Montage of Timken Bearing Products
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This is the most basic and most widely used type of tapered roller bearing. It consists of two main separable parts: the cone (inner ring) assembly and the cup (outer ring). It is typically mounted in opposing pairs on a shaft.
Unit of Measure

Specifications

Series

 N/A 31308

Cone Part Number

 N/A X31308M

Cup Part Number

 N/A Y31308M

Design Unit

 N/A Metric

Cage Material

 N/A Stamped Steel

Related Assembly Number(s)

 N/A 31308-90KA3

Dimensions

d - Bore

 N/A 40 mm1.5748 in

D - Cup Outer Diameter

 N/A 90 mm3.5433 in

B - Cone Width

 N/A 23.000 mm0.9055 in

C - Cup Width

 N/A 17.000 mm0.6693 in

T - Bearing Width

 N/A 25.250 mm0.9941 in

Abutment and Fillet Dimensions

R - Cone Backface "To Clear" Radius1 N/A 2.030 mm0.08 in
r - Cup Backface "To Clear" Radius2 N/A 1.52 mm0.06 in

da - Cone Frontface Backing Diameter

 N/A 52 mm2.05 in

db - Cone Backface Backing Diameter

 N/A 61 mm2.4 in

Da - Cup Frontface Backing Diameter

 N/A 86.40 mm3.40 in

Db - Cup Backface Backing Diameter

 N/A 75.95 mm2.99 in

Ab - Cage-Cone Frontface Clearance

 N/A 3.8 mm0.15 in

Aa - Cage-Cone Backface Clearance

 N/A 3.3 mm0.13 in
a - Effective Center Location3 N/A 4.1 mm0.16 in

Basic Load Ratings

C90 - Dynamic Radial Rating (90 million revolutions)4 N/A 26200 N5890 lbf
C1 - Dynamic Radial Rating (1 million revolutions)5 N/A 101000 N22700 lbf

C0 - Static Radial Rating

 N/A 88100 N19800 lbf
Ca90 - Dynamic Thrust Rating (90 million revolutions)6 N/A 37000 N8320 lbf

Factors

K - Factor7 N/A 0.71
e - ISO Factor8 N/A 0.83
Y - ISO Factor9 N/A 0.73

G1 - Heat Generation Factor (Roller-Raceway)

 N/A 22.9

G2 - Heat Generation Factor (Rib-Roller End)

 N/A 10.3
Cg - Geometry Factor10 N/A 0.091
  • 1 These maximum fillet radii will be cleared by the bearing corners.
  • 2 These maximum fillet radii will be cleared by the bearing corners.
  • 3 Negative value indicates effective center inside cone backface.
  • 4 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values.
  • 5 Based on 1 x 106 revolutions L10 life, for the ISO life calculation method.
  • 6 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values for a single-row, C90(2) is the two-row radial value.
  • 7 These factors apply for both inch and metric calculations. Consult your Timken representative for instruction on use.
  • 8 These factors apply for both inch and metric calculations. Consult your Timken representative for instruction on use.
  • 9 These factors apply for both inch and metric calculations. Consult your Timken representative for instruction on use.
  • 10 Geometry constant for Lubrication Life Adjustment Factor a3l.