Thread Plug Gauge and Ring Gauge

1.Introduction

Thread Plug Gauge and Ring Gauges are precision measurement tools used to inspect the dimensional accuracy of internal and external threads.They ensure proper fit,functionality,and interchangeability of threaded components in manufacturing.The two primary types are:

Thread Plug Gauge:Checks internal threads(e.g.,nuts,threaded holes).

Thread Ring Gauge:Inspects external threads(e.g.,bolts,studs).

These gauges typically come in Go/No-Go pairs to verify thread acceptance within specified tolerances.

2.Types and Design

(1)Thread Plug Gauge

Go Plug:Must fully thread into the part without force,confirming the minimum major diameter and pitch alignment.

No-Go Plug:Should not thread beyond 1.5–2 turns,ensuring the maximum pitch diameter is within limits.

Adjustable Plug Gauges:Allow recalibration(e.g.,Vermont Gage models)for extended use.

(2)Thread Ring Gauge

Go Ring:Must screw onto the external thread smoothly,validating the maximum major diameter.

No-Go Ring:Must not fit beyond 2 turns,checking the minimum pitch diameter.

Adjustable Ring Gauges:Feature a split design for fine-tuning(e.g.,Vermont Gage).

3.Standards and Specifications

Thread Standards:

Metric:ISO 1502(e.g.,M12×1.75,tolerance class 6H/6g).

Imperial:ASME B1.2(e.g.,1/2"-13UNC-2A/2B).

Pipe Threads:NPT,BSPP,BSPT.

Tolerance Classes:

External Threads:6g(general use),4h(tight tolerance).

Internal Threads:6H(standard),5H(high precision).

4.Material and Construction

Materials:Hardened tool steel(HRC 58–64),carbide,or stainless steel for corrosion resistance.

Calibration:NIST-traceable certificates available;some gauges include master setting plugs for calibration.

Surface Finish:Ground and lapped to≤0.05µm roughness for accuracy.

5.Applications

Automotive/Aerospace:Critical for engine components,landing gear,and hydraulic systems.

Oil&Gas:Ensures pressure-tight connections in pipelines and valves.

General Manufacturing:QC checks for screws,fasteners,and machined parts.

6.Selection and Maintenance

Choosing a Gauge:Match thread type(metric/imperial),pitch,and tolerance class.

Calibration:Recalibrate annually or per usage frequency(ISO 17025 standards).

Storage:Keep in protective cases to prevent wear or damage.

7.Purchasing Options

Standard Gauges:

Plug gauges:$50–$300(e.g.,M10×1.5 Go/No-Go set).

Ring gauges:$100–$500(e.g.,1"-8UNF-2A adjustable ring).

Custom Gauges:OEM suppliers offer tailored solutions for non-standard threads.

8.Key Brands

Thread Plug Gauges:Mitutoyo,Starrett,Vermont Gage.

Thread Ring Gauges:Meyer Gage,Thread Check Inc.,Pratt&Whitney.

Conclusion

Thread plug and ring gauges are indispensable for maintaining thread quality in precision engineering.Proper selection,calibration,and handling ensure compliance with international standards and reduce production defects.For specialized needs(e.g.,micro-threads or left-hand threads),consult gauge manufacturers for custom solutions.