Angular contact bearing clearance?
Angular contact bearing clearance?
(OP)
I have a couple of questions to ask regarding a double row angular contact bearing that we are intending to use in a flat belt tensioner.
The bearing in question is a NSK 32BD219DUK. For reference the size is – 35mm x 55mm x 20mm and has a nominal internal clearance of 47 microns. Single piece outer & single inner & seals on both sides
The application for the bearing is to be used in a timing belt tensioner set up where a solid shaft will be press fitted into the inner race and a sleeve press fitted onto the outer race to bring the overall diameter up to 60mm. The bearing assembly will have a stationary inner race/ rotational outer that will apply tension to the back of a timing belt.
The question that I need to shed some light on is the clearance of the bearing regarding weather or not the bearing needs to be in a preloaded state or not. This can be adjusted by the amount of interference that the shaft and housing will produce. I have been told that angular contact bearings need to have a certain amount of preload to perform correctly. Is this correct?
The reason why I have to ask this question is that NSK produce a timing belt tensioner that has this bearing installed in a similar layout to the one that we are designing, and as they have no stock of the bearing at present, I obtained a number of these tensioner units to use the bearings as a stop gap. When checking the clearance of the NSK tensioners it was found that several units have a clearance of up to 20 microns and several others having zero. I can only presume that the tolerances of the bearing diameters and the shaft & housings that have been made are accumulating the manufacturing tolerances so that certain units had clearance and others had none – therefore putting the bearing into preload, hence my question regarding preload!
The other thing that will probably be a deciding factor is that the operating temperature will be approx 120 degrees C
Sorry for the long (1st) post! but would greatly appreciate any input on the above.
Thanks
The bearing in question is a NSK 32BD219DUK. For reference the size is – 35mm x 55mm x 20mm and has a nominal internal clearance of 47 microns. Single piece outer & single inner & seals on both sides
The application for the bearing is to be used in a timing belt tensioner set up where a solid shaft will be press fitted into the inner race and a sleeve press fitted onto the outer race to bring the overall diameter up to 60mm. The bearing assembly will have a stationary inner race/ rotational outer that will apply tension to the back of a timing belt.
The question that I need to shed some light on is the clearance of the bearing regarding weather or not the bearing needs to be in a preloaded state or not. This can be adjusted by the amount of interference that the shaft and housing will produce. I have been told that angular contact bearings need to have a certain amount of preload to perform correctly. Is this correct?
The reason why I have to ask this question is that NSK produce a timing belt tensioner that has this bearing installed in a similar layout to the one that we are designing, and as they have no stock of the bearing at present, I obtained a number of these tensioner units to use the bearings as a stop gap. When checking the clearance of the NSK tensioners it was found that several units have a clearance of up to 20 microns and several others having zero. I can only presume that the tolerances of the bearing diameters and the shaft & housings that have been made are accumulating the manufacturing tolerances so that certain units had clearance and others had none – therefore putting the bearing into preload, hence my question regarding preload!
The other thing that will probably be a deciding factor is that the operating temperature will be approx 120 degrees C
Sorry for the long (1st) post! but would greatly appreciate any input on the above.
Thanks





RE: Angular contact bearing clearance?
information, and speed as to whether it
should be preloaded or have clearance.
Unless rigity is the main concern, often
clearance is allowed to reduce the turning
torque and reduce the heat build up in the
bearing. I assume the bearing manufacturer
specified the bearing and clearance for
your application.
RE: Angular contact bearing clearance?
RE: Angular contact bearing clearance?
For double-row angle contact bearing, axial preload is already established when the bearing is manufactured.
Fit is also an important parameter.
At this page you will see NSK's recommendation for shaft fit for thrust bearings such as double-angle contact:
http://www.tec.nsk.com/Handbook.asp?menu=7,0,0,0&PageID=/FitsAndInternalClearances/ThrustBearingsAndShafts.html
To convert the letter into recommended shaft/bearing bore interference go here:
http://www.tec.nsk.com/Handbook.asp?menu=7,0,0,0&PageID=/FitsAndInternalClearances/ShaftsAndInnerRings.html
At this page you will see NSK's recommendation for housing fit for thrust bearings such as double-angle contact:
http://www.tec.nsk.com/Handbook.asp?menu=7,0,0,0&PageID=/FitsAndInternalClearances/ThrustBearingsAndHousingBores.html
To convert the letter into recommended outer ring/housiong clearance go here:
http://www.tec.nsk.com/Handbook.asp?menu=7,0,0,0&PageID=/FitsAndInternalClearances/HousingAndOuterRings.html
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RE: Angular contact bearing clearance?