Thread & plain gauges, built to the standard.

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Metric thread gauges

Metric thread plug and ring gauges manufactured to DIN ISO 1502. GO and NOT-GO members verify pitch diameter and functional fit across the full metric range.

Representative sizes & classes

Diameter	Pitch	Plug class	Ring class
M1	0.25 mm	5H	6h
M2	0.40 mm	6H	6g
M3	0.50 mm	6H	6g
M4	0.70 mm	6H	6g

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Unified thread gauges

Unified inch thread gauges manufactured to ANSI / ASME B1.2 standards, covering UNC, UNF and UN series with GO / NOT-GO plug and ring members.

Representative sizes & classes

Diameter	TPI	Plug	Ring class
No. 0 – UNF	80 TPI	GO / NOGO	2A
1/4 – UNC	20 TPI	GO / NOGO	2A
1/2 – UNC	13 TPI	GO / NOGO	2A
1 – UNC	8 TPI	GO / NOGO	2A

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“G” pipe gauges

“G” parallel pipe thread gauges manufactured to ISO 228-2 / DIN EN ISO 228-2, for fittings where the seal is made outside the thread.

Representative sizes & classes

Size	TPI	Plug class	Ring class
G1/16	28 TPI	General	A & B
G1	11 TPI	General	A & B
G4	11 TPI	General	A & B
G6	11 TPI	General	A & B

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Taper gauges (NPT)

NPT taper thread gauges manufactured to ANSI / ASME B1.20.1. Our expertise also covers non-standard designs: extra lengths, air grooves, pilots and depth steps.

Representative sizes & classes

Member	Type	Acceptance
External thread	Basic step ring	Flush within a single turn
External thread	Min/max step ring	Face between min & max step
Internal thread	Basic / min-max plug	Flush within limits

External threads: when screwed on by hand, the basic step gauge should be flush with the component face within a single turn. Internal threads: with a min/max step gauge, the component face should sit flush between the minimum and maximum step limits.

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NPTF & ANPT gauges

NPTF gauges to ANSI / ASME B1.20.5 and ANPT to SAE AS71051B. Dry-seal threads need controlled truncation, verified with L1 & L3 plug and L1 & L2 ring gauges plus crest-check members.

Representative sizes & classes

Thread	Standard	Plug gauges	Ring gauges
NPTF	ANSI/ASME B1.20.5	L1 & L3 (basic / min-max)	L1 & L2 (basic / min-max)
ANPT	SAE AS71051B	6-step crest crack plug	6-step crest crack ring

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ACME & Stub ACME

ACME power thread gauges to ASME B1.5 and Stub ACME to ANSI B1.8. 2G is the common class; 3G and 4G are available where less backlash is required.

Representative sizes & classes

Type	Standard	Classes
ACME	ASME B1.5	2G · 3G · 4G
Stub ACME	ANSI B1.8	2G · 3G · 4G

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Trapezoidal gauges

Trapezoidal thread gauges manufactured to DIN 103-9. Tolerance 7H/7e is recommended for medium quality and 8H/8c for coarse quality.

Representative sizes & classes

Quality	Nut	Bolt
Medium	7H	7e
Coarse	8H	8c

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Taper pipe threads

Taper pipe thread gauges for pressure-tight joints — ISO 7-R, BSPT and PT threads with a 55° thread angle, manufactured to ISO 7-2, EN 10226, BS 21 and JIS B0253.

Representative sizes & classes

Thread	Angle	Standard
ISO 7-R	55°	ISO 7-2
BSPT	55°	BS 21
PT	55°	JIS B0253

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Snap gauges

Snap gauges for checking outside dimensions such as external diameters — large contact area, apt contact pressure and superior wear resistance. Available in customized dimensions.

Representative sizes & classes

Type	Range
Single-end progressive	Ø3 – 160 mm
Double-ended, separate GO/NOGO	Ø3 – 100 mm
Double-ended I-type	Ø100 – 300 mm

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Plain plug & ring gauges

Plain plug and ring gauges — GO gauges in tungsten carbide and NO-GO in steel, in Reversible and Trilock styles. Custom diameters from 1–400 mm to I.S., B.S. and DIN standards.

Representative sizes & classes

Style	Range	Material
Reversible	Ø0.5 – 8 mm	Carbide / steel
Trilock	Ø8 – 100 mm	Carbide / steel
Trilock plate & paddle	Ø100 – 400 mm	Carbide / steel