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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 78000C

Cone Part Number

 N/A 78250AC

Design Units

 N/A Imperial

Cage Type

 N/A Stamped Steel
C1 - Dynamic Radial Rating (Two-Row, 1 million revolutions)1 N/A 92600 lbf412000 N
C90(2) - Dynamic Radial Rating (Two-Row, 90 million revolutions)2 N/A 24000 lbf107000 N

Dimensions

d - Cone Bore

 N/A 2 1/2 in63.500 mm

B - Cone Width

 N/A 1.3085 in33.236 mm

Abutment and Fillet Dimensions

R - Cone Backface "To Clear" Radius3 N/A 0.2 in5.1 mm

da - Cone Frontface Backing Diameter

 N/A 3.05 in77.5 mm

db - Cone Backface Backing Diameter

 N/A 3.66 in93 mm

Ab - Cage-Cone Frontface Clearance

 N/A 0.21 in5.3 mm

Aa - Cage-Cone Backface Clearance

 N/A 0.22 in5.6 mm
a - Effective Center Location4 N/A 0.33 in8.4 mm

Basic Load Ratings

C90 - Dynamic Radial Rating (90 million revolutions)5 N/A 13800 lbf61300 N
C1 - Dynamic Radial Rating (1 million revolutions)6 N/A 53200 lbf237000 N

C0 - Static Radial Rating

 N/A 52600 lbf234000 N
Ca90 - Dynamic Thrust Rating (90 million revolutions)7 N/A 20400 lbf90900 N

Factors

K - Factor8 N/A 0.67

G1 - Heat Generation Factor (Roller-Raceway)

 N/A 71.3

G2 - Heat Generation Factor (Rib-Roller End)

 N/A 17.6
Cg - Geometry Factor9 N/A 0.0926
  • 1 Based on 1 x 106 revolutions L10 life, for the ISO life calculation method.
  • 2 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.
  • 3 These maximum fillet radii will be cleared by the bearing corners.
  • 4 Negative value indicates effective center inside cone backface.
  • 5 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values.
  • 6 Based on 1 x 106 revolutions L10 life, for the ISO life calculation method.
  • 7 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.
  • 8 These factors apply for both inch and metric calculations. Consult your Timken representative for instruction on use.
  • 9 Geometry constant for Lubrication Life Adjustment Factor a3l.
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