Ball Race Type Bearings

[PaulR]

I need to use a small sealed ball race (for a shaft of 3 or 4mm) for the current project but I've never used them before so I have two questions:

1 how is the shaft fixed, a push fit, Loctite or is it just free?
2 how is the race itself usually fixed, a push fit, Loctite or a retaining screw?

[PaulR]

ChatGPT gives this answer which sounds reasonable. Since I'll be using silver steel for the shaft and a ready-made bearing, I'm guessing it won't be a tight fit out of the box so I'll probably have to use Loctite to fix the shaft to the inner race and a retaining screw to hold the unit in place.


"With sealed ball race bearings (like deep groove ball bearings with seals or shields), the inner race and outer race must rotate relative to each other, but only one of them should rotate — not both.

Here’s how it’s usually arranged:

The inner race is designed to be fixed to the rotating member (usually the shaft).

The outer race is fixed to the stationary housing (or vice versa, depending on the design).

Typical fitting practice:

The inner race is usually a light interference (push) fit on the shaft.

This ensures it rotates with the shaft and doesn’t slip.

The exact fit depends on load direction and precision requirements — often something like an H7/k6 or H7/m6 fit.

The outer race is generally a sliding or transition fit in the housing, unless the outer race is the rotating part (then the situation is reversed).

Adhesives:

Adhesive (e.g., Loctite bearing retainer) is sometimes used if the fit is slightly loose or if you want extra security, but it’s not normally the primary method.

In most designs, mechanical interference is preferred.

Never free to turn:

The shaft should never be free to turn inside the inner race — that would cause wear and galling, quickly ruining both the shaft and the bearing.
The intended relative motion is between the inner and outer races only, via the balls."

[uuu]

Yes, that sounds good.  Frighteningly good.

Many bearings in manufactured assemblies have a tight enough fit in the housing and on the shaft not to need adhesive or screws.  If you find your fit is good enough, you may be able to dispense with these too.

If your design has axial thrust on the bearing, then the collar on the shaft and the step in the housing may provide additional friction on the races to assist in preventing rotation.

Wilf

[PaulR]

Yes, that sounds good.  Frighteningly good.

Many bearings in manufactured assemblies have a tight enough fit in the housing and on the shaft not to need adhesive or screws.  If you find your fit is good enough, you may be able to dispense with these too.

If your design has axial thrust on the bearing, then the collar on the shaft and the step in the housing may provide additional friction on the races to assist in preventing rotation.

Wilf

Thank you - I'd rather rely on human input that AI (but that that was only part of the answer, it offered masses of detail about ISO standards for fits and goodness knows what else!).

[john mills]

some time the inner bearing is allowed and must creep around on the shaft example is stub axel  working on rollers the roller will
have bearings and the shaft will also be mounted on bearing so it can rotate fits depend on use  .if its push fit or tighter press
it is no use wasting lock tight just in case as it is wiped off  it must have room.for small bearing light push fits would be good

[PaulR]

some time the inner bearing is allowed and must creep around on the shaft example is stub axel  working on rollers the roller will
have bearings and the shaft will also be mounted on bearing so it can rotate fits depend on use  .if its push fit or tighter press
it is no use wasting lock tight just in case as it is wiped off  it must have room.for small bearing light push fits would be good

Thanks John, I'll have to see what the fit is like once the bearing arrives.

[tghs]

a drawing or photo of your application would help,, yes bearings and shafts can gall and seize.. also think about circlips and grooves to locate bearing,,
 

[PaulR]

a drawing or photo of your application would help,, yes bearings and shafts can gall and seize.. also think about circlips and grooves to locate bearing,,
 

Cheers. I haven't got as far as designing that part of the engine yet but it'll be very simple with just the sealed units held in vertical standards.

[uuu]

It may become a key element in your construction to ensure the bearing housings in the standards are truly in line.  Perhaps you could make them just undersize and ream them together in a test assembled form.  Likewise, if this is a crankshaft, having the ends lined up.

Wilf

[PaulR]

It may become a key element in your construction to ensure the bearing housings in the standards are truly in line.  Perhaps you could make them just undersize and ream them together in a test assembled form.  Likewise, if this is a crankshaft, having the ends lined up.

Yes, I've taken to doing lots of things in pairs recently to ensure alignment.