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radial clearance in bearing

radial clearance in bearing

radial clearance in bearing

We have a centrifugal water pump, 2900 rpm speed. The water temperature is 20-30 centigrade degree. In original design (KSB Germany) this pump has two 6413 C3 bearing with 0.023-0.043 mm radial clearance. Now we can't find C3 bearing. Can we use CN (0.008-.0.028 mm radial clearance) bearing by change the bearing seat tolerance on shaft/housing? The shaft tolerance on shaft is 65k6 (+0.002, +0.021m) and in housing is 160K6(-0.021,+0.04mm).now we use induction heater for mounting bearing on shaft. Thank you

RE: radial clearance in bearing

Basically what the "C3" designator means is that the bearings were supplied with extra radial clearance.  I recommend asking the pump vendor why they went to this extra step before going with the normal bearing.  Also, have you checked that you can't get the bearing special made with the C3 clearance?  While it may not be off the shelf, a quick Google search indicates it should be possible.

Patricia Lougheed

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RE: radial clearance in bearing

As Patricia has said - contact the manufacturer with your enquiry, make sure you give them the operating conditions including the operating temp so they can review the bearing change.    

International College
Naresuan University

RE: radial clearance in bearing

Have you tried to contact the bearing manufacturer (SKF) directly?  KSB uses SKF ball bearings in their pumps (some KSB factories may use FAG bearings).

Also, the bearing number you provided indicates that it is a single row bearing.  Be certain this is correct and that either bearing isn't a dual one.


RE: radial clearance in bearing

If you havent got time to wait for a response, then perhaps you could select wide clearance CN bearings by measurement.
According to your tolerance figures, CN goes up to 0.028, while C3 goes down to 0.023
Perhaps you will be lucky.
I would resist the temptation to adjust the interference fit, as a spin will possibly wreck the shaft or housing.
Remember a tighter fit may mean a shorter life; watch the running temperatures.


Steve McKenzie

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