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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 78000

Cone Part Number

 N/A 78255X

Cup Part Number

 N/A 78551

Design Unit

 N/A Inch

Cage Material

 N/A Stamped Steel

Dimensions

d - Bore

 N/A 2.5586 in64.988 mm

D - Cup Outer Diameter

 N/A 5.5130 in140.030 mm

B - Cone Width

 N/A 1.2962 in32.923 mm

C - Cup Width

 N/A 0.9260 in23.520 mm

T - Bearing Width

 N/A 1.4375 in36.513 mm

Abutment and Fillet Dimensions

R - Cone Backface "To Clear" Radius1 N/A 0.14 in3.600 mm
r - Cup Backface "To Clear" Radius2 N/A 0.090 in2.29 mm

da - Cone Frontface Backing Diameter

 N/A 3.11 in79 mm

db - Cone Backface Backing Diameter

 N/A 3.5 in89 mm

Da - Cup Frontface Backing Diameter

 N/A 5.22 in132.59 mm

Db - Cup Backface Backing Diameter

 N/A 4.61 in117.09 mm

Ab - Cage-Cone Frontface Clearance

 N/A 0.22 in5.6 mm

Aa - Cage-Cone Backface Clearance

 N/A 0.24 in6.1 mm
a - Effective Center Location3 N/A 0.31 in7.9 mm

Basic Load Ratings

C90 - Dynamic Radial Rating (90 million revolutions)4 N/A 11800 lbf52600 N
C1 - Dynamic Radial Rating (1 million revolutions)5 N/A 45600 lbf203000 N

C0 - Static Radial Rating

 N/A 43400 lbf193000 N
Ca90 - Dynamic Thrust Rating (90 million revolutions)6 N/A 17500 lbf77900 N

Factors

K - Factor7 N/A 0.67
e - ISO Factor8 N/A 0.87
Y - ISO Factor9 N/A 0.69

G1 - Heat Generation Factor (Roller-Raceway)

 N/A 62.6

G2 - Heat Generation Factor (Rib-Roller End)

 N/A 19.1
Cg - Geometry Factor10 N/A 0.0884
  • 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.
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