Symbols For Gear Calculations

 
The following is a list of the gear symbols that we will use on this site for calculations. You can also download and print this reference sheet to keep with you. (PDF)
 
 

k

A Variable

 

P

Features On A Pinion

 

Profile Variation

Fe

Active Face Width

 

W

Features On A Worm

 

Q

Quality Number

a

Addendum

 

rf

Fillet Radius (when constant)

 

Vr

Radial Runout

a

Addendum Angle

 

mG

Gear Ratio

 

VrT

Radial Runout Tolerance

VpA

Allowable Pitch Variation

 

Ψ

Helix / Spiral Angle

 

D

Pitch Diameter

A

Allowable Variation

 

Vx

Index Variation

 

ΓR

Root Angle

ӨN

Angular Pitch

 

DI

Internal Diameter

 

DR

Root Diameter

Qt

Arc of Action

 

Ө

Involute Polar Angle

 

Σ

Shaft Angle

Qa

Arc Of Approach

 

ε

Involute Roll Angle

 

Vs

Spacing Variation

Qr

Arc Of Recess

 

L

Lead

 

Rr

Test Radius

PX

Axial Base Pitch

 

λ

Lead Angle

 

Dt

Throat Diameter

Px

Axial Pitch

 

Z

Length Of Action

 

rt

Throat Form Radius

Φx

Axial Pressure Angle

 

mo

Modified Contact Ratio

 

rr

Tip Or Edge Radius Of Tool

tx

Axial Thickness

 

m

Module

 

T

Tolerances

B

Backlash

 

PN

Normal Base Pitch

 

VΨT

Tooth Alignment Tolerance

tb

Base Circular Thickness

 

anc

Normal Chordal Addendum

 

Tooth Alignment Variation

Db

Base Diameter

 

tnc

Normal Chordal Thickness

 

tr

Tooth Thickness Tolerance

Ψb

Base Helix Angle

 

Pn

Normal Circular Pitch

 

VqT

Tooth-to-Tooth Composite Tolerance (double flank)

λb

Base Lead Angle

 

tn

Normal Circular Thickness

 

Vq

Tooth-to-Tooth Composite Variation (double flank)

Pb

Base Pitch

 

Pnd

Normal Diametral Pitch

 

Vap

Total Accumulated Pitch Variation

C

Center Distance

 

mn

Normal Module

 

Vapk

Total Accumulated Pitch Variation within a sector  of K Pitches

ac

Chordal Addendum

 

Vpn

Normal Pitch Variation

 

Vcqt

Total Composite Tolerances (double flank)

tc

Chordal Thickness

 

n

Normal Plane

 

Vcq

Total Composite Variation (double flank)

P

Circular Pitch

 

Φn

Normal Pressure Angle

 

mt

Total Contact Ratio

t

Circular Tooth Thickness

 

N

Number Of Teeth Or Threads

 

Ft

Total Face Width

c

Clearance

 

dp

Operating Pitch Diameter

 

Pt

Transverse Circular Pitch

mc

Contact Ratio

 

DO

Outside Diameter

 

tt

Transverse Circular Thickness

DC

Datum Circle

 

λo

Outside Lead Angle

 

mp

Transverse Contact Ratio

b

Dedendum

 

Γ

Pitch Angle

 

tp

Transverse Plane

Pd

Diametral Pitch

 

λp

Pitch Lead Angle

 

Φt

Transverse Pressure Angle

Ne

Equivalent Number Of Teeth

 

Vp

Pitch Variation

 

Pm

True Position Pitch

mF

Face Contact Ratio

 

Φ

Pressure Angle

 

ht

Whole Depth

F

Face Width

 

p

Profile Radius Of Curvature

 

hk

Working Depth

G

Features Of A Gear

 

VΦT

Profile Tolerance