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Bearing Geometry - Bearing Torque || Dynaroll

TECHNICAL PAPERS

TECHNICAL PAPERS

DESIGN FACTORS WHEN USING SMALL BEARINGS, PART 1: BEARING GEOMETRY (Page 6)


The ball moves higher in the raceway (bigger contact angle). the contact ellipse becomes smaller for a given applied axail load.


This leads to some simple rules in designing for lower torque.

Factor Torque effect
Ball size Smaller gives lower torque
Number of balls Fewer gives lower torque
Radial play Higher gives lower torque
Applied load Higher gives higher torque

Of course, there are other factors, such as choice of lubricant and retainer type that also effect torque, but the above are the rules for bearing geometry considerations.

The chart below can be used as a simple guide to expected average torque levels for individual bearings with oil lubricant, however, the user must be cautioned that real-life torque values will vary considerably according to the application.
Average Bearing Torque (GM-CM)
DYNAROLL BEARING SIZE (Inch Series)
RETAINER TYPE
BALL SIZE
# BALLS
THRUST LOAD (gm)
MAX AVG TORQUE (gm-cm), OIL LUBE @ INDICATED THRUST
RADIAL PLAY inches (mm)
MC2
.001-.003
.002-.008
MC3
.002-.004
.005-.010
MC5
.005-.008
.013-.020
9,0,1,1-4,1-5
144, 155, 156, 168
Crown (W)
# 1/16
# 13
75
.18
.15
.14
2-5
Ribbon (J)
1/16
6
75
.18
.15
.14
2-6, 2, 166
Ribbon (J)
1/16
# 8
75
.18
.15
.14
188
Ribbon (J)
2
8
400
.63
.54
.49
3
Ribbon (J)
3/32
7
400
.65
.55
.5
4
Ribbon (J)
3/32
8
400
.7
.6
.55


Conclusion

This article is supposed to be a general introduction to bearing geometry issues in miniature single-row deep-groove radial ball bearings. More detailed information, including formulae used and a deeper discussion of bearing issues is available from dynaroll.com.
Design Factors, Part 2 -Bearing Mounting and Fitting, Page 1 link