BS 919-3:2007

BRITISH STANDARD

Screw gauge limits and

tolerances –
Part 3: Specification for gauges for
screw threads of ISO metric form
ICS 21.040.10

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Publishing and copyright information

The BSI copyright notice displayed in this document indicates when the
document was last issued.

© BSI 2007

ISBN 978 0 580 57935 6

The following BSI references relate to the work on this standard:

Committee reference TDW/4
Draft for comment 07/30158517 DC

Publication history
First published December 1968
Second edition, October 2007

Amendments issued since publication

Amd. no. Date Text affected

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Contents
Foreword iii
1 Scope 1
2 Normative references 1
3 Terms and definitions and symbols 1
4 General design features and tolerances of gauges 2
5 Marking 4
Annexes
Annex A (informative) Function and method of use of various
gauge types 27
Annex B (informative) Inspection procedures and the settlement
of disputes 31
Annex C (informative) Reference temperature 32
Annex D (informative) Hardness 32
Bibliography 33
List of figures
Figure 0 – “Blunt start” at end of thread on gauge 5
Figure 1 – Thread profiles for screw plug, ring and calliper gauges
having complete flanks 6
Figure 2 – Thread profiles for screw plug, ring and calliper threads of
truncated form 8
Figure 3 – Alternative form of GO calliper gauge anvil for product
threads having pitches finer than 0.5 mm 10
Figure 4 – Alternative form of NOT GO calliper gauge anvil for product
threads having pitches finer than 1.0 mm 10
Figure 5 – Effective diameter tolerance zones of gauges for external
product threads having pitch diameter tolerances above 80 μm and
up to 125 μm 12
Figure 6 – Effective diameter tolerance zones of gauges for external
product threads having pitch diameter tolerances above 200 μm and
up to 315 μm 13
Figure 7 – Effective diameter tolerance zones of gauges for internal
product threads having pitch diameter tolerances above 80 μm and
up to 125 μm 14
Figure 8 – Effective diameter tolerance zones of gauges for internal
product threads having pitch diameter tolerances above 200 μm and
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up to 315 μm 15
List of tables
Table 1 – Dimensions of root clearances of GO screw gauges
(see Figure 1) 7
Table 2 – Dimensions of root clearances of NOT GO screw gauges
(see Figure 2) 9
Table 3 – Flank angle tolerances 11
Table 4 – Pitch tolerances 11
Table 5 – External product thread deviations for effective diameters
of GO screw limit gauges and their associated check plugs and
setting plugs 16
Table 6 – External product thread deviations for effective diameters of
NOT GO screw limit gauges and their associated check plugs and
setting plugs 16

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Table 7 – External product thread deviations for effective diameters of

NOT GO screw limit gauges and their associated check plugs and
setting plugs 17
Table 8 – Deviations for minor diameters of new GO and NOT GO
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screw ring gauges, major diameters of new GO and NOT GO screw

plug gauges, and plain check plugs for new screw ring gauges 18
Table 9 – Deviations for major diameters of screw check plugs and
setting plugs for GO screw ring and calliper gauges 19
Table 10 – Deviations for major diameters of screw check plugs and
setting plugs for NOT GO screw ring and calliper gauges 20
Table 11 – External product thread deviations and allowable wear for
GO and NOT GO plain calliper and ring gauges 20
Table 12 – Internal product thread deviations and allowable wear for
GO and NOT GO plain plug gauges 21
Table 13 – External product thread information for calculation of
limits for new solid GO screw ring gauges and their associated
check plugs 22
Table 14 – External product thread information for calculation of limits
for adjustable GO screw ring and calliper gauges and their associated
setting plugs 23
Table 15 – External product thread information for calculation of limits
for new solid NOT GO screw ring gauges and their associated check
plugs 24
Table 16 – External product thread information for calculation of limits
for adjustable NOT GO screw ring and calliper gauges and their
associated setting plugs 25
Table 17 – Internal product thread information for calculation of limits
for GO and NOT GO screw plug gauges 26

Summary of pages
This document comprises a front cover, an inside front cover,
pages i to iii, a blank page, pages 1 to 33 and a back cover.

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 BS 919-3:2007

Foreword
This British Standard is published by BSI and came into effect
on 31 October 2007. It was prepared by Subcommittee SFTSE/1,
Screws and fasteners technical specification committee, under the
authority of Technical Committee TDW/4, Technical product
realization. A list of organizations represented on these committees
can be obtained on request to their secretaries.
BS 919, Screw gauge limits and tolerances is in four parts:
Part 1: Specification for gauges for screw threads of unified
form
Part 2: Specification for gauges for screw threads of Whitworth
and B.A. forms
Part 3: Specification for gauges for screw threads of ISO metric
form
Part 4: Limits of size for gauges for screw threads of unified
form diameters ---14 in and larger

Supersession
This Part of BS 919 supersedes BS 919-3:1968, which is withdrawn.
NOTE Attention is drawn to the fact that, for reasons of economy, this
standard provides for wear limits for some GO gauges which are outside
those of the product thread.

Relationship with other publications

This British Standard is intended for use with BS 3643, which specifies
the corresponding screw threads.

Information about this document

This British Standard has been fully revised to bring it up to date.

Presentational conventions
The provisions of this standard are presented in roman (i.e. upright)
type. Its requirements are expressed in sentences in which the principal
auxiliary verb is “shall”.
Commentary, explanation and general informative material is --`,,```,,,,````-`-`,,`,,`,`,,`---

presented in notes in smaller italic type, and does not constitute a

normative element.

Contractual and legal considerations

This publication does not purport to include all the necessary provisions
of a contract. Users are responsible for its correct application.
Compliance with a British Standard cannot confer immunity
from legal obligations.

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 BS 919-3:2007

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1 Scope
This Part of BS 919 specifies requirements for the following types
of gauges for checking ISO metric screw threads of nominal
diameter 1 mm and larger made in accordance with BS 3643.
a) Screw gauges:
1) GO and NOT GO screw plug gauges;
2) GO and NOT GO screw ring gauges, solid type;
3) GO and NOT GO screw ring gauges, adjustable type;
4) GO and NOT GO screw calliper gauges, adjustable type.
b) GO and NOT GO plain plug gauges and GO and NOT GO calliper and
ring gauges for the crest diameters of product threads.
c) Setting plugs for GO and NOT GO adjustable screw ring gauges and
for GO and NOT GO screw calliper gauges:
1) double length;
2) single length.
d) GO and NOT GO check plug gauges for solid type GO and NOT GO
screw ring gauges.
e) NOT GO wear check plug gauges for solid type GO and NOT GO
screw ring gauges.
Annex A provides guidance on the functions and methods of use of the
various types of gauges and Annex B recommends a procedure for the
settlement of disputes arising when borderline products are inspected.
Guidance on the hardness of gauges is given in Annex C, and Annex D
provides information on the reference temperature.

2 Normative references
The following referenced documents are indispensable for the
application of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the
referenced document (including any amendments) applies.
BS 1044-1:1964, Specification for gauge blanks – Part 1: Plug, ring
and calliper gauges

3 Terms and definitions and symbols

3.1 Terms and definitions
For the purposes of this part of BS 919, the terms and definitions given
in BS 6528:1984 and the following apply.

3.1.1 basic profile

theoretical profile of a screw thread in an axial plane defined by
theoretical dimensions and angles common to internal and external
threads
NOTE This definition is repeated from BS 6528:1984 for the convenience
of users of this standard.

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3.1 Symbols
For the purposes of this part of BS 919, the following symbols apply.
b maximum width of clearance groove
D basic major diameter of internal thread (nominal diameter)
D1 basic minor diameter of internal thread
D2 basic pitch diameter of internal thread
d basic major diameter of external thread (nominal diameter)
d1 basic minor diameter of external thread
d2 basic pitch diameter of external thread
d3 minor diameter of external thread
H height of fundamental triangle
P pitch

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r root radius of external thread
T tolerance
TD1 tolerance for D1
TD2 tolerance for D2
Td1 tolerance for d1
Td2 tolerance for d2

4 General design features and

tolerances of gauges
4.1 Dimensions of gauges
The general dimensions of gauges shall conform to BS 1044-1, subject
to any special requirements in 4.2 to 4.7. For normal purposes, the
length of thread shall be determined by the length of the gauge blank.

4.2 Thread profiles of screw gauges

NOTE The various types of screw gauges have full flank or truncated
thread profiles.
Nominal full flank profiles for screw plug, ring and calliper gauges shall
be as shown in Figure 1a) and Figure 1b). The corresponding truncated
thread profiles shall be as shown in Figure 2a) and Figure 2b).
The maximum widths b1 and b2 of the clearance grooves shall be as
shown on the full flank profiles in Figure 1a) and Figure 1b) and
specified in Table 1. No clearance grooves need be provided on full
flank profiles provided the flanks are continued to clear width b1 or b2
as appropriate, but the root shall be radiused as shown. Maximum
values for r1 and r2 shall be as specified in Table 1. For fine pitches
(below 1.25 mm on ring gauges and 0.6 mm on plug gauges) it is not
practicable to provide separate clearance grooves.

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The forms of the clearance grooves and crest truncations on gauges

with truncated profiles shall be as shown in Figure 2a) and Figure 2b).
F1, F2 and b3 shall be as specified in Table 2. The form of root clearance
is optional but it may not be displaced in relation to the centre of the
profile by more than S = 0.05P (see Note to Table 2).
Alternative forms of GO and NOT GO calliper gauge anvils for product
threads having fine pitches shall be as shown in Figure 3 and Figure 4,
respectively.

4.3 Flank angle and pitch tolerances on screw

gauges
The flank angle tolerances for gauges having full flank threads and
truncated threads respectively shall be as specified in Table 3.
The pitch tolerances for gauges shall be as specified in Table 4.

4.4 Disposition of effective diameter tolerance

zones of gauges
The positions of the effective diameter tolerance zones of the GO and
NOT GO screw gauges, setting plugs and various check plugs shall be

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as shown in relation to the effective diameter limits of the product
threads in Figure 5 to Figure 8.

4.5 Diametral tolerances on screw gauges

Limits of tolerance (upper and lower deviations) for the effective
diameters of the various types of gauges shall be as specified
in Table 5 to Table 7.
Limits of tolerance for the crest diameters of the various types of gauges
shall be as specified in Table 8 to Table 10.

4.6 Tolerances on plain gauges

4.6.1 Limits of tolerance (upper and lower deviations) for GO and
NOT GO plain calliper and ring gauges shall be as specified in Table 11
and, for GO and NOT GO plain plug gauges, as specified in Table 12.
4.6.2 Limits of tolerance for GO and NOT GO plain check plugs for the
minor diameters of solid GO and NOT GO screw ring gauges shall be as
specified in Table 8. These tolerances shall be applied to the
appropriate deviations for the minor diameter of the screw ring gauge.

4.7 Determination of gauge limits

The screw gauge limits can be calculated using the information
summarized in Table 13 to Table 17 inclusive.

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4.8 Feather edges

To avoid feather edges on screw plug and ring gauges and setting plugs,
the partial thread at both ends of the gauge shall be removed to a blunt
start (see Figure 0), except for:
a) screw plug gauges and setting plugs in sizes below 4 mm and/or
with external core centres;
b) screw ring gauges of 12 mm nominal size and smaller or with
pitches of 1.25 mm and finer, and all screw plug gauges and
setting plugs with pitches of 1 mm and finer for which
a 60° chamfer from the axis of the gauge is permitted in lieu of the
removal of the partial thread.
Not more than one complete turn of the thread shall be removed to the
point where the full thread form is obtained.
On double length setting plugs with pitches of 1 mm and coarser, the
feather edge shall be completely removed where the truncated portion
meets the full form portion.

4.9 Dirt clearance grooves

When specified by the purchaser, a screw plug gauge shall have a dirt
clearance groove cut axially to the thread to a depth slightly below the
root of the thread. This groove shall be cut at the position where the
thread commences its full section as described in 4.8.

4.10 Removal of sharp edges

All sharp edges on the gauging portions and handles shall be removed.

5 Marking
Each gauge shall be plainly and permanently marked with the minimum
marking essential for positive identification.
Unless otherwise specified by the purchaser, each gauge shall be
marked with the following particulars:
a) the designation of the corresponding product thread in accordance
with BS 3643;
NOTE In the case of left-hand screw gauges, the symbol L.H. follows
the designation.
b) the size of the gauge, i.e. the limiting size of the product thread
which the gauge is intended to control;
c) ‘‘GO’’ or ‘‘NOT GO’’, as applicable;
d) ‘‘SET’’, in the case of setting plugs for adjustable screw ring or
calliper gauges;
e) ‘‘CHECK’’, in the case of check plugs for solid screw rings or
calliper gauges;
f) the manufacturer’s name or trade mark;
g) a serial number if required for recording purposes.

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The marking of plug gauges of the renewable end type shall, where
practicable, appear on the face of the gauging member in addition to the
handle.

Examples of marking for gauges

Class of gauge Marking
GO screw plug M8 × 1–6H, GO 7.350, X Co. No. 35
NOT GO screw plug M8 × 1–6H, NOT GO 7.500, X Co. No. 3
Plain plugs for minor diameter M8 × 1–6H, GO 6.917, X Co. No. 9
M8 × 1–6H, NOT GO 7.153, X Co. No. 15
GO screw ring or calliper M10 × 1.5–6g, GO 8.994, X Co. No. 56
NOT GO screw ring or calliper M10 × 1.5–6g, NOT GO 8.862, X Co. No. 75
Plain callipers for major diameter M10 × 1.5–6g, GO 9.968, X Co. No. 43
M10 × 1.5–6g, NOT GO 9.732, X Co. No. 64
GO setting plug M10 × 1.5–6g, GO SET 8.994, X Co. No. 24
NOT GO check plug M10 × 1.5–6g, NOT GO CHECK 8.862, X Co. No. 97

Figure 0 “Blunt start” at end of thread on gauge

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BS 919-3:2007
Figure 1 Thread profiles for screw plug, ring and calliper gauges having complete flanks

r2
P
30 P/2 H/12
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P/8
H/4 D1
Pitch line H/6
of gauge Major Clearing diameter.
diameter Maximum size.
b2
b2 Effective diameter
Root cleared above this line.
Form of clearance optional.
a) Full flank thread on GO plug gauge (Form of clearance for pitches below 0.6 mm; optional for coarser pitches. r2 = 0.144P; clearing diameter max = D1 – 0.144P)
Not for Resale

Root cleared above this line.

b1 Form of clearance optional.
H/12
H/8
Pitch line
of gauge r1
30 P/2 b1 d
Clearing H/24
Effective diameter.
P/4 diameter minimum
P size
Minor
diameter
b) Full flank thread on GO ring or calliper gauge (Form of clearance for pitches below 1.25 mm; optional for coarser pitches. r1 = 0.072P;
clearing diameter max = d + 0.072P)
 BS 919-3:2007

Table 1 Dimensions of root clearances of GO screw gauges

(see Figure 1)
unit = mm
1 2 3 4 5

b1 r1 b2 r2
Pitch (P) max. max. max. max.
(0.125P) (0.072P) (0.25P) (0.144P)
0.2 A) 0.014 B) 0.029
0.25 A) 0.018 B) 0.036
0.3 A) 0.022 B) 0.043

0.35 A) 0.025 B) 0.050

0.4 A) 0.029 B) 0.058
0.45 A) 0.032 B) 0.065

0.5 A) 0.036 B) 0.072

0.6 A) 0.043 0.15 0.086
0.7 A) 0.050 0.18 0.10
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0.75 A) 0.054 0.19 0.11

0.8 A) 0.058 0.20 0.12
1.0 A) 0.072 0.25 0.14

1.25 0.16 0.09 0.31 0.18

1.5 0.19 0.11 0.38 0.22
1.75 0.22 0.13 0.44 0.25

2.0 0.25 0.14 0.50 0.29

2.5 0.31 0.18 0.61 0.36
3.0 0.38 0.22 0.75 0.43

3.5 0.44 0.25 0.88 0.50

4.0 0.5 0.29 1.0 0.58
4.5 0.55 0.32 1.1 0.65

5.0 0.6 0.36 1.25 0.72

5.5 0.7 0.40 1.4 0.79
6.0 0.8 0.43 1.5 0.86
A) Without clearance groove. The flanks have to be continued to clear width b1 [see Figure 1b)] and the root has to be
radiused (r1 max., see Column 3).
B) Without clearance groove. The flanks have to be continued to clear width b2 [see Figure 1a)] and the root has to be
radiused (r2 max., see Column 5).

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BS 919-3:2007
Figure 2 Thread profiles for screw plug, ring and calliper threads of truncated form
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30 P
F1
P/2
b3

F2 Major
diameter
Effective
b3 D
diameter 1min
Form of
dmin clearance
Form of
clearance optional of pitches
below 1.25 mm.
a) Truncated thread on NOT GO plug gauge
Not for Resale

b3 Form of clearance optional

F1
F2
b3
30
P/2
Effective
P diameter
d max Dmax
Minor Form of clearance
Pitch line diameter for pitches below
of gauge 1.25 mm.
b) Truncated thread on NOT GO ring or calliper gauge
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Table 2 Dimensions of root clearances of NOT GO screw gauges (see Figure 2)

unit = mm
1 2 3 4 5 6 7

Pitch (P) F1 (0.1P) F2 b2

0.2P 0.15P 0.1P Nominal size Deviation (±)

0.2 0.02
0.25 0.025
0.3 0.03
0.35 0.035
0.4 0.04
0.45 0.045
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0.5 0.05
0.6 0.06
0.7 0.07
0.75 0.075
Not for Resale

0.8 0.08
1 0.10
1.25 0.125 0.25 0.3 0.04
1.5 0.15 0.3 0.4 0.04
1.75 0.175 0.35 0.45 0.05
2 0.2 0.4 0.5 0.05
2.5 0.25 0.375 0.8 0.05
3 0.3 0.45 1.0 0.08
3.5 0.35 0.525 1.1 0.08
4 0.4 0.6 1.3 0.1
4.5 0.45 0.45 1.7 0.1

BS 919-3:2007
© BSI 2007 •

5 0.5 0.5 1.9 0.1

5.5 0.55 0.55 2.1 0.1
6 0.6 0.6 2.3 0.1
NOTE The form of clearance b2 is optional: the clearance may be displaced in relation to the centre of the profile of the thread by an amount S which is equal to the
permissible deviation of b2 (Table 2, Column 7). The deviation for b2 can be increased if the actual displacement is smaller than S by an amount which is double the
difference between the actual displacement and S.
9
 BS 919-3:2007

Figure 3 Alternative form of GO calliper gauge anvil for product threads

having pitches finer than 0.5 mm

GO calliper gauge
anvil

Product thread

Figure 4 Alternative form of NOT GO calliper gauge anvil for product

threads having pitches finer than 1.0 mm

NOT GO calliper
gauge anvil

Product thread
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Table 3 Flank angle tolerances

1 2 3
Pitch (P) Flank angle tolerances
mm Gauges with full form profiles. Figure 1 minutes ± Gauges with truncated profiles. Figure 2 minutes ±
0.2 60 60
0.25 48 48
0.3 40 40
0.35 35 35
0.4 31 31
0.45 26 26
0.5 25 25
0.6 21 21
0.7 18 18
0.75 17 17
0.8 16 16
1 16 16
1.25 13 16
1.5 12 16
1.75 11 16
Not for Resale

2 10 14
2.5 10 14
3 9 13
3.5 9 12
4 8 11
4.5 8 11
5 8 11
5.5 8 10
6 8 10

Table 4 Pitch tolerances

Unit = mm × 0.001 (μm)
© BSI 2007

1 2 3

BS 919-3:2007
Thread lengths up to 32 mm Thread lengths over 32 mm up to 50 mm Thread lengths over 50 mm up to 80 mm
5 6 7
NOTE The pitch tolerances are the maximum permissible errors between any two threads irrespective of sign except in the case of a double length setting plug, where the
•

thread length used when determining the pitch tolerance is one-half the overall thread length of the setting plug, and the pitch tolerance is the maximum permissible
error between any two threads spaced apart by not more than one-half the overall thread length of the setting plug.
11

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BS 919-3:2007
Figure 5 Effective diameter tolerance zones of gauges for external product threads having pitch diameter tolerances
above 80 4m and up to 125 4m

NOT GO wear cheek plug Wear limit for solid and adjustable
for solid and adjustable GO screw ring gauge
GO screw ring gauge

NOT GO check plug

for new solid
GO screw ring gauge

GO (Upper limit of product thread)

Solid GO screw ring gauge Setting plug for adjustable

GO screw ring gauge
GO check plug for new solid GO screw ring gauge Setting plug
for GO screw calliper gauge
Not for Resale

NOT GO wear check plug for

Direction of wear of gauges

solid and adjustable

NOT GO screw ring gauge Td 2
NOT GO check plug for Setting plug for
new solid NOT GO screw ring gauge adjustable NOT GO
screw ring gauge and
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NOT GO screw calliper gauge

NOT GO (Lower limit of product thread)

Solid NOT GO
screw ring gauge
Wear limit for
GO check plug for new solid solid and adjustable
NOT GO screw ring gauge NOT GO screw ring gauge
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Copyright British Standards Institution Figure 6 Effective diameter tolerance zones of gauges for external product threads having pitch diameter tolerances
above 200 4m and up to 315 4m

NOT GO wear check plug for solid and

adjustable GO screw ring gauge
Wear limit for solid and
NOT GO check plug adjustable GO screw
for new solid GO screw ring gauge
ring gauge
GO (Upper limit of product limit)

Direction Solid GO screw

of wear ring gauge Setting plug for adjustable
of gauges GO screw ring plug
GO check plug for new
solid GO screw ring gauge Setting plug for GO
screw calliper gauge
Not for Resale

NOT GO wear check plug for solid and Td 2

adjustable NOT GO screw ring gauge
Setting plug for adjustable
NOT GO check plug for new solid NOT GO screw ring gauge
NOT GO screw ring gauge and NOT GO screw
calliper gauge
NOT GO (Upper limit of product limit)

Solid NOT GO
screw ring gauge Wear limit for solid and adjustable
© BSI 2007

BS 919-3:2007
NOT GO screw ring gauge
GO check plug for new
solid NOT GO screw ring gauge
13•

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 BS 919-3:2007

Figure 7 Effective diameter tolerance zones of gauges for internal

product threads having pitch diameter tolerances
above 80 4m and up to 125 4m

NOT GO
Upper limit of product thread

Wear limit of
NOT GO screw
plug gauge NOT GO screw plug gauge
TD2
Direction GO GO screw plug gauge
of wear Lower limit
of gauge of product
thread

Wear limit of GO
screw plug gauge

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Figure 8 Effective diameter tolerance zones of gauges for internal

product threads having pitch diameter tolerances
above 200 4m and up to 315 4m

NOT GO
(Upper limit of product thread)

Wear limit
of NOT GO
screw plug
gauge NOT GO screw
plug gauge

Direction
of wear
of gauge
TD2

GO screw plug
gauge

GO (Lower
limit of
product
thread)

Wear limit of GO screw plug gauge

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 BS 919-3:2007

Table 5 External product thread deviations for effective diameters of

GO screw limit gauges and their associated check plugs and
setting plugs
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7 8 9 10 11 12

Effective New solid GO GO check plug NOT GO check NOT GO wear Setting plug for
diameter screw ring gauge for ring gauge plug check plug adjustable GO
tolerance on and setting plug screw ring gauge
external product for calliper
thread Td2 gauge

Effective diameter deviations from maximum effective diameter limit of external

product thread
--`,,```,,,,````-`-`,,`,,`,`,,`---

Above Up to Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower
(24) 50 +8 0 p3 p9 +11 +5 +16 +10 +4 p2
50 80 +7 p3 p6.5 13.5 +10.5 +3.5 +16.5 +9.5 +2 p5
80 125 +5 p9 p13 p21 +9.5 +0.5 +17.5 +8.5 p2 p10
125 200 +1 p17 p21.5 p30.5 +6.5 p4.5 +18.5 +7.5 p8 p17
200 315 p0.5 23.5 p28 p40 +6.5 p7.5 +20.5 +6.5 p12 p24
315 500 p5 p35 p39.5 p54.5 +4 p14 +22 +4 p20 p35
500 670 p9 p47 p52 p70 +2 p20 +24 +2 p28 p46

Table 6 External product thread deviations for effective diameters of

NOT GO screw limit gauges and their associated check plugs and
setting plugs
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7 8 9 10 11 12

Effective Effective diameter deviations from minimum pitch diameter limit of Setting plug for
diameter external product thread adjustable NOT
tolerance on GO screw ring
external product New solid NOT GO check plug NOT GO check NOT GO wear gauge and NOT
thread Td2 GO screw ring for ring gauge plug check plug A) GO screw
gauge calliper gauge

Above Up to Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower
(24) 50 0 p8 p11 p17 +3 p3 +6 0 p4 p10
50 80 0 p10 p13.5 p20.5 +3.5 p3.5 +7.5 +0.5 p5 p12
80 125 0 p14 p18 p26 +4.5 p4.5 +9.5 +0.5 p7 p15
125 200 0 p18 p22.5 p31.5 +5.5 p5.5 +11.5 +0.5 p9 p18
200 315 0 p23 p27.5 p39.5 +7 p7 +15 +1 p11.5 p23.5
315 500 0 p30 p34.5 p49.5 +9 p9 +19 +1 p15 p30
500 670 0 p38 p43 p61 +11 p11 +23 +1 p19 p37
A) The use of a NOT GO wear check plug for a NOT GO screw ring gauge is not recommended in this British Standard.
The limit of wear should be controlled by the use of the NOT GO check plug (Columns 7 and 8).

16 • © BSI 2007
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 BS 919-3:2007

Table 7 External product thread deviations for effective diameters of

NOT GO screw limit gauges and their associated check plugs and
setting plugs
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7 8

Effective diameter GO screw plug gauge NOT GO screw plug gauge

tolerance on internal
product thread New gauge Worn gauge New gauge Worn gauge
Td2 Deviations from minimum effective Deviations from maximum effective
diameter limit of internal product thread diameter limit of internal product thread

Above Up to Upper Lower Lower Upper Lower Lower

(24) 50 +3 p3 p8 +6 0 p3
50 80 +5.5 p1.5 p7.5 +7 0 p4
80 125 +10.5 +1.5 p6.5 +9 0 p5
125 200 +17.5 +6.5 p5.5 +11 0 p6

--`,,```,,,,````-`-`,,`,,`,`,,`---
200 315 +23 +9 p5 +14 0 p8
315 500 +33 +15 p3 +18 0 p10
500 670 +43 +21 p1 +22 0 p12

Copyright British Standards Institution

© BSI 2007 • 17
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 BS 919-3:2007

Table 8 Deviations for minor diameters of new GO and NOT GO screw

ring gauges, major diameters of new GO and NOT GO screw
plug gauges, and plain check plugs for new screw ring gauges
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7 8 9 10 11 12 13 14

Effective New solid GO Adjustable New solid Plain check New GO New NOT GO
diameter screw ring GO screw ring NOT GO plugs for screw plug screw plug
tolerance (see gauge gauge screw ring minor gauge gauge
Note 1) gauge. diameters of
Adjustable GO and NOT
NOT GO GO screw ring
screw ring gauges
gauge

Minor Minor Minor Tolerance Major Major

diameter diameter diameter diameter diameter
deviations deviations deviations deviations deviations
from from from from from
diameter AA) diameter AA) diameter BB) diameter C E) diameter D F)

Above Up to Upper Lower Upper Lower Upper Lower GOC) NOT Upper Lower Upper Lower
GO D)
(24) 50 +4 p4 +8 0 0 p16 p2 +2 +6 p6 +9 p3
50 80 +5 p5 +7 p3 0 p20 p2 +2 +9 p5 +10.5 p3.5
80 125 +7 p7 p5 p9 0 p28 p2 +2 +15 p3 +13.5 p4.5
--`,,```,,,,````-`-`,,`,,`,`,,`---

125 200 +9 p9 +1 p17 0 p36 p2 +2 +23 +1 +16.5 p5.5

200 315 +11.5 p11.5 p0.5 p23.5 0 p46 p3 +3 +30 +2 +21 p7
315 500 +15 p15 p5 p35 0 p60 p4 +4 +42 +6 +27 p9
500 670 +19 p19 p9 p47 0 p76 p5 +5 +54 +10 +33 p11
NOTE 1 Effective diameter tolerance Td2 or TD2 on external or internal product threads respectively.
Td2 for Columns 3 to 10; TD2 for Columns 11 to 14.
NOTE 2 GO screw calliper gauge anvils. The distance from the pitch line to the crests (minor diameter)
is (H/4 ± 5 μm), i.e. (0.216 51P ± 5 μm).
NOT GO screw calliper gauge anvils. The distance from the pitch line to the crests (minor diameter)
is (F1 ± 5 mm). Values of F1 are given in Table 2.
A) Diameter A = basic minor diameter of product thread minus fundamental deviation.
B) Diameter B = minimum effective diameter of external product thread –2F (see Figure 2).
1
C) Apply tolerance to minimum minor diameter of screw ring gauge (Column 4, 6 or 8).
D) Apply tolerance to maximum minor diameter of screw ring gauge (Column 3, 5 or 7).
E) Diameter C = basic major diameter of product thread + fundamental deviation.
F) Diameter D = maximum effective diameter of internal product thread +2F (see Figure 2).
1

18 • © BSI 2007
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 BS 919-3:2007

Table 9 Deviations for major diameters of screw check plugs and setting
plugs for GO screw ring and calliper gauges
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7 8 9 10 11 12

Effective GO screw check NOT GO screw NOT GO screw Setting plugs for adjustable GO
diameter plug for new check plug for wear check plug screw ring gauges
tolerance on solid GO screw new solid GO for solid GO
external product ring gauge and screw ring gauge screw ring gauge Full form Truncated
thread Td2 setting plug for portion of portion of
GO screw double length double length
calliper gauge plug plug

Major diameter Major diameter deviations from Major diameter Major diameter
deviations from diameter BB) deviations from deviations from
diameter AA) diameter AA) diameter BB)

Above Up to Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower
(24) 50 +6 p6 +12 +4 +17 +9 +6 p6 +5 p3
50 80 +7 p7 +12 +2 +18 +8 +7 p7 +3.5 p6.5
80 125 +9 p9 +12 p2 +20 +6 +9 p9 +0.5 p13.5
125 200 +11 p11 +10 p8 +22 +4 +11 p11 p4.5 p22.5
200 315 +14 p14 +11 p12 +25 +2 +14 p14 p7.5 p30.5
315 500 +18 p18 +10 p20 +28 p2 +18 p18 p14 p44
500 670 +22 p22 +10 p28 +32 p6 +22 p22 p20 p58
A) Diameter A maximum major diameter limit of external product thread.
B) Diameter B maximum effective diameter limit of external product thread + 2F1 (see Figure 2).

--`,,```,,,,````-`-`,,`,,`,`,,`---

Copyright British Standards Institution

© BSI 2007 • 19
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 BS 919-3:2007

Table 10 Deviations for major diameters of screw check plugs and setting
plugs for NOT GO screw ring and calliper gauges
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7 8 9 10 11 12

Effective GO screw check NOT GO screw NOT GO screw Setting plugs for adjustable NOT
diameter plug for new check plug for wear check plug GO screw ring gauges and NOT GO
tolerance on solid NOT GO new solid NOT for solid NOT screw calliper gauges
external product screw ring gauge GO screw ring GO screw ring
thread Td2 gauge gauge Full form Truncated
portion of portion of
double length double length
setting plug for plug for
adjustable screw adjustable screw
ring gauges. ring gauges
Setting plug for
screw calliper
gauges

Major diameter Major diameter deviations from Major diameter Major diameter
deviations from diameter BA) deviations from deviations from
diameter BA) diameter BA) diameter CB)

Above Up to Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower
(24) 50 +6 p6 +6 p6 +9 p3 +2 p10 p1 p13
50 80 +7 p7 +7 p7 +11 p3 +2 p12 p1.5 p15.5

--`,,```,,,,````-`-`,,`,,`,`,,`---
80 125 +9 p9 +9 p9 +14 p4 +2 p16 p2.5 p20.5
125 200 +11 p11 +11 p11 +17 p5 +2 p20 p3.5 p25.5
200 315 +14 p14 +14 p14 +22 p6 +2·5 p25·5 p4.5 p32.5
315 500 +18 p18 +18 p18 +28 p8 +3 p33 p6 p42
500 670 +22 p22 +22 p22 +34 p10 +3 p41 p8 p52
A) Diameter B = maximum major diameter limit of external product thread – pitch (effective) diameter tolerance Td2
(see Columns 1 and 2).
B) Diameter C = minimum effective diameter limit of external product thread + 4F1 (see Table 2).

Table 11 External product thread deviations and allowable wear for GO

and NOT GO plain calliper and ring gauges
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7

Major diameter tolerance on GO plain calliper or ring gauge NOT GO plain calliper or ring
external product thread Td gauge

New gauge Worn gauge New gauge

Deviations from maximum major diameter Deviations from minimum

limit of product thread major diameter limit of
product thread

Above Up to Upper Lower Upper Upper Lower

(36) 85 p4 p12 0 +4 p4
85 140 p15 p25 0 +5 p5
140 335 p50 p46 0 +8 p8
335 850 p39 p69 0 +15 p15
850 950 p39 p81 0 +21 p21

20 • © BSI 2007
Copyright British Standards Institution
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 BS 919-3:2007

Table 12 Internal product thread deviations and allowable wear for GO

and NOT GO plain plug gauges
Unit = mm × 0.001 (μm)
1 2 3 4 5 6 7

Minor diameter tolerance on GO plain plug gauge NOT GO plain plug gauge
internal product thread TD1
New gauge Worn gauge New gauge

Deviations from minimum minor diameter Deviations from maximum

limit of product thread minor diameter limit of
product thread

Above Up to Upper Lower Lower Upper Lower

(38) 100 +12 +5 0 +4 p4
100 180 +27 +17 0 +5 p5
180 375 +46 +30 0 +8 p8
375 710 +65 +39 0 +13 p13
710 1 250 +88 +42 0 +23 p23

--`,,```,,,,````-`-`,,`,,`,`,,`---

Copyright British Standards Institution

© BSI 2007 • 21
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No reproduction or networking permitted without license from IHS
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Copyright British Standards Institution
22 • © BSI 2007

BS 919-3:2007
Table 13 External product thread information for calculation of limits for new solid GO screw ring gauges and their
associated check plugs
1 2 3 4 5 6 7 8 9 10 11

Type of Thread form Flank angle Pitch Major diameter Effective diameter Minor diameter Remarks
gauge tolerances tolerance
Deviations

Upper Lower Upper Lower Upper Lower

--`,,```,,,,````-`-`,,`,,`,`,,`---

Solid GO Figure 1b) Table 3 Table 4 Cleared as shown in Table 5 Table 5 Table 8 Table 8 The
screw ring Column 2 Figure 1b) Column 3 Column 4 Column 3 Column 4 deviations
gauge See Table 1, Columns 2 and 3 specified in
Columns 5
to 10 are for
use only when
the screw ring
gauge is
inspected by
direct
measurement
GO screw Figure 1a) Table 3 Table 4 Table 9 Table 9 Table 5 Table 5 Cleared as shown in
check plug for Column 2 Column 3 Column 4 Column 5 Column 6 Figure 1a)
Not for Resale

new solid GO See Table 1, Columns 4 and 5

screw ring
gauge
NOT GO Figure 2a) Table 3 Table 4 Table 9 Table 9 Table 5 Table 5 Cleared as shown in
screw check Column 3 Column 5 Column 6 Column 7 Column 8 Figure 2a)
plug for new See Table 2, Columns 6 and 7
solid GO
screw ring
gauge
Wear check Figure 2a) Table 3 Table 4 Table 9 Table 9 Table 5 Table 5 Cleared as shown in
plug for solid Column 3 Column 7 Column 8 Column 9 Column 10 Figure 2a)
GO screw ring See Table 2, Columns 6 and 7
gauge
NOTE GO and NOT GO plain check plugs may be used to check the minor diameter of the solid GO screw ring gauge. (See 4.6.2 and Table 8.)
No reproduction or networking permitted without license from IHS
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Copyright British Standards Institution

Table 14 External product thread information for calculation of limits for adjustable GO screw ring and calliper
gauges and their associated setting plugs
1 2 3 4 5 6 7 8 9 10 11

Type of Thread form Flank angle Pitch Major diameter Effective diameter Minor diameter Remarks
gauge tolerances tolerance
Deviations

Upper Lower Upper Lower Upper Lower

Adjustable GO Figure 1b) Table 3 Table 4 Cleared as shown in — — Table 8 Table 8 Adjusted to
screw ring Column 2 Figure 1b) Column 5 Column 6 size by means
gauge See Table 1, Columns 2 and 3 of double
length setting
plug
Setting plug Figure 1a) Table 3 Table 4 Table 9 Table 9 Table 5 Table 5 Cleared as shown in Full form
(double Column 2 Column 9 Column 10 Column 11 Column 12 Figure 1a) thread
length) for See remarks Table 3 Table 9 Table 9 See Table 1, Columns 4 and 5 Truncated
adjustable GO (Column 11) Column 3 Column 11 Column 12 thread
--`,,```,,,,````-`-`,,`,,`,`,,`---

screw ring Crests

gauge truncated as
Not for Resale

Figure 2a).
Roots cleared
as Figure 1a)
Adjustable GO Figure 1b) Table 3 Table 4 Cleared as shown in — — Table 8, Table 8, Adjusted to
screw calliper See Note 2 Column 2 Figure 1b) Note Note size by means
gauge See Table 1, Columns 2 and 3 of single
length setting
plug
Setting plug Figure 1a) Table 3 Table 4 Table 9 Table 9 Table 5 Table 5 Cleared as shown in
for adjustable Column 2 Column 3 Column 4 Column 5 Column 6 Figure 1a)
GO screw See Table 1, Columns 4 and 5
calliper gauge
NOTE 1 GO and NOT GO plain check plugs may be used to check the minor diameter of the adjustable GO screw ring gauge. (See 4.6.2 and Table 8.)
NOTE 2 Alternate profiles may be omitted on GO calliper gauges having fine pitches (see Figure 4).
NOTE 3 Wear check plug for adjustable GO screw ring gauge is the same as that for the solid GO screw ring gauge.
© BSI 2007

BS 919-3:2007
23•
No reproduction or networking permitted without license from IHS
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24 • © BSI 2007

BS 919-3:2007
Table 15 External product thread information for calculation of limits for new solid NOT GO screw ring gauges and
their associated check plugs
1 2 3 4 5 6 7 8 9 10 11

Type of Thread form Flank angle Pitch Major diameter Effective diameter Minor diameter Remarks
gauge tolerances tolerance
Deviations

Upper Lower Upper Lower Upper Lower

Solid NOT GO Figure 2b) Table 3 Table 4 Cleared as shown in Table 6 Table 6 Table 8 Table 8 The
screw ring Column 3 Figure 2b) Column 3 Column 4 Column 7 Column 8 deviations
gauge See Table 2, Columns 6 and 7 specified in
Columns 7
to 10 are for
use only when
the screw ring
gauge is
inspected by
direct
measurement
GO screw Figure 1a) Table 3 Table 4 Table 10 Table 10 Table 6 Table 6 Cleared as shown in
check plug for Column 2 Column 3 Column 4 Column 5 Column 6 Figure 1a)
Not for Resale

new solid See Table 1, Columns 4 and 5

NOT GO
screw ring
gauge
NOT GO Figure 1a) Table 3 Table 4 Table 10 Table 10 Table 6 Table 6 Cleared as shown in
screw check Column 2 Column 5 Column 6 Column 7 Column 8 Figure 1a)
plug for new See Table 1, Columns 4 and 5
solid NOT GO
screw ring
gauge
Wear check Figure 1a) Table 3 Table 4 Table 10 Table 10 Table 6 Table 6 Cleared as shown in
plug for solid Column 2 Column 7 Column 8 Column 9 Column 10 Figure 1a)
NOT GO See Table 1, Columns 4 and 5
screw ring
gauge
NOTE GO and NOT GO plain check plugs may be used to check the minor diameter of the solid NOT GO screw ring gauge. (See 4.6.2 and Table 8.)

--`,,```,,,,````-`-`,,`,,`,`,,`---
No reproduction or networking permitted without license from IHS
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--`,,```,,,,````-`-`,,`,,`,`,,`---

Table 16 External product thread information for calculation of limits for adjustable NOT GO screw ring and
calliper gauges and their associated setting plugs
1 2 3 4 5 6 7 8 9 10 11

Type of Thread form Flank angle Pitch Major diameter Effective diameter Minor diameter Remarks
gauge tolerances tolerance
Deviations

Upper Lower Upper Lower Upper Lower

Adjustable Figure 2b) Table 3 Table 4 Cleared as shown in — — Table 8 Table 8 Adjusted to
NOT GO Column 3 Figure 2b) Column 7 Column 8 size by means
screw ring See Table 2, Columns 6 and 7 of double
gauge length setting
plug
Setting plug Figure 1a) Table 3 Table 4 Table 10 Table 10 Table 6 Table 6 Cleared as shown in Full form
(double Column 2 Column 9 Column 10 Column 11 Column 12 Figure 1a) thread
length) for See remarks Table 3 Table 10 Table 10 See Table 1, Columns 4 and 5 Truncated
adjustable (Column 11) Column 3 Column 11 Column 12 thread
NOT GO Crests
screw ring truncated as
gauge
Not for Resale

Figure 2a)
Roots cleared
as Figure 1a)
Adjustable Figure 2b) Table 3 Table 4 Cleared as shown in — — Table 8, Table 8, Adjusted to
NOT GO Column 3 Figure 2b) Note Note size by means
screw calliper See Table 2, Columns 6 and 7 of single
gauge length setting
plug.
Setting plug Figure 1a) Table 3 Table 4 Table 10 Table 10 Table 6 Table 6 Cleared as shown in
for adjustable Column 2 Column 9 Column 10 Column 11 Column 12 Figure 1a)
NOT GO See Table 1, Columns 4 and 5
screw calliper
gauge
NOTE 1 GO and NOT GO plain check plugs may be used to check the minor diameter of the adjustable NOT GO screw ring gauge. (See 4.6.2 and Table 8.)
NOTE 2 The anvil shall contact the product thread on two flanks only, and on gauges having fine pitches these flanks shall be not more than three pitches
© BSI 2007

BS 919-3:2007
apart (see Figure 5).
NOTE 3 Wear check plug for adjustable NOT GO screw ring gauge is same as that for solid NOT GO screw ring gauge.
25•
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Copyright British Standards Institution
26 • © BSI 2007

BS 919-3:2007
Table 17 Internal product thread information for calculation of limits for GO and NOT GO screw plug gauges
1 2 3 4 5 6 7 8 9 10 11

Type of Thread form Flank angle Pitch Major diameter Effective diameter Minor diameter Remarks
gauge tolerances tolerance
Deviations

Upper Lower Upper Lower Upper Lower

GO screw Figure 1a) Table 3 Table 4 Table 8 Table 8 Table 7 Table 7 Cleared as shown in
plug gauge Column 2 Column 11 Column 12 Column 3 Column 4 Figure 1a)
See Table 1, Columns 4 and 5
NOT GO Figure 2a) Table 3 Table 4 Table 8 Table 8 Table 7 Table 7 Cleared as shown in
screw plug Column 3 Column 13 Column 14 Column 6 Column 7 Figure 2a)
gauge See Table 2, Columns 6 and 7
Not for Resale

--`,,```,,,,````-`-`,,`,,`,`,,`---
 BS 919-3:2007

Annex A (informative) Function and method of use of

various gauge types
A.1 Gauges for internal screw threads
A.1.1 GO screw plug gauge
This gauge checks that the virtual effective diameter and the major
diameter of the product thread are not smaller than the minimum limits
specified. It does not check the minimum minor diameter of the product
thread since, for practical reasons, the root of the plug gauge has to be
cleared.
The minor diameter is examined separately by means of a GO plain plug
gauge made to the minimum minor diameter of the internal thread. It
has to be possible to screw the GO screw plug gauge by hand, without
using excessive force, into the complete length of the product thread.
This gauge does not take account of any eccentricity between the crest
and flank diameters of the internal product thread which might affect
assembly. Any such eccentricity can be identified using a GO screw plug
gauge provided with a pilot GO plain plug, the diameter of which is
made to the minimum minor diameter of the internal thread. This
ensures that:
• the effective diameter of the external thread does not exceed the
maximum size specified for it; and
• the external thread will assemble with an internal thread having a
minimum minor diameter.
Such a gauge does not ensure that the major diameter of the external
thread is not too large since, for practical reasons, the root of the ring
gauge has to be cleared.
The major diameter is examined separately by means of a GO plain
calliper gauge made to the maximum major diameter of the external
thread (see A.2.3). Here again any eccentricity between the crest and
flank diameters of the thread will not be detected by the GO gauge. The
amount of any eccentricity present is most readily determined by means
of optical projection.
Since its purpose is to ensure, as far as possible, assembly of mating
threads, a GO screw gauge should be perfect form and equal to the
maximum metal size of the products being inspected.
NOTE When, for reasons of economy, standard gauge blanks are used in
the manufacture of the gauge, the length of the gauge might be less than the
length of engagement of the product threads. Suitable precautions have
therefore to be taken when using the gauge.

A.1.2 NOT GO screw plug gauge

This gauge checks that the maximum effective diameter of the product
thread is not too large. Ideally it should not be possible for the gauge to
enter the product thread but, as internal threads are often slightly
bell-mouthed, it is permissible to allow entry provided that, on
withdrawal, disengagement takes place within two full turns of thread.
If the product has a length of thread of three turns or less, the gauge
should not screw completely through the product thread. The gauge
should be applied by hand without using excessive force.

Copyright British Standards Institution

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 BS 919-3:2007

A.1.3 GO and NOT GO plain plug gauges

These gauges check that the minor diameter of the product thread is
between its specified limits. The GO plain plug gauge should assemble
completely with the product thread. The NOT GO plain plug gauge may
enter the product thread by not more than a distance of two full turns
of the thread. If the product has a length of thread of three turns or less,
the NOT GO gauge should not pass completely through the product
thread.

A.2 Gauges for external screw threads

A.2.1 Solid or adjustable GO screw ring gauge

This gauge checks that the virtual effective diameter of the product
thread is not too large. The major and minor diameters of the product
thread are not checked by this gauge. It should be possible to screw the
gauge by hand, without using excessive force, over the complete length
of the product thread.

A.2.2 Solid or adjustable NOT GO screw ring gauge

This gauge checks that the effective diameter of the product thread is
not too small. Ideally it should not be possible for the product thread to
enter the gauge but, as external threads are often slightly tapered at the
leading end, it is permissible to allow entry provided that, on
withdrawal, disengagement takes place within two full turns of thread.
If the product has a length of thread of three turns or less the gauge
should not screw completely on to the product thread. The gauge should
be applied by hand without using excessive force.

A.2.3 Adjustable GO screw calliper gauge

This gauge is intended to check that the virtual effective diameter of the
product thread is not too large. The major and minor diameters of the
product thread are not checked by this gauge. The gauge is generally
applied to the product thread under its own weight or in accordance
with a fixed working load at three positions at least evenly spaced
around the circumference of the thread. The gauge should pass
completely over the product thread at any of the positions at which it is
applied.

A.2.4 Adjustable NOT GO screw calliper gauge

This gauge checks that the effective diameter of the product thread is
not too small. It is generally applied to the product thread under its own
weight or under a fixed working load at three positions evenly spaced
around the circumference of the thread. The gauge should not pass over
the product thread except possibly for the first two turns of thread.

A.2.5 GO and NOT GO plain ring or calliper gauges

These gauges check that the major diameter of the product thread is
between the specified limits. The gauges are applied to the product
thread under the same conditions as the corresponding screw gauges.

--`,,```,,,,````-`-`,,`,,`,`,,`---

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 BS 919-3:2007

A.2.6 Setting plugs (double length) for adjustable GO and

NOT GO screw ring gauges
These setting plugs are used to set adjustable screw ring gauges to the
specified effective diameters. Each setting plug has a length of thread
approximately equal to twice the length of the screw ring gauge to be
controlled. The effective diameter of the setting plug is constant
throughout, but half the length of the setting plug has a full form thread
and the remaining half has a truncated form of thread. The screw ring
gauge is adjusted to be a snug fit on the full form portion of the setting
plug. The setting plug is then unscrewed by hand, without using
excessive force, through the screw ring gauge until the truncated
portion of the setting plug completely engages the screw ring gauge. In
the latter condition there should be no perceptible shake or play
between the setting plug and the screw ring gauge: shake or play is an
indication of an unacceptable error of thread form of the adjustable
screw ring gauge.

A.2.7 Setting plugs (single length) for adjustable GO and

NOT GO screw calliper gauges
These setting plugs are used to set the adjustable screw calliper gauges,
and are approximately equal in length to the gauges. The setting plugs
for the GO and NOT GO screw calliper gauges have full form threads. A
calliper gauge is adjusted so that it just passes over the appropriate
setting plug under its own weight or under a fixed working load.
For any given product size, setting plugs for calliper gauges are made
slightly smaller in effective diameter than the corresponding setting
plugs for adjustable ring gauges. This difference in size permits the
results obtained by a calliper gauge to be compared with those obtained
with an adjustable ring gauge.
Single-length setting plugs provide little help in detecting any error in
thread form caused by wear of the calliper gauge anvils, so it is
necessary to examine periodically for such error by other means.

A.2.8 Screw check plugs for new solid GO and NOT GO

screw ring gauges
These screw check plugs are used to check that the effective diameters
of screw ring gauges are within the specified limits. It should be possible
to screw the GO check plug by hand completely through the appropriate
screw ring gauge. The NOT GO check plug, when screwed by hand
without excessive force, may be allowed to enter both ends of the screw
ring gauge provided that, on withdrawal, disengagement takes place
within one full turn of thread.
When setting a new calliper gauge with the setting plugs discussed
in A.2.7, an additional check should be made with the NOT GO check
plug for the corresponding new screw ring gauge. The latter check may
also be applied to a used calliper gauge to ensure that the thread form
is not worn. The wear check plug for the screw ring gauge should not
be used as a wear check plug for the calliper gauge.

Copyright British Standards Institution

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 BS 919-3:2007

A.2.9 Plain check plugs for new solid GO and NOT GO screw
ring gauges
These check plugs are used to verify that the minor diameter of a screw
ring gauge is between the specified limits. A GO check plug should
assemble completely with the screw ring gauge. A NOT GO check plug
may enter both ends of the screw ring gauge by not more than a distance
of one turn.

A.2.10 NOT GO screw wear check plugs for used solid GO

and NOT GO screw ring gauges
These wear check plug gauges are used to check that the appropriate
solid screw ring gauges have not worn beyond the specified limits of
wear.
A wear check plug gauge, when screwed by hand without excessive
force, may be allowed to enter both ends of the screw ring gauge
provided that, on withdrawal, disengagement takes place within one full
turn of thread.

A.3 Check gauges

GO and NOT GO screw check gauges verify that new solid type ring
gauges are within limits. They correspond to the GO and NOT GO screw
plug gauges used for testing the product but are made to much finer
tolerances. They serve as an alternative to direct measurement in the
testing of ring gauges above, say, 14--- inch in diameter. Check gauges are
indispensable for sizes smaller than 1--4- inch in diameter, which is about
the limit of size for direct measurement.
NOT GO effective diameter checks also ensure that solid GO ring
gauges are not allowed to remain in service after they have worn by a
specific amount.

A.4 Use of screw gauges

It is not necessary for all the different types of screw gauges described
in A.2.1 and A.2.2 to be used for checking external threads on
products, but it is essential for one of the types of GO screw gauges and
one of the types of NOT GO screw gauges to be used.
A solid or adjustable GO screw ring gauge should always be used for
gauging the maximum effective diameter of an external thread but, to
save time in checking, a GO screw calliper gauge may be employed.
Gauging with a GO screw calliper gauge should be supplemented by
random sampling with a GO screw ring gauge to give greater assurance
that parts outside the limits are not accepted. In cases of dispute,
gauging with a GO screw ring gauge is decisive.
A GO screw calliper gauge should not be used if the manufacturing
process is likely to introduce errors in the product thread which this
gauge is not certain to detect, e.g. lobing, local pitch errors in milled
threads and burrs at the start of the thread. Further, a GO screw calliper
gauge is not suitable for checking non-rigid, e.g. thin-walled, parts
which would deform when the gauge is applied; in such cases a GO
screw ring gauge should be used.

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For large screw threads (over about 100 mm diameter) the size to which
the GO screw calliper gauge is set may be reduced to compensate for
the effect of form errors that may occur in these threads; this reduces
the possibility of accepting screw threads that are outside the specified
limits.
A NOT GO screw calliper gauge should be used to check the minimum
effective diameter of an external thread. The solid or adjustable
NOT GO screw ring gauge should only be used to check non-rigid
product threads, e.g. those on thin-walled parts which would deform if
a NOT GO screw calliper were applied.

Annex B (informative) Inspection procedures and the

settlement of disputes
B.1 Method of inspection of product threads
The product manufacturer should ask the purchaser which procedure is
to be employed for the inspection of the product threads when the order
is made.

B.2 Inspection by the manufacturer

Generally speaking, where product threads are also checked at the
manufacturer’s works, the inspection department can use the same kind
of gauges as the workshop. In order to avoid differences between the
results obtained by the workshop and the inspection department, the
workshop should use new or only slightly worn GO gauges while the
inspection department is provided with GO gauges the effective
diameter of which lies nearer the permissible wear limit. The reverse
procedure should be adopted for NOT GO gauges.
In case of dispute, the product threads are regarded as satisfactory
when the gauges with which they are checked and passed conform to
the sizes specified for those gauges, including the permissible wear
limits. This can be proved by measuring the gauges or by checking them
with the check plugs specified.
NOTE In some special cases where it is essential to ensure that threads
which could be outside the limits are not accepted and in the case of GO
gauges used for sample inspection, gauges which have worn beyond the
maximum metal limit of the product thread should not be used.

B.3 Inspection by the purchaser

There are three possible procedures for inspection on behalf of the
purchaser by an inspector who is independent of the manufacturing
plant concerned.
a) The inspector may gauge the product threads with the
manufacturer’s own gauges. In this case, he should check the
accuracy of the ring or calliper gauges employed by means of
check plugs and setting plugs which belong either to the
manufacturer or to the inspector (purchaser). Screw plugs should
be checked by direct measurement.
b) The inspector may use his own gauges made in accordance with
this standard for gauging product threads. In this case, the
recommendations in B.2 for checking during manufacture and the
procedure for settling disputes apply.
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c) The inspector may use his own inspection gauges for checking the
product threads. The disposition of the tolerance zones for these
gauges should be such as to ensure that the purchaser does not
reject product threads the actual size (e.g. effective diameter) of
which lies within the limits specified for the product.

Annex C (informative) Reference temperature

In accordance with BS EN ISO 1, the sizes of both the gauge and the
workpiece are related to the standard reference temperature of 20 °C,
deviation from which by even a few degrees can cause dimensions to
vary by an undesirable percentage of tolerance.
If the workpiece and the gauge have the same thermal coefficient of
expansion (e.g. both are of steel construction), the checking
temperature can deviate from 20 °C without detriment to the result,
always provided that the temperature of both the gauge and the
workpiece is the same at the time of gauging.
If the workpiece and gauge have different thermal coefficients of
expansion (e.g. steel workpiece and carbide gauge or brass workpiece
and gauge of steel or carbide), the temperature of the gauge and the
workpiece should, in principle, be close to 20 °C at the time of gauging.

Annex D (informative) Hardness

A steel gauge should be hardened to the value most appropriate to its
type, size and pitch and to the steel from which it is made.
Experience has shown that if the hardness of steel gauges is kept within
the range 650 HV to 800 HV (57 HRC to 62 HRC) the threads do not
easily burr nor are they brittle.
Experience has also shown that the gauging surfaces of plain plug and
calliper gauges should be hardened within the range 750 HV to 850 HV
(61 HRC to 63 HRC).

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Bibliography
BS 3643 (both parts), ISO metric screw threads
BS 6528:1984, ISO 5408:1983, Glossary of terms for cylindrical
screw threads
BS EN ISO 1, Geometrical product specifications (GPS) –
Standard reference temperature for geometrical product
specification and verification
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