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External checker M3 6g Go
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  • External checker M3 6g Go - nr. 1
Varel

M4 ring gauge 6g Go

Varel Varel
34368
€30.75 tax inc.

Net price: €25.00

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W magazynie: 10-100 szt.
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Call and order: (44) 755-04-05

Description

ThreadM4 × 0.7
Tolerance class6g
SetGO + NO-GO
StandardISO 1502

Technical specifications of the M4 × 0.7 thread ring gauge

Gauge set specifications according to ISO 1502

Technical data
Gauge type GO + NO-GO thread ring gauge set
Thread M4 × 0.7 mm
Tolerance class 6g
Nominal diameter (d) Ø4.000 mm
Pitch diameter (d2) 3.545 mm
d2 range for 6g 3.433 – 3.523 mm
Thread pitch (P) 0.7 mm
Thread angle 60°
Material Tool steel, hardened
Hardness 58–62 HRC
Gauge standard ISO 1502 / DIN 2285 + DIN 2299
Thread standard ISO 965-1 / DIN 13-1
Reference temperature 20 °C
Manufacturer Varel
M4-6g ring gauge set: GO marked T and NO-GO marked Z with a groove
T
GO ring gauge — screwed on by hand along the full bolt thread.
Z
NO-GO ring gauge with a groove in the knurled surface — stops after no more than 2 turns.
The M4-6g engraving on the face of both rings indicates the size and tolerance class of the bolt being inspected.

Limit gauging principle: GO + NO-GO

Gauge for M4 external threads according to ISO 1502

M4-6g GO ring gauge screwed on by hand along the full thread of a hex-head bolt
1
The GO ring gauge is screwed on by hand, without force, along the full thread of the M4 x0.7 bolt.
M4-6g NO-GO ring gauge stops on the bolt thread after 2 turns
2
The NO-GO ring gauge stops after no more than 2 turns — turns are counted when unscrewing.
Inspection result with the M4-6g set: GO passed, NO-GO stopped, bolt meets class 6g
3
The GO ring gauge passed, NO-GO stopped — the bolt meets class 6g.

The pair of ring gauges M4 6g answers a single question: whether this bolt is within tolerance. The ring gauge GO must screw on by hand along the full thread, while the ring gauge NO-GO must stop after no more than 2 turns, counted when unscrewing. The two results give a clear decision — acceptable or requires rework.

This size range is typical for the production of machine bolts and studs. The ring gauge detects both a thread cut too deep and a thread deformed on a shaft — neither defect is visible to the naked eye. The 0.7 mm pitch is the coarse pitch for this diameter: the designation M4 without a specified pitch denotes this thread. For reference: the thread minor diameter M4 is 3.141 mm — this cross section determines the bolt's strength, while the gauge checks the pitch diameter.

The gauge GO has a full thread profile and checks the maximum material limit — pitch diameter, pitch and thread profile at the upper tolerance limit (for M4 6g: d2 max = 3.523 mm). It should screw freely onto the full length of the thread being inspected — without force or wrenches. The gauge NO-GO has a truncated profile with incomplete flanks and checks the minimum material limit (d2 min = 3.433 mm). According to ISO 1502 §7 it must not screw onto the thread more than 2 threads. Only meeting both conditions simultaneously confirms that the thread is within tolerance class 6g.

Thread inspection M4 × 0.7 — class 6g

1 GO gauge

screws on the full length: YES

2 NO-GO gauge

advances max. 2 turns: YES

✓ Conforming thread

class 6g confirmed

Inspection standard: ISO 1502 · Tolerances: ISO 965-1 · Dimensions: ISO 724 / DIN 13-1

Ring gauge set on a bolt: GO passes, NO-GO stops — thread acceptable
✓ Thread acceptable — GO screws onto the full thread, NO-GO stops.
GO ring gauge does not screw onto the bolt — bolt thread oversized
✗ Thread oversized — GO does not screw onto the bolt.
NO-GO ring gauge passes over the bolt thread — thread undersized
✗ Thread undersized — NO-GO screws on more than 2 turns.

Tolerance classes for an M4 × 0.7 external thread

Comparison according to ISO 965-1 for M4 × 0.7

Comparison of classes 4g, 6g, and 6e

Basic pitch diameter d2 for the thread M4 is 3.545 mm. The deviations in the table are measured downward from this value.

Classd2 nominal [mm]d2 permissible [mm]Tolerance zoneApplicationStatus
4g3.545 mm3.467 – 3.523 mm0.056 mmPrecision fit
6g3.545 mm3.433 – 3.523 mm0.090 mmStandard fit — bolts, fastenersTHIS PRODUCT
6e3.545 mm3.399 – 3.489 mm0.090 mmClearance fit — for electroplating

The full range of class 6g for the thread M4 is 0.090 mm — less than the thickness of a sheet of paper: from 3.433 to 3.523 mm. Class 6g is the standard for general-purpose bolts — it mates with 6H nuts. Classes 4g and 5g reduce clearance in guiding joints, while 6e and 8g leave room for electroplating. The values in the table are pitch diameter d2, measured at half the profile height, not the thread major diameter.

Proper use and calibration

Maintaining gauge accuracy

Usage rules according to ISO 1502

Before measurement, the thread is cleaned of chips, burrs, oil and contaminants. The gauge is screwed on by hand only, without wrenches or externally applied torque (which increases wear and distorts the result). Reference inspection temperature: 20 °C. Gauges are stored in a dry place, protected with rust-preventive oil. The calibration interval is determined by the user based on usage intensity — ISO 1502 (clause 7.2.1) requires periodic gauge measurement but specifies neither the interval nor the number of measurements. ISO 1502 specifies thread ring gauge wear limits (wear limits); once these are exceeded, the gauge must be removed from service.

Varel set contents

Included in the set:

✓ 1 × GO thread ring gauge — GO, full thread profile, checks the maximum material limit
✓ 1 × NO-GO thread ring gauge — NO-GO, truncated profile (max. 2 turns of engagement according to ISO 1502)
✓ Tool steel hardened to 58–62 HRC — high wear resistance
✓ Ground thread profiles — high measurement repeatability
✓ Compliance with ISO 1502 / DIN 2285 + DIN 2299 (gauges) and ISO 965-1 / DIN 13-1 (thread)

Frequently asked questions

The principle of limit gauging requires verification of both the maximum and minimum material limits. The GO gauge confirms that the thread is not oversized (it screws on the full length), while the NO-GO gauge confirms that it is not undersized (it does not advance more than 2 turns according to ISO 1502). Using only one gauge leaves the other limit unchecked — the part may be outside tolerance class 6g despite passing a partial inspection.

The gauge GO has a full thread profile and represents the maximum material limit of the external thread being inspected (for M4 6g: d2 max = 3.523 mm). The gauge NO-GO has a profile that is truncated with incomplete flanks — it checks only the pitch diameter at the lower limit (d2 min = 3.433 mm) and has a shorter threaded length (usually 3 full turns). The design of both types is defined by ISO 1502 table 2.

The thread is nonconforming, if either condition occurs: the GO gauge does not screw on the full length (thread oversized — d2 above 3.523 mm) or the NO-GO gauge advances more than 2 turns (thread undersized — d2 below 3.433 mm). In either case, the part must be rejected or reworked. Reference standard: ISO 965-1 (tolerances), ISO 1502 (inspection procedure).

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M4 ring gauge 6g Go

M4 ring gauge 6g Go

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