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
Metric gauges
Recommended tolerance classes for internal threads (thread plugs)
Fine
Medium
Coarse
Tolerance position 'G' Tolerance position 'H'
SNLSNL
---4H5H6H
(5G)6G(7G)5H6H7H
-(7G)(8G)-7H8H

Recommended tolerance classes for external threads (thread rings)
Fine
Medium
Coarse
Tolerance position 'e' Tolerance position 'f' Tolerance position 'g' Tolerance position 'h'
SNLSNLSNLSNL
-------(4g)(5g4g)(3h4h)4h(5h4h)
-6e(7e6e)-6f-(5g6g)6g(7g6g)(5h6h)6h(7h6h)
-(8e)(9e8e)----8g(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).

Unified thread gauges
Tolerance class
Tolerance class for plug gauges (internal threads) Tolerance class for ring gauges (external threads) Application
1B1Awhere quick assembly is needed even when threads are dirty / damaged, wide tolerances for male and female threads
2B2Acorresponds to medium fit and used for general applications which requires free assembly
3B3Awhere 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)
Gauging practice: ISO 228 (2) - 1987
BSI standard B.S. 2779 - 1986
JIS standard B 0202 - 1999
Gas thread gauges
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
BSW thread gauges
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5. ACME / STUB ACME thread gauges (1/4" + 5")
  Specification:
ACME American specification: ANSI/ASME B1.5 - 1997
B.S. specification: B.S. 1104 - 1957
STUB ACME ANSI/ASME B1.8 - 1988
ACME thread gauges
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.
NPT thread gauges
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
Other types of thread gauges
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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
Limit plugs & setting rings
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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.
Master check gauges
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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
Wear check gauges
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