Glossary of abbreviations and symbols


Bearing & gear dimensions
Symbol Feature Units
α Pressure angle of gear teeth °
b2 Face width of gear teeth in
Bi Size of hole in inner ring in
Bo Size of hole in outer ring in
D2 Pitch diameter of gear in
di Inside diameter of inner ring in
Di Internal diameter on outer ring in
Do Outside diameter of outer ring in
do External diameter on inner ring in
Dp Diameter of bearing raceway in
dr Internal diameter on inner ring in
Dr External diameter on outer ring in
Dw Diameter of rolling element in
FD Full depth involute spur gear
(ref. ANSI B6.1-1968, R1974 or ISO 53:1998)
FS Fellow stub involute spur gear
(ref. Machinery’s Handbook, 18th Edition)
H Height of overall bearing assembly in
Hi Height of inner ring in
Ho Height of outer ring in
Li Bolt circle in inner ring in
Lo Bolt circle in outer ring in
m Module of gear teeth = 25.4/Pd mm
nf Number of lubrication
nipples/fittings per plane
ni Number of holes in inner ring
no Number of holes in outer ring
Pd Diametral pitch
SD Stub involute spur gear
(ref. ASA B6.1-1932)
x2 Addendum modification coefficient of gear teeth
(“+” sign increase tooth thickness at D2
and “-” sign decreases tooth thickness at D2)
z2 Number of gear teeth
Bearing & gear properties
Symbol Feature Units
Crm Moment load rating ft-lbs
Fz Maximum allowable gear tooth load lbs
G Weight of bearing assembly lbs
Mw Friction torque of bearing,
installed and subjected to loads
Pinion dimensions
Symbol Feature Units
b1 Face width in
D1 Pitch diameter in
Di1 Stock bore in
Do1 Outside diamter in
Dr1 Diamter of hub in
L1 Length of pinion in
Pd Diametral pitch in
w Square key size, nominal in
x1 Addendum modification coefficient
z1 Number of teeth
Application data
Symbol Feature Units
fa Applicaiton Service Factor
Fa Force parallel to bearing axis of rotation lbs
Fr Force perpendicular to bearing axis of rotation lbs
Mk Tilting moment about bearing centerline ft-lbs
N Rotation speed rpm
μ Friction coefficient
Symbol Feature Units
ft Linear unit of measurement foot
ft-lbs Units of torque or moment foot-pounts
in Linear unit of measurement inch
lbs Units of force or weight pounds
mm Linear unit of measurement (SI) millimeter
AGMA American Gear Manufacturers Association
ANSI American National Standards Institute
ASTM American Society for Testing and Materials
DIN Deutsches Institute für Normung
ISO International Standards Organization
NLGI National Lubricating Grease Institute
SAE Society of Automative Engineers