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Title1012-G05 Gear Nomenclature, Definition of Terms
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ANSI/AGMA 1012-G05
[Revision of

ANSI/AGMA 1012--F90]

AMERICAN NATIONAL STANDARD

Gear Nomenclature, Definition of Terms
with Symbols

Page 2

ii

Gear Nomenclature, Definitions of Terms with Symbols
ANSI/AGMA 1012--G05
[Revision of ANSI/AGMA 1012--F90]

Approval of an American National Standard requires verification by ANSI that the require-
ments for due process, consensus, and other criteria for approval have been met by the
standards developer.

Consensus is established when, in the judgment of the ANSI Board of Standards Review,
substantial agreement has been reached by directly and materially affected interests.
Substantial agreement means much more than a simple majority, but not necessarily una-
nimity. Consensus requires that all views and objections be considered, and that a
concerted effort be made toward their resolution.

The use of American National Standards is completely voluntary; their existence does not
in any respect preclude anyone, whether he has approved the standards or not, from
manufacturing, marketing, purchasing, or using products, processes, or procedures not
conforming to the standards.

The American National Standards Institute does not develop standards and will in no
circumstances give an interpretation of any American National Standard. Moreover, no
person shall have the right or authority to issue an interpretation of an American National
Standard in the name of the American National Standards Institute. Requests for interpre-
tation of this standard should be addressed to the American Gear Manufacturers
Association.

CAUTION NOTICE: AGMA technical publications are subject to constant improvement,
revision, or withdrawal as dictated by experience. Any person who refers to any AGMA
technical publication should be sure that the publication is the latest available from the
Association on the subject matter.

[Tables or other self--supporting sections may be referenced. Citations should read: See
ANSI/AGMA 1012--G05, Gear Nomenclature, Definitions of Terms with Symbols, pub-
lished by the American Gear Manufacturers Association, 500 Montgomery Street, Suite
350, Alexandria, Virginia 22314, http://www.agma.org.]

Approved September 29, 2005

ABSTRACT

This standard lists terms and their definitions with symbols for gear nomenclature.

Published by

American Gear Manufacturers Association
500 Montgomery Street, Suite 350, Alexandria, Virginia 22314

Copyright 2005 by American Gear Manufacturers Association
All rights reserved.

No part of this publication may be reproduced in any form, in an electronic
retrieval system or otherwise, without prior written permission of the publisher.

Printed in the United States of America

ISBN: 1--55589--846--7

American
National
Standard

Page 40

ANSI/AGMA 1012--G05 AMERICAN NATIONAL STANDARD

34 AGMA 2005 ---- All rights reserved

Distinction is made as to the direction and algebraic
sign of this reading. A condition wherein the actual
tooth flank position was nearer to the datum tooth
flank, in the specified measuring path direction
(clockwise or counterclockwise), than the theoretical
position would be considered a minus (--) deviation.
A condition wherein the actual tooth flank position
was farther from the datum tooth flank, in the
specified measuring path direction, than the theoret-
ical position would be considered a plus (+) devi-
ation. (ANSI/AGMA 2015--1--A01)

ANSI/AGMA 2015--1--A01 specifies direction of
tolerancing for index deviation to be along the arc of
the tolerance diameter circle within the transverse
plane.

5.4.2 Cumulative pitch deviation, total, Fp

The largest algebraic difference between the index
deviation values for a specified flank. (ANSI/AGMA
2015--1--A01)

Distinction is not made as to the direction or
algebraic sign of this reading.

ANSI/AGMA 2015--1--A01 specifies direction of
tolerancing for total cumulative pitch deviation to be
along the arc of the tolerance diameter circle within
the transverse plane.

5.4.3 Spacing

The term spacing is used as a general term to
reference the accuracy with which teeth are posi-
tioned around the gear. Spacing has no numerical
value and refers only to a group of numerically
valued tooth position measurements such as pitch or
index.

5.4.4 Spacing variation, Vs

Spacing variation is the difference between any two
(2) adjacent measurements of pitch as obtained by a
two probe device, see figure 98, or is equal to the
difference between two (2) adjacent pitch variation
values obtained from a single probe device.

5.5 Pitch of teeth

5.5.1 Pitch range

Pitch range is the difference between the longest
and the shortest pitches on a gear.

5.5.2 True position pitch, pm

True position pitch is the circumference of the datum
circle divided by the number of teeth. This can be
determined by the average of all pitch measure-
ments of the entire gear taken on successive pairs of

teeth, or between corresponding points of adjacent
teeth generated by an angular positioning device.

Datum
circle

Figure 98 -- Schematic of pitch measurement,
two probe device

5.5.3 Pitch variation, Vp

Pitch variation is the algebraic plus or minus (+ or --)
difference in the transverse plane, between the true
position pitch and an actual pitch measurement. If
pitch is measured in a plane other than the trans-
verse plane, a correction using the appropriate helix
angle must be applied to the measured value, see
figures 99 and 100.

Dashed lines represent
theoretical location

--Vp

True
position

pitch

Circular
pitch, p

+Vp

Figure 99 -- Pitch variation (plus and minus)

5.5.4 Allowable pitch variation, VpA

Allowable pitch variation is the maximum allowable
amount of pitch variation. It is the permissible plus or
minus variation from the true position pitch and it is
the amount shown in the tolerance tables or formulas
of AGMA 2000--A88.

5.5.5 Normal pitch variation, Vpn

Normal pitch variation is the plus or minus pitch
measured in the normal plane.

Page 41

ANSI/AGMA 1012--G05AMERICAN NATIONAL STANDARD

35AGMA 2005 ---- All rights reserved

Sector of three pitches

+Vp

Vap
--Vp

Tooth number

In
d
e
x

va
ri
a
tio

n
,

V
x

+

0

--

1 2 3 4 5 6 7 8 9 10

Vap3

Figure 100 -- Accumulated pitch variation

5.5.6 Total accumulated pitch variation, Vap

Total accumulated pitch variation is equal to the
algebraic difference between the maximum and
minimum values obtained from the summation of
successive values of pitch variation and is the same
as total index variation, see figure 100.

5.5.7 Total accumulated pitch variation
tolerance

Total accumulated pitch variation tolerance is the
permissible amount of total accumulated pitch
variation.

5.5.8 Total accumulated pitch variation, within a
sector of k pitches, Vapk

Total accumulated pitch variation, within a sector of k
pitches is equal to the algebraic sum of individual
plus or minus adjacent pitch variations within that
sector. The total accumulated pitch variation within a
Sector of three (k = 3) pitches is shown in figure 100.

5.5.9 Single pitch deviation, fpt

The displacement of any tooth flank from its theoreti-
cal position relative to the corresponding flank of an
adjacent tooth, see figure 97. (ANSI/AGMA
2015--1--A01)

Distinction is made as to the algebraic sign of this
reading. Thus, a condition wherein the actual tooth
flank position was nearer to the adjacent tooth flank
than the theoretical position would be considered a
minus (--) deviation. A condition wherein the actual
tooth flank position was farther from the adjacent
tooth flank than the theoretical position would be
considered a plus (+) deviation.

ANSI/AGMA 2015--1--A01 specifies tolerancing di-
rection of measurement for single pitch deviation to

be along the arc of the tolerance diameter circle
within the transverse plane.

5.6 Runout of teeth

5.6.1 Runout

Runout is the maximum variation of the distance
between a surface of revolution and a datum
surface, measured perpendicular to that datum
surface.

5.6.2 Axial runout (wobble)

Axial runout (wobble) is the runout of the teeth
measured in a direction parallel to the datum axis of
rotation.

5.6.3 Radial runout, Vr

Radial runout is the runout measured in a direction
perpendicular to the datum axis of rotation.

5.6.4 Radial runout tolerance, VrT

Radial runout tolerance is the permissible amount of
radial runout.

5.6.5 Indicating over pins

Indicating over pins is the measurement of the
change in radial distance over pins or wires placed in
each tooth space to determine runout with reference
to the rotating axis.

5.7 Profile of teeth

5.7.1 Functional profile

That portion of the tooth flank between the profile
control diameter and the start of tip break, see figure
101.

Functional
profile

Functional
profile

External
tooth

Internal
tooth Base circle

Addendum (inside)
diameter

Start of tip break

Pitch diameter

Profile control
diameter

Root diameter

Root diameter
Base circle

Profile control
diameter

Pitch diameter
Start of tip break

Addendum (outside)
diameter

Figure 101 -- Functional profile

Page 80

PUBLISHED BY
AMERICAN GEAR MANUFACTURERS ASSOCIATION

500 MONTGOMERY STREET, SUITE 350, ALEXANDRIA, VIRGINIA 22314

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