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 31318M

Cone Part Number

 N/A X31318M

Cup Part Number

 N/A Y31318M

Design Unit

 N/A Metric

Cage Material

 N/A Stamped Steel

Dimensions

d - Bore

 N/A 90 mm3.5433 in

D - Cup Outer Diameter

 N/A 190 mm7.4803 in

B - Cone Width

 N/A 43 mm1.6929 in

C - Cup Width

 N/A 30.000 mm1.1811 in

T - Bearing Width

 N/A 46.5 mm1.8307 in

Abutment and Fillet Dimensions

R - Cone Backface "To Clear" Radius1 N/A 4.060 mm0.16 in
r - Cup Backface "To Clear" Radius2 N/A 3.05 mm0.12 in

da - Cone Frontface Backing Diameter

 N/A 117 mm4.61 in

db - Cone Backface Backing Diameter

 N/A 128 mm5.04 in

Da - Cup Frontface Backing Diameter

 N/A 182.12 mm7.17 in

Db - Cup Backface Backing Diameter

 N/A 164.08 mm6.46 in

Ab - Cage-Cone Frontface Clearance

 N/A 6.6 mm0.26 in

Aa - Cage-Cone Backface Clearance

 N/A 6.9 mm0.27 in
a - Effective Center Location3 N/A 13.2 mm0.52 in

Basic Load Ratings

C90 - Dynamic Radial Rating (90 million revolutions)4 N/A 84000 N18900 lbf
C1 - Dynamic Radial Rating (1 million revolutions)5 N/A 324000 N72800 lbf

C0 - Static Radial Rating

 N/A 421000 N94600 lbf
Ca90 - Dynamic Thrust Rating (90 million revolutions)6 N/A 119000 N26700 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 169.3

G2 - Heat Generation Factor (Rib-Roller End)

 N/A 37.1
Cg - Geometry Factor10 N/A 0.114
  • 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.