Spindle Bearing Preload for Double Row Angular Contact Bearing??

catalytic · Apr 27, 2017

I am replacing the spindle bearings on a little Rusnok (Chicago) mill.

The manual says that the lower spindle bearing is a "preloaded double row ball bearing." The original is a New Departure 5204 (same as SKF 3204) double shielded bearing. I believe it's just ABEC-1.

I cannot see any way that the preload is applied. The inner race is coplanar with the outer race, and as far as I can tell, tightening the two nuts that hold the spindle into the quill would not apply any preload (it just means that there is pressure on both sides of the outer race).

Is there any reason not to replace it with a standard 5204 (SKF 3204) double row bearing?

EDIT:The bearing's inner race is marked New Departure 5204 on one side. On the opposite side of the bearing, the outer race is marked "New Departure 5504". The 1943 New Departure Handbook says that 5504 is just a single shielded 5204, but my bearing is double-shielded. Here are the specs from this 1943 handbook:

New Departure Hand Book ... - General Motors Corporation. New Departure Division - Google Books

Here are the spec's on the replacement:

Angular contact ball bearings, double row - 324 A-2Z

Here's the spindle with the bearings on it (between the bearings is a spacer tube that covers the actual spindle):

Here's the parts breakdown of the spindle:

new_guy · Apr 27, 2017

does the inner race have a radial split in it?

eKretz · Apr 27, 2017

The preload should be set when the nut is tightened with the spacer between the bearings. The inner races should be independent and they grind them so that when the faces are tightened into contact against each other the preload is correct. Do NOT replace with a plain double row ball bearing.

RC99 · Apr 27, 2017

Would I be right in saying your mill dates back pre around 1950?

Used to be back then and before some bearing manufacturers made precision double row angular contact bearings that somehow where assembled preloaded and ready to install.

Early Logan lathes used similar bearings along with I suspect round dials Monarch 10EE's(for the rear bearing), essentially they were specials and have not been made for decades and decades. There is a bit of info out there on the net about Logan lathe spindle bearing issues and how simply replacing the bearings with common ones does not work.

Looking at your diagram, I cannot see how you could preload the bearing in any way, and hence I guess the bearing is an unobtanium special.

muckalee · Apr 27, 2017

Note item number 1. the sleeve length sets the preload.

adama · Apr 27, 2017

If you can get a size combo that fits it should be easy to replace the doubles with two universal matched angular contacts though to make it back into a good spindle may just need to shorten the long spacer tube a bit.

bjmh46 · Apr 27, 2017

RC99 is exactly right. Preload has to be built into the assembled double-row bearing, and as stated, this was an available bearing back in the day. Having come from a machine tool design background, I have used these bearings (52xx) in the distant past. Also bear in mind that the 5200 series was furnished in two geometries: externally converging contact angles (analagous to DB mount for duplex), and internally converging contact angles(like DF mounting, and probably not suitable for lower spindle bearing.)

Bob

ewlsey · Apr 27, 2017

muckalee said:
Note item number 1. the sleeve length sets the preload.

No it does not. The only way preload could be set with a spacer is if there was a pair of concentric spacers. The preload is built into the bearing.

catalytic · Apr 27, 2017

bjmh46 said:
RC99 is exactly right. Preload has to be built into the assembled double-row bearing, and as stated, this was an available bearing back in the day. Having come from a machine tool design background, I have used these bearings (52xx) in the distant past. Also bear in mind that the 5200 series was furnished in two geometries: externally converging contact angles (analagous to DB mount for duplex), and internally converging contact angles(like DF mounting, and probably not suitable for lower spindle bearing.)

Bob

Is there any way to know for sure, or to locate a correct NOS or new replacement? I believe my machine dates between 1960 and 1979, but they continued to build these machines until at least 2012.

The bearing has "5204 printed on the inner race and 5504 printed on the shield. The new departure handbook of 1943 doesn't mention anything about built-in preload -- here are the specs (maybe no longer accurate at the time mine was made, as it states that 5504 is a single-shielded 5204, but mine is double-shielded):

New Departure Hand Book ... - General Motors Corporation. New Departure Division - Google Books

Jim Williams · Apr 27, 2017

I recently acquired a Derbyshire vertical micro mill. The spindle bearings felt very rough. A pair of bearings with preload ground in were at the collet end, with a single bearing at the draw bar end. I removed the snap rings holding the bearing shields in place, and washed out the hardened lubricant with mineral spirits. I relubricated the bearings with Kluber spindle grease and assembled the spindle. It now turns smooth and quiet. If you are lucky, the Rusnok bearings may respond the same.

Jim

ratbldr427 · Apr 27, 2017

eKretz,mucklee and newguy are correct.The spacer stacks the inner races together against the lower shoulder on the spindle when the upper nut is tightened.The upper bearing floats a little and does not tighten against the upper shoulder,the spacer is long enough to keep the inner races from touching the upper shoulder.
When the inner races of each bearing are pressed together the internal clearance reduced to zero and whatever preload is ground in.

RC99 · Apr 27, 2017

catalytic said:
Is there any way to know for sure, or to locate a correct NOS or new replacement? I believe my machine dates between 1960 and 1979, but they continued to build these machines until at least 2012.

The bearing has "5204 printed on the inner race and 5504 printed on the shield. The new departure handbook of 1943 doesn't mention anything about built-in preload -- here are the specs (maybe no longer accurate at the time mine was made, as it states that 5504 is a single-shielded 5204, but mine is double-shielded):

New Departure Hand Book ... - General Motors Corporation. New Departure Division - Google Books

There is nothing to say the bearing is original.

If the bearing is stuffed (and it may just need a good clean and regrease). then other then having the one in a billion chance of finding a new original bearing, the only other option is to modify to fit something else.

There are manufacturers or double row bearings with preload, but not that I know of in the same dimensions. The German bearing manufacturer UKF is one such company. There are other other bearing designs out there as well. Although I expect they all would be very pricey.

catalytic · Apr 27, 2017

RC99 said:
There is nothing to say the bearing is original.

If the bearing is stuffed (and it may just need a good clean and regrease). then other then having the one in a billion chance of finding a new original bearing, the only other option is to modify to fit something else.

There are manufacturers or double row bearings with preload, but not that I know of in the same dimensions. The German bearing manufacturer UKF is one such company. There are other other bearing designs out there as well. Although I expect they all would be very pricey.

Thanks again for the info.

I believe the bearings are original. The lower spindle retaining nuts appeared to have never been opened; the bearing markings also match what a friend had on his 2 Rusnok heads; and all 6 bearings in various parts of my machine are New Departure.

One oddity: New Departure handbooks say that preloaded versions of bearings will be marked with a suffix, i.e. 5204L or 5204M for Light or Medium preload. Mine just say 5204 and 5504 on various sides -- no suffixes.

I know how to clean double-shielded bearings, and I can get some Kluber, but how would I actually regrease it? Can it even be pulled off the spindle by its outer races without damaging it, or should they be regreased in place somehow?

Jim Williams · Apr 28, 2017

To put new lubricant in the bearings, I carefully washed and dried my hands, and then applied globs of grease to the balls and retainer. Using my fingers I worked the grease into the spaces between the balls. Kluber is not necessary, I simply had some on hand for my Deckel GK-21 spindle.

Jim

catalytic · Apr 28, 2017

Jim Williams said:
Using my fingers I worked the grease into the spaces between the balls.

My spindle bearings are double-shielded with metal shields, so I doubt I'll be able to push grease in with my fingers. I was thinking more along the lines of using a vacuum chamber or something to suck or push new grease in past the shields.

Mcgyver · Apr 28, 2017

if the 3204 are the right size, its probably what it you want. SKF has to be the most user angry site there is, I mean try and wade through the BS and find out what the class the 3204 comes in. Every time I have to F around with it I see red

In response to the ever-demanding performance requirements of modern machinery, SKF developed the SKF Explorer performance class of rolling bearings.

SKF Explorer angular contact ball bearings realized this substantial improvement in performance by optimizing the internal geometry and surface finish of all contact surfaces, redesigning the cage, combining the extremely clean and homogenous steel with a unique heat treatment and improving the quality and consistency of the balls.

how about Fuck off and tell me if they are P4 or ABEC 5 or whatever

Anyway, as has been said, the preload is set by whoever made the double row bearing - unlike individual ACB where you grind spacers or buy matched pair. The SKF double row has to have some preload (otherwise what would be the point). Wade through the BS site or call them. double row are not usually the highest standards of precision but I'd be surprised if SKF's weren't better than ABEC 1.....if they're say 5 that is probably good enough. ABEC 7 or P4 is better...not sure if double rows come in it though (from SKF)

Johnny SolidWorks · Apr 28, 2017

ewlsey said:
No it does not. The only way preload could be set with a spacer is if there was a pair of concentric spacers. The preload is built into the bearing.

Looks like item 27 is the outer race spacer to me, although the drawing is less than ideal, and I don't know a thing about these machines. So I could be way off.

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