spindle bearings

Hello

I have dismantled a Jones and shipman Internal Grinder spindle, I am going to rebuild it with new bearings, But I am a bit confused, at the rear pulley end of the spindle it has one Bearing, at the front of the spindle it Has two bearings mounted together, but what has confused me , is that only one of the bearing is actually fitted to the spindle, they both are press fit into the body of the spindle casing .

Anybody have any ideas

one thing I did think of , is it to do with radial load and Axial load?

lee

If you search online, you will find numerous arrangements illustrated:

This one is quite a good start: **LINK**

https://www.researchgate.net/figure/The-coupling-dynamic-model-of-spindle-bearing-system-supported-by-both-angular-contact_fig13_321688545

In quick summary … You need some controlled longitudinal ‘float’ to maintain the bearing characteristics when temperatures change.

MichaelG.

The arrangement linked to by MG is common for machine spindles, especially grinders. As well as providing preload it reduces over-constraint on the spindle due to multiple bearings.

Andrew

The left hand bearing is not prevented from moving to the left along the shaft. Probably an oversight in the schematic.

Thanks for the replies,

I looked at the drawing of the spindle in the link that MG posted, it's not very close to the one I have.

What I have is a spindle casing roughly 101mm in diameter , 230mm in length with a wall thickness of 9-10mm,

inside the casing at the front , is a recess to take two press fit bearings butted up together onto a shoulder , they are NOT angular contact bearings, which did surprise me also, but they are deep groove bearings, 30x62x16,

At the rear of the casing is another recess with a should , but the Single bearing , also a deep groove bearing 25x52x15mm does not directly press in there, instead it has what I would call a carrier, that the bearing is press into.

This carrier is a robust sort of component , imagine a extra thick walled piece of tube about 50mm long , it is machined out to carry the press fit bearing, all around the perimeter of the carrier is holes, in those holes are springs that stick out,

Down the outside of the carrier is a slot, that locates on a pin that protrudes to the inside of the casing, you push the carrier into the machined recess, tight but it is a smooth fit , you do this after you have fitted the front bearings into the casing ,because of the design of the spindle shaft.

The spindle shaft itself , has a journal machined on the front to carry just one of the front bearings, remembering there are two pressed into the casing.

Here is another bit of a head head scratcher for me. There is two other journals on the spindle shaft, to carry a machined thick walled tube , it moves very smoothly on those journal , it's not pressed on , when the spindle is assembled everything done up, when you shake the spindle , you can here it moving up and down inside, I thought it was a spacer to push up against the bearings for preload, but it does not go up to the bearings ,it cant reach them, it's about 1/8 inch short, Is it there to stop vibration in the spindle?

thanks

lee

.

Sorry ..it was just meant to be illustrative of the sort of information you should be able to find using Google

Obviously you will have a better idea of what you are looking for

I simply searched for “grinding spindle bearing arrangement” [without the quotation marks] and set it to display images … then chose the one that I thought might help.

Hopefully you will recognise some version that looks more familiar.

MichaelG.

Michael,

No need for sorry mate, I appreciate any help I can get, I also scoured the internet for info on this particular spindle , but with no luck, I have rebuilt it now, but I not sure about that machined tube I mentioned moving about inside

Regards

lee

Lee,

I have just had a look in the parts manual for the 540 machines and the cross-sectional diagrams here show the spindle supported on two angular contact brgs, one at each end. The spring box arrangement is there to maintain a constant preload through the outer rings, regardless of thermal differentials.

You must have a bigger machine ?

Two bearings at one end is the sort of arrangement one might use if axial positioning of the shaft was critical. In theory since the use of a paired unit is there to provide preload, then only one of the bearings needs to have the shaft going through it in order to get the required radial support. This arrangement 'might' also save one having to worry about some aspects of matching the two bearings, but I have to say I have never seen such an arrangement in my life so I am intrigued. Inner rings should normally be clamped to the shaft by a nut. I cant see how this would be compatible with your arrangement though.

Can you make some kind of sketch ?

Gerry.

Sounds a very odd arrangement to me. Normally grinding spindles, both internal and external would have matched opposed bearings of some type at the business end. In my experience these would be angular contact and would be separated by a spacer and some spring type arrangement to take up the bearings as the spindle warms up and expands. I have never seen one fitted with deep groove bearings of the "normal " type. They are simply not accurate enough or precision use. I suspect the spindle you have has been messed around with at some point and has has these bearings fitted simply because the internal / external dimensions were the same.

Generally if you fit specialist bearings they tend to be wider and this might explain the gap in the spacer. Jones and Shipman made many different spindles over the years and the designs altered over time. They also made "specials" and you may ave one of those. However they would never fit bog standard deep groove bearings to a quality spindle.

As a side note angular contact bearings can be ordered as a matched set with a defined amount of preload. These are matched at the factory and I have used them on precision adjusters etc. where microns matter. However, they come at a price!!!!

Dont worry too much by the use of radial ball bearings. Essentially radial ball bearings and angular contact are same internally. When an axial load is put on radial ball bearings them they become angular contact. The size of the angle simply depends on the radial clearance within them. Typically for a 'C3' clearance bearing you will get 10 degrees or so of contact angle and this will increase depending on the load. When preloaded they run at about 15 degs contact angle. So provided these radial bearings are 'precision' made, they are just a lower cost arrangement than an angular contact set-up. But since radial bearings have fewer balls that ACs, they have a lower load capacity. This isnt a problem on a surface grinder though.

Gerry

Lee, I have sent you a pm.

Gerry