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M7 6H Go NoGo internal thread gauge
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  • M7 6H Go NoGo internal thread gauge
Artykuły Techniczne

Thread plug gauge M7 6H

Artykuły Techniczne Artykuły Techniczne
0000003233
€16.18 tax inc.

Net price: €13.16

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Description

THREADM7x1
TOLERANCE6H
STANDARDISO 1502
MATERIALTool steel

Thread plug gauge M7 6H GO/NO-GO

Internal thread gauge according to PN-ISO 1502:1998

TECHNICAL DATA
Thread type ISO metric (M)
Thread size M7
Thread pitch 1 mm
Tolerance class 6H
Gauge type GO / NO-GO
Material Tool steel, hardened
Hardness 58-62 HRC
Standard PN-ISO 1502:1998
Manufacturer Varel
Construction of the M7-6H thread plug gauge: GO end, engraved handle, NO-GO end
1
GO end — longer thread with a full profile. It is screwed in by hand through the full length of the hole.
2
Handle engraved with M7-6H — the size and tolerance class of the hole being checked.
3
Red ring — identifies the NO-GO end.
4
NO-GO end — shorter thread with a truncated profile. It checks only the pitch diameter, so it is allowed to enter by 2 turns.

Thread plug gauge M7 6H provides the fastest check of a threaded hole — without a micrometer or calculations. The end GO must enter by hand along the full thread length, while the end NO-GO must stop after no more than 2 turns, counted when unscrewing. GO enters, NO-GO does not — the hole meets class 6H.

These are the most frequently inspected threads in the shop — bolt holes in housings, brackets and machine subassemblies. In series production, the gauge detects a dull tap faster than visual inspection or trying a random bolt. The 1 mm pitch is the coarse pitch for this diameter: the designation M7 without a specified pitch denotes this particular thread. For reference: the minor diameter of the thread M7 is 5.917 mm, while the gauge checks the pitch diameter, which is the dimension halfway up the thread profile.

Operating principle: GO / NO-GO

How to check an internal thread correctly

M7-6H thread plug gauge: GO end screwed in by hand through the full length of the hole
1
The GO end is screwed in by hand, without force, through the full length of the M7 x1 thread.
M7-6H thread plug gauge: NO-GO end stops in the hole after 2 turns
2
The NO-GO end stops after no more than 2 turns — turns are counted when unscrewing.
Inspection result with the M7-6H gauge: GO passed, NO-GO stopped, hole within class 6H
3
The GO end passed, the NO-GO end stopped — the hole is within class 6H.

Thread inspection in 3 steps

1 GO end (longer thread)

Screwing into the thread — must enter

2 NO-GO end (red)

Screwing into the thread — no more than 2 turns

✓ Acceptable thread

Tolerance: 6H OK

If the end GO enters, and the end NO-GO does not enter — the thread meets the requirements of class 6H according to PN-ISO 1502:1998

GO end (passes)

No color marking — it has a longer thread and GO marked on the handle. It checks minimum internal thread dimensions. It must screw in freely along the full thread length. If it does not enter — the thread is undersized (the workpiece requires rework).

NO-GO end

Marked with a red ring. Checks maximum thread dimensions. It must not screw in more than 2 threads, with turns counted when unscrewing the gauge, not when screwing it in. If it goes farther — the thread is too loose and the part does not meet the tolerance class. For a thread 3 turns long or shorter, the NO-GO end must not pass all the way through.

Thread plug gauge in a hole: GO enters, NO-GO stops — thread acceptable
✓ Thread acceptable — GO enters the full length, NO-GO stops.
Thread plug gauge: GO end does not enter the hole — thread too tight
✗ Thread too tight — GO does not enter the hole.
Thread plug gauge: NO-GO end enters too far — thread too loose
✗ Thread too loose — NO-GO enters more than 2 turns.

Tolerance class 6H for an M7x1 thread

Comparison of tolerance classes for an M7x1 internal thread

Comparison of classes 4H, 5H, 6H and 7H

Basic pitch diameter D2 for the thread M7 is 6.350 mm. In classes designated H, this is also the minimum dimension — the tolerance extends upward only.

ClassD2 nominal [mm]D2 permissible [mm]Tolerance zoneApplicationStatus
4H6.350 mm6.350 – 6.445 mm0.095 mmPrecision
5H6.350 mm6.350 – 6.468 mm0.118 mmClose
6H6.350 mm6.350 – 6.500 mm0.150 mmStandardTHIS PRODUCT
7H6.350 mm6.350 – 6.540 mm0.190 mmCoarse

The full range of class 6H for the thread M7 is 0.150 mm: from 6.350 to 6.500 mm. Class 6H corresponds to a typical nut and a standard machine tap — it is selected for class 6g bolts. Classes 4H and 5H reduce clearance where the thread guides a component; 7H leaves an allowance for electroplating. The values in the table refer to pitch diameter D2, not the tap drill diameter.

Set contents and storage

Set contents and gauge storage

INCLUDED:

✓ Thread plug gauge M7 6H GO/NO-GO
✓ Size marking on the plug

STORAGE:

✓ Store in a dry place, in its case
✓ Protect against dropping — impact damages the thread
✓ Apply rust-preventive oil periodically

Frequently asked questions

6H is the most commonly used internal thread tolerance class according to ISO 965-1. The digit 6 specifies the tolerance grade (zone width), and the letter H indicates the tolerance zone position (lower deviation = 0). Class 6H provides a standard fit with class 6g bolts.

The end GO (GO, with the longer thread) must enter freely along the full thread length. The end NO-GO (NO-GO, red) should not screw in more than 2 turns (counted when unscrewing). Both conditions must be met simultaneously for the thread to be considered acceptable according to PN-ISO 1502:1998.

Gauge wear is checked by periodic measurement at intervals based on usage intensity (ISO 1502, clause 7.2.1); the standard specifies neither the number of measurements nor a fixed interval. A worn gauge gives false positive results — the NO-GO end starts entering the thread. The gauge should be verified periodically using setting gauges.

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Thread plug gauge M7 6H

Thread plug gauge M7 6H

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