H — tolerance position
For a hole, H places the lower deviation at the basic-size zero line in the ISO limits-and-fits system.
Drawing input Nominal diameter and the full hole callout are required.Plain plug gauges for GO/NO-GO bore inspection
Custom GO/NO-GO plug gauges for rapid pass/fail verification of H7 precision holes.
Review GO / NO-GO selection notes
DECLARED SUPPLY RANGE
1–100 mm H7 HOLE CLASS
A limit decision, not a measured value
A plain plug gauge verifies whether a hole remains within two specified size limits. It is fast and repeatable for production acceptance, but it does not display the actual diameter or the amount of deviation.
Use without force
Clean the part and gauge, align them carefully and apply only normal handling pressure. The approved
inspection procedure defines the engagement rule; forcing either member can damage the gauge and
invalidate the decision.
Read the two limits correctly
- GO member
- Represents the hole's maximum-material boundary. It should enter as required by the approved procedure when the hole is acceptable.
- NO-GO member
- Represents the opposite size limit. It must not enter beyond the acceptance rule stated in the inspection procedure.
- Decision
- Accept only when both conditions are satisfied. Use a variable instrument when the actual diameter or process trend is required.
H7 belongs to the hole specification
The H7 callout defines the tolerance zone of the inspected internal feature. Gauge manufacturing limits are then calculated separately from the nominal diameter, workpiece limits and the selected gauge standard.
7 — tolerance grade
IT7 sets the tolerance width, and that width changes with the nominal-diameter step.
Not one fixed value An H7 tolerance cannot be converted to gauge sizes without the nominal diameter.Gauge limits
The GO and NO-GO members have their own manufacturing tolerances and applicable wear allowance.
Certificate check Confirm calculated limits, measured results, uncertainty and traceability before approval.Main features
- GO and NO-GO limits provide a fast pass/fail decision without a displayed measurement value
- H7 identifies the inspected hole tolerance class; it is not the manufacturing grade of the gauge
- Declared supply range from 1 mm to 100 mm, configured to nominal diameter
- Product hardness declaration HRC 60±2; actual compliance evidence requires certificate confirmation
- Declared conformity to current GB/T 1957-2006 for plain limit gauges
- Gauge limits, manufacturing tolerance and wear allowance are calculated for the ordered size
Applications
Application specifications
| Product type | Plain limit plug gauge for internal features |
|---|---|
| Inspection result | GO / NO-GO pass/fail decision; no numerical reading |
| Inspected hole class | H7 |
| Declared diameter range | 1–100 mm |
| Declared hardness | HRC 60±2 |
| Declared product standard | GB/T 1957-2006 |
| Standard status checked | Current; reaffirmed 28 December 2023 |
| Gauge limits | Calculated from nominal size, hole limits and governing gauge standard |
| Reference condition | 20 °C for dimensional verification; certificate procedure applies |
H7 is the workpiece-hole tolerance class, not a gauge accuracy grade. GB/T 1957-2006 is current and specifies at least 60 HRC for steel measuring faces; because the supplied product statement is HRC 60±2, request the actual hardness result and conformity evidence in the written quotation or certificate. ISO 1938-1:2026 is the current international reference for plain limit gauges, but ISO conformity is not claimed here.
Included
- One configured GO/NO-GO plain plug gauge set at the confirmed nominal size and H7 hole class
Configuration options
- Combined double-ended or separate GO and NO-GO members, subject to diameter and approved design
- Individual serial-number and size marking
- Protective storage case
- Calibration or inspection certificate with stated traceability
- Alternative documentation or reference-temperature requirements by written agreement
Frequently asked questions
What information is needed to specify a plain plug gauge?
Provide the nominal hole diameter, complete tolerance callout (for example, Ø20 H7), quantity, GO/NO-GO format, measured material and process, inspection rate, engagement length and any certificate, traceability, serial-marking or reference-temperature requirement.
Does a plain plug gauge show the actual hole size?
No. A plain plug gauge gives a fixed-limit pass/fail decision. Use a calibrated variable instrument when the actual diameter, deviation, process capability or trend data is required.
Can I buy it online?
Public prices and payment credentials are not configured. AccuTouch will confirm price, GST, configuration and delivery through a written quotation.
What does H7 mean on the component drawing?
H identifies the tolerance position for a hole and 7 identifies the IT tolerance grade. The allowable width changes with nominal diameter. H7 therefore describes the inspected hole, not the manufacturing accuracy grade of the gauge.
What is the correct GO/NO-GO acceptance result?
With clean, aligned surfaces and normal handling pressure, the GO member should enter as required by the approved engagement rule and the NO-GO member must not enter beyond its defined rule. Never force either member; both conditions must be satisfied for acceptance.
Can a plain plug gauge measure roundness, taper or the actual diameter?
It gives a limit decision and may respond to some combined size-and-form conditions, but it does not quantify diameter, roundness or taper. Use variable or form measurement when numerical results or process trends are required.
Why should the calibration certificate be specified?
The certificate should identify the calculated gauge limits, measured results, uncertainty, traceability, reference temperature and applicable standard. A catalogue claim alone does not demonstrate that the supplied gauge meets the limits for your specific nominal size and tolerance.
How is the declared HRC 60±2 hardness handled?
GB/T 1957-2006 specifies at least 60 HRC for steel measuring faces. Because a nominal HRC 60±2 range extends below that minimum, request the actual test result and the conformity acceptance criterion on the quotation or supplied certificate.
What is the delivery time?
Lead time is confirmed after the nominal diameter, tolerance, GO/NO-GO format, quantity, marking and certification requirements are approved. The written quotation or order acknowledgement gives the committed schedule.
How should the gauge be used, protected and stored?
Clean the gauge and component before use, avoid force and impact, and store the gauge dry in its protective case with suitable corrosion protection. Verify identification and calibration status before inspection, and follow the approved recalibration interval for the application.
Can one gauge inspect different diameters or tolerance classes?
A gauge is normally dedicated to one calculated set of workpiece limits. Use it for another drawing only when the resulting limits are identical and that use has been formally approved in the inspection plan.
Related engineering resources
Plan the complete measurement application
Use these guides, applications and tools to define the right gauging configuration.