THREAD GAUGES

ISO metric thread gauges	NPT / NPTF / PTF thread gauges
UNIFIED (UN) thread gauges	Other types of gauges
Gas (G) thread gauges	Limit plug gauges, setting rings
BSW / BSF / Whitworth gauges	Master check gauges
ACME / STUB ACME gauges	Wear check gauges

Thread gauges

1. ISO metric thread gauges (2 - 200 mm)

Specification:

ISO standard	Basic dimensions: ISO 724 - 1993(E) & ISO 965/1 - 1998(E)
	Gauging practice: ISO-1502 - 1996
DIN standard	Basic dimensions & gauging practice: DIN 13
JIS standard	Basic dimensions: JIS B 0205 & JIS B 0209
	Gauging practice: JIS B 0251-1998
ANSI & BS standards use unilateral tolerances for gauges. These gauges are manufactured only against specific customer orders and require minimum order quantity.
ANSI standard	Basic dimensions: ANSI/ASME B 1.13 M
	Gauging practice: ANSI/ASME B 1.16 M 1984

For inquiries please specify:

diameter and pitch of the thread
thread type (right or left handed)
gauge type (plug or ring)
tolerance class

Recommended tolerance classes for internal threads (thread plugs)
Fine Medium Coarse	Tolerance position 'G'			Tolerance position 'H'
	S	N	L	S	N	L
	-	-	-	4H	5H	6H
	(5G)	6G	(7G)	5H	6H	7H
	-	(7G)	(8G)	-	7H	8H

Recommended tolerance classes for external threads (thread rings)

Fine
Medium
Coarse

Tolerance position 'e'

Tolerance position 'f'

Tolerance position 'g'

Tolerance position 'h'

(4g)

(5g4g)

(3h4h)

(5h4h)

(7e6e)

(5g6g)

(7g6g)

(5h6h)

(7h6h)

(8e)

(9e8e)

(9g8g)

S = short length of thread engagemen, N = normal length of thread engagemen, L = long length of thread engagement

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2. UNIFIED thread gauges (No.4 - 8")

Gauging practice: conform ANSI/ASME B1.2 - 1983

Diameter - TPI combination:

UNC - Unified National Coarse
UNF - Unified National Fine
UNEF - Unified National Extra Fine
UN - Unified National Constant (uniform TPI series)
UNS - Unified National Special

Thread plugs under 2.1/2" nominal diameter(inclusive) are manufactured double-ended (Go-NoGo) and above single-endend (Go or NoGo).

Tolerance class

Tolerance class for plug gauges (internal threads)

Tolerance class for ring gauges (external threads)

Application

where quick assembly is needed even when threads are dirty / damaged, wide tolerances for male and female threads

corresponds to medium fit and used for general applications which requires free assembly

where closer fit is required

AG class thread ring gauges are used in lubricant and high temperature applications.

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3. Gas thread gauges (G1/8" - G6")

Specification:

ISO standard	Basic dimensions: ISO 228 (1) - 1994 (E)
ISO standard	Gauging practice: ISO 228 (2) - 1987
BSI standard	B.S. 2779 - 1986
JIS standard	B 0202 - 1999

Manufacturing range
Pipe diameter	TPI	Tolerance class
		Internal threads - plug gauges	External threads - ring gauges
1/16, 1/8	28	Only general class	clasa B
1/4, 3/8	19		Class A
1/2, 5/8, 3/4, 7/8, (1.1/16), 1.1/8, 1.1/4, (1.3/8)	14 11		Tolerance for class 'A' rings is closer/tighter than class 'B'
1.1/2, (1.5/8), (1.7/8), 2, (2.1/8), 2.1/4, (2.3/8), 2.1/2	11
2.3/4, (2.7/8), 3, (3.1/4), 3.1/2, 4	11
4.1/2, 5, 5.1/2, 6	11

Pipe diameters in paranthesis () are not recommended in above refered ISO specifications but can be manufactured on request.

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4. BSW / BSF / Whitworth thread gauges (1/8" + 6")

Specification:
Basic dimensions: B.S. 84 - 1956
Gauging practice: B.S. 919 Part II - 1971

Tolerance class
Internal threads (plug gauges)	External threads (ring gauges)
Medium class Normal class Close class	Medium class Free class Close class

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5. ACME / STUB ACME thread gauges (1/4" + 5")

Specification:

ACME	American specification: ANSI/ASME B1.5 - 1997
ACME	B.S. specification: B.S. 1104 - 1957
STUB ACME	ANSI/ASME B1.8 - 1988

Manufacturing range
	Diameter	TPI	Tolerance class
Thread plug gauges	1/4" - 5" (5"+ - 14" can be supplied on request)	16, 14, 12, 10, 8, 6, 5, 4, 3, 2.5, 2	2G, 3G, 4G 2C, 3C, 4C
Thread ring gauges	1/4" - 5" (5"+ - 14" can be supplied on request)	16, 14, 12, 10, 8, 6, 5, 4, 3, 2.5, 2	2G, 3G, 4G 2C, 3C, 4C

'3G' tolerance class is the most commonly used. Classes above 3 are tighter.

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6. NPT / NPTF / PTF thread gauges (1/16" + 6")

Specification:
'Basic' type: ANSI/ASME B1.20.1 - 1983
'Step Limit' type: H-28 Part II - 1957

'BASIC' type: has one step for plugs and one surface in case of ring gauges. This step/surface represents the basic pitch diameter.
'STEP LIMIT' type: has three steps on the gauge. These steps correspond to minimum, basic and maximum size of components.

Manufacturing range
Diameter [inch]	TPI
1/16"	27
1/8"	27
1/4"	18
3/8"	18
1/2"	14
3/4"	14
1"	11.1/2
1.1/4"	11.1/2
1.1/2"	11.1/2
2"	11.1/2
2.1/2"+	8

Types of NPT gauges
A) NPT L1 - is the most frequently used for checking up to L1 length of component, suitable for hand tight engagement.
B) NPT L2 - used when checking threads beyond the limit L1 is required, up to L2 length, suitable for checking with wrench.

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7. Other types of thread gauges

MJ thread gauges - as per ISO 5855 Part I,II,III - 1981; ANSI B1.21M - 1978
UNJ thread gauges - as per B.S. 4084 - 1978; ISO 3161 - 1977
B.S. thread gauges - as per B.S. 31 - 1940
B.A. thread gauges - as per B.S. 919 Part II - 1971
B.S. Cycle thread gauges - as per B.S. 919 Part II - 1971
PG thread gauges - as per DIN 40430 - 1971 & DIN 40431 - 1972
Trapezoidal thread gauges - as per DIN 103 - 1977
Line Pipe (LP) thread gauges
UPTBG thread gauges
Buttress thread gauges
BSPTr / 'R' ISO 7/1&2 thread gauges
Other special thread gauges on request

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Limit plug gauges, setting rings

Limit plug gauges, setting rings

Specification:
Limit plugs: DIN 7162 si DIN 7164
Setting rings: DIN 2250 C, DIN ISO 286/1

Features:

from special steel, hardened, ground and lapped
possible to be delivered hard chromed

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Check gauges

1. Master check gauges

Features:

used to check NEW thread gauges
the checking of new Go thread ring gauges is done with a master check plug Go-NoGo. Similary, the master check plug for NoGo ring will be used for checking the NoGo ring gauge.

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2. Wear check gauges (WCG)

Features:

used for checking wear of USED thread gauges (whether or not they are in the accepted tolerances)
are designed in such a manner that, when WCG enters its corresponding thread gauge, it indicates that, the gauges is worn out or not
WCP for Go and NoGo thread ring are supplied separately

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