The Timken Company
The Timken Company
4500 Mt Pleasant St. NW
N. Canton, OH 44720
Phone: (234) 262-3000
E-Mail: CustomerCAD@timken.com • Web site: www.timken.com
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Unit of Measure

Specifications

Cone Part Number

 N/A NA78250

Cup Part Number

 N/A 78549D

Related Assembly Number(s)

 N/A NA78250-90032

Design Unit

 N/A Inch

Dimensions

d - Bore

 N/A 2 1/2 in63.500 mm

D - Cup Outer Diameter

 N/A 5.5000 in139.700 mm

T - Bearing Width across Cones

 N/A 3.0625 in77.788 mm

C - Double Cup Width

 N/A 2.0395 in51.803 mm

Abutment and Fillet Dimensions

R - Cone Backface "To Clear" Radius1 N/A 0.09 in2.300 mm
r - Cup Backface "To Clear" Radius2 N/A 0.06 in1.5 mm

db - Cone Backface Backing Diameter

 N/A 3.35 in85 mm

Da - Cup Frontface Backing Diameter

 N/A 5.19 in131.83 mm

Basic Load Ratings

C90 - Dynamic Radial Rating (90 million revolutions)3 N/A 11800 lbf52600 N
C1 - Dynamic Radial Rating (1 million revolutions)4 N/A 79300 lbf353000 N
Ca90 - Dynamic Thrust Rating (90 million revolutions)5 N/A 17500 lbf77900 N
C90(2) - Dynamic Radial Rating (Two-Row, 90 million revolutions)6 N/A 20600 lbf91500 N

Factors

K - Factor7 N/A 0.67
e - ISO Factor8 N/A 0.87
Y1 - ISO Factor9 N/A 0.78
Y2 - ISO Factor10 N/A 1.16
  • 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 Based on 90 x 106 revolutions L10 life, for The Timken Company life calculation method. C90 and Ca90 are radial and thrust values.
  • 4 Based on 1 x 106 revolutions L10 life, for the ISO life calculation method.
  • 5 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.
  • 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 These factors apply for both inch and metric calculations. Consult your Timken representative for instruction on use.