Problem- Bridgeport S1 VariSpeed Head vertical spindle play

[Beezer]

I have discovered vertical play in the spindle on my BP Series 1 and need some help to diagnose what it could be.

With the quill in the fully up postion and quill lock engaged, I can push up on the end of the spindle with my hand and there is visible movement of the spindle upwards, inside the quill. It drops down when I release pressure from my hand. Could this be caused by spindle locknut being loose or a missing part?
I have never taken any part of the head or spindle apart but I recall someone at the company, that previously owned the mill, saying they had removed top portion of the head to do some maintanence on it and replace the drive belt.


I also find the VariSpeed head noisy when running, but that is a problem I will
tackle after I fix the spindle play issue.


Any input would be appreciated?

[polaraligned]

The nose cap sets the bearing preload for the spindle. Maybe it is loose. Spindle bearings also could be shot.

[Beezer]

Well I think I might have found the cause of the vertical play...well at least I hope I did? I removed the spindle and found that the locknut at the top was loose. Once I looked closer, I noticed one of the tabs on the lockwasher was broken off. Either the tab had broken off over the years or the previous owner of the mill had taken the spindle apart for some reason and might have broken the tab off.



I have noticed a gap between the long sleeve and the upper bearing, which I am not sure is suppose to be there and could use some advise on that.
(See photo #1)


Also, is there suppose to be any gap between the dirt skirt and the shoulder portion of the spindle? Mine seems to have a gap approx. 1/16".
(See photo #2)


The 2 lower bearings seem to be ok and run smoothly. However the upper bearing I will need to replace as it feels abit rough. Will I need to have the spindle taper reground if I am only replacing the single top bearing?

The pair of lower bearings are marked "ABEC MRC 2078 D 1" and they have a "B" scribed into each of them along with some other lines scribed in various locations.

The upper bearing is marked "FAFNIR M206K" and the manual shows the code no. for this bearing to be 1190237.

Any help would be appreciated.

[polaraligned]

I don know about the bottom gap. I think it is fine.
The top probably should not be there.

The top bearing is nothing special and you can get it inexpensively at a number of machine tool dealers. The bottom bearings (Spindle Bearings) are very expensive. They do all the work. The top bearing just stops that shaft from flopping around when it spins. The spindle bearings appear to correctly have the V's lined up that are scribed in them. If you do not replace these spindle bearings (Lower ones) then you do not need to regrind. The sleeves between the lower bearings must be ground to precisely the same length. If they are not, the spindle bearings will not preload properly. But you do not want to take off the spindle bearings to check this because you will ruin them by taking them off.

[polaraligned]

Remember, the threaded nose cap on the bottom of the quill that holds the spindle in is what sets the preload for the spindle bearings. You should be able to tighten it up to adjust for proper preload and have the nose cap fall just short of bottoming out against the quill.

[Beezer]

Ok Thanks. I will check with bearing supplier I always deals with for work and see if they can find a real good quality replacement bearing for me.

Seeing how the main spindle bearings seem to be just fine, I had no intentions to remove them. The nose cap looked to be just bottoming out before I removed it and the set screw was lined up with the recess in the cap as it should be. Now the the larger diameter sleeve, between the main spindle bearings, could move between the outer bearing edges, but it has a snug fit with no slop. Looks to be a real precision fit.

The rest of the spindle, along with the spline, looks to be in really good condition and doesn't appear to have been abused. Pretty good for a machine made in 1978.

Thanks for you help and I will post back the results once I get that bearing replaced and the spindle reinstalled.

[mactec54]

Beezer

There should be no gaps at either end,( it looks like some hack has been at this one) if you replace the top bearing, get a 2RS bearing, that means rubber sheilded, Because the top nut was lose, that might be why the gaps are there,get the correct wrench & do the nut up tight, & see if you can close all the gaps

[mactec54]

polaraligned/Beezer

The threaded nose cap has nothing to do with preload, it only holds the spindle/bearings into the quill housing, the preload is controlled/set by the 2 spacers between the 2 front bearing, once the nut at the end/top of the spindle is done up, then every thing is loaded, The nose cap should be done up tight & locked, as this stops the spindle from floating in the housing

[Beezer]

I got the old bearing off the spindle and I am going to bring it with me to the bearing supplier tomorrow to see if they have what I need in-stock.

Do I need to use the same brand of bearing to replace the top bearing or can I use a Timken or other good brand, if they have one with the same specs or better?


I tried to message NC Cams to see if he had the OEM specs on the top bearing, but his message box if full.


Since I can't trust whom ever put the locknut on the last time. Just wondering which way is the locknut suppose to be installed? Taper side up or down?

[mactec54]

Beezer

The nut should be taper down, the tabs should be up againist the taper away from the bearing face, & just use what ever tab finds a slot to lock it once you have it tight, most bearing suppliers will have a new lock washer if you need it

Any good quality bearing will do for the top bearing, but don't get the same as what you have (open Bearing ) get a 2RS as I said in the other post, For the bearing size you only need to measure the OD, ID & thickness,any good brand will do

Get the wrench when you are at the Bearing supplier, Don't beat on the nut with a punch, this nut has to be locked down tight, to hold all 3 bearings locked together

For (NC Cams) He is no longer with us, He will be missed

[Beezer]

Ok thanks.




Sorry to hear about NC Cams.

[Beezer]

Picked up a new SKF bearing for the spindle today and got it installed without any issues. Once the shaft was cooled down and the bearing warmed up, it just dropped into place. Tightened up the nut and locked the washer tab in place. All gaps are now gone and all bearings spin smoothly.

Just wondering if I would be able to regrease the main spindle bearings with them in place or should I just leave them?