Bearing clearance

[MrsEsterhouse]

I have a Gear box that I am getting contradicting opinions on. The output shaft has a spherical roller bearing on it with a spec internal clearance of .005 to .008 in. If i push on the shaft I get .001 axial movement, which is to the gearbox manufacturers spec.
When I pull up on the shaft it moves .008 in. Which my gearbox manufacturer says is too much. The OEM bearing that the gearbox came with was an SKF. When I contacted their technical department they said they would expect that sort of movement in their bearing.
Which one is right? Has anyone else had any similar experiences? Am I even in the right part of the forums?

Thanks

 

[hydtools]

I would believe SKF. They should know their product.

If the gearbox manufacturer says that's too much, then they have a design problem. They spec'd the wrong bearing.

Make sure you and both manufacturers are talking about and measuring the same parameter as they each understand it.

Ted

 

[ccw]

Is the gearbox operating in a manner that fails to meet expectations? Are the clearances just a curiosity or a hunch about performance or performance deterioration? When you said "pull up" you did not give a direction? Is this a vertical shaft or horizontal shaft you are exercising? Do you have another unit in-house, in the store room, or on the vendor's shelves that you can compare to? To classify those clearances one should know at least the shaft bore and housing OD of the bearing.

 

[MintJulep]

So you have a total of .009 axial play in the shaft?

The bearings are new, or used?

The bearing is pressed on to the shaft?

How is the bearing retained in the casing?

 

[oliebol]

Are the axial forces on your output shaft bi-directional?

If not, you can fill up the tolerance zone in one direction and eliminate the excessive clearance necessary for your bearings, but damaging your gearteeths.

If so, there are certain types of bearings which have smaller than average clearances. Or use a different combination of bearings

Greetz Martin

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[diskullman]

Did you replace your bearing with one of a higher internal clearance? This will vary between standard fit, C3, and C4.

Russell Giuliano

 

[Tmoose]

I don't have specs for speherical roller bearings in front of me, but the ratio for axial>radial clearance for taper roller bearings is lot of axial for barely any radial.

There will likely be some Bearing OD to housing clearance. Unless the outer ring is clamped or other precautions are taken that clearance is readily available during a "lift" test if the dial indicator base is grounded to the bearing housing or beyond. Is your "up" test in the radial shaft direction?