport operators manual that came with my 1957 Bridgeport. It has an assembly drawing of the J head and a parts list. I could scan it and email it to you if you think it will do you some good. Wayne

[wbleeker]

Wayne
I have already got a J Head drawing that Randy sent me a couple months ago but I can't make out the quill/spindle details very well, perhaps your drawing is a better one. if you would email it to me at [email protected] I would be very grateful
Many thanks
Will Bleeker

[wbleeker]

Got to spend a couple hours on the machine today looking at Waynes drawing the top bearing is a double row angular contact, mine only had a single row radial contact bearing does anyone know if this is right or should I have the doudle row angular contact for the top and what is its number.Anyway I assembled the spindle with bearings and spacers on the bench I did the nut up pretty tight and then I put the dial indicator on the bottom bearings there was no movement in either of them, I thought everything was right so I put the spindle back in the machine and then tried the indicator again .0035 runout. I am thinking that if the top bearing is the wrong one perhaps there is a bit of radial runout that is being accentuated by the distance from the other two bearings and that this in turn may be causing the runout at the spindle nose - any ideas anyone.
Will Bleeker

[Thrud]

wbleeker:
The double row bearing should go (I would think) near the spindle nose where it is needed for radial and vertical thrust loads. the top bearing should just stabilize the rear of the spindle and remove any play (preload length) in the housing.

The greatest forces are near the nose of the spindle.

[NAMPeters]

The only image I have of a J-head is an exploded view which is not clear as to assembly of the parts. Does anyone have a x-section drawing they could e-mail me? Angular contact bearings are fussy as to how they are installed, one way gives a wobbly shaft and another way gives a rigid shaft. Matched sets give you an etched V image on the outer race showing how the bearings are mated. There also should be markings indicating the thrust face of each race.

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Neil Peters

[wbleeker]

Thrud,I have two single row angular contact bearings for the nose end of the spindle, which according to Waynes cross sectional drawing go in back to back,this drawing also shows the top bearing as being a double row angular contact bearing,the bearing that was in my machine when I got it was a single row radial.My machine was made in 1964 Waynes drawing is a 1957 model does anyone know if my head should have the double row top bearing or was this a design change.
Will Bleeker

[Thrud]

wbleeker:
Maybe you should contact Bridgeport and ask them the proper sequence just to be sure - can't hurt.