Thread Gauges | Plug | Ring | GO/NO-GO
Precision Thread Gauges for Internal and External Thread Inspection
GageTools manufactures GO/NO-GO thread plug gauges, thread ring gauges, pipe thread gauges and custom thread inspection tools for production QC, incoming inspection and supplier approval.
Product Range
Thread Gauges We Manufacture
Choose the right gauge type based on the thread you need to inspect. Internal threads usually require plug gauges; external threads usually require ring gauges.
Thread Plug Gauges
GO/NO-GO plug gauges for checking internal threads in nuts, tapped holes, machined parts and assemblies.
Thread Ring Gauges
GO/NO-GO ring gauges for checking external threads on bolts, shafts, fittings and threaded components.
Pipe Thread Gauges
BSPP, BSPT, NPT and NPTF plug and ring gauges, including taper pipe thread gauge sets.
Metric Thread Gauges
ISO metric gauges from small precision sizes to large made-to-order gauges, with common 6H/6g support.
Unified Thread Gauges
UNC, UNF, UNEF and special UN gauges to ANSI/ASME requirements for US thread inspection.
Custom Thread Gauges
Special pitch, non-standard tolerance, buyer drawing, private label marking and custom packaging are available.
How It Works
GO/NO-GO Gauging Principle
A thread is accepted when the GO gauge passes correctly and the NO-GO gauge does not pass beyond the allowed limit. This functional method helps verify size, pitch, lead and thread form in production inspection.
The GO member should enter fully by hand pressure only. It verifies the maximum material condition.
The NO-GO member should not engage beyond the allowed number of turns, commonly not more than two turns.
Quality Documents
Inspection Report and Calibration Certificate Available
Thread gauges can be supplied with inspection records and calibration documentation for incoming QC, supplier approval and controlled manufacturing environments.
- Thread size, tolerance class and gauge serial number
- Pitch diameter and critical measured values where required
- Hardness, surface finish and marking inspection
- NIST-traceable calibration route available on request
- Custom certificate format for OEM or distributor orders
Common Sizes
Metric Thread Gauge Size Reference
Below are common metric coarse thread sizes. We also manufacture fine pitch, left-hand, oversize, undersize and special drawing gauges.
| Thread Size | Pitch mm | Major Dia mm | Common Tolerance | Gauge Type | Availability | RFQ |
|---|---|---|---|---|---|---|
| M3 x 0.5 | 0.50 | 3.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M4 x 0.7 | 0.70 | 4.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M5 x 0.8 | 0.80 | 5.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M6 x 1.0 | 1.00 | 6.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M8 x 1.25 | 1.25 | 8.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M10 x 1.5 | 1.50 | 10.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M12 x 1.75 | 1.75 | 12.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M16 x 2.0 | 2.00 | 16.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M20 x 2.5 | 2.50 | 20.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M24 x 3.0 | 3.00 | 24.00 | 6H / 6g | Plug or ring | Common stock | Quote |
| M30 x 3.5 | 3.50 | 30.00 | 6H / 6g | Plug or ring | Made to order | Quote |
| M42 x 4.5 | 4.50 | 42.00 | 6H / 6g | Plug or ring | Made to order | Quote |
| M100 x 6.0 | 6.00 | 100.00 | Custom | Plug or ring | Made to order | Quote |
RFQ Checklist
Information Needed for a Fast Quote
Thread Callout
Send size and pitch, such as M12 x 1.75, 1/2-13 UNC, G1/4, 1/8 NPT or your drawing number.
Gauge Type
Tell us if you need plug gauge, ring gauge, taper pipe gauge, master gauge or complete GO/NO-GO set.
Documents
Confirm whether you need calibration certificate, inspection report, material certificate or custom marking.
Gauge Types
Thread Gauge Types at a Glance
Each thread gauge type checks a different feature. Use the table to find the gauge for your part, then follow the link for sizes and ordering details. All types are available as GO/NO-GO pairs or as individual members.
| Gauge type | Checks | Typical standards | Guide |
|---|---|---|---|
| Thread plug gauge | Internal threads: tapped holes, nuts | ISO 1502, ASME B1.2 | Thread plug gauges |
| Thread ring gauge | External threads: bolts, studs, shafts | ISO 1502, ASME B1.2 | Thread ring gauges |
| Setting plug | Size of adjustable ring gauges | ASME B1.2 | Setting plug guide |
| Taper pipe gauge | Stand-off of NPT, NPTF and BSPT threads | ASME B1.20.1, B1.20.3, ISO 7-2 | Pipe thread gauges |
| Acme / trapezoidal gauge | Power and lead screw threads | ASME B1.5, ISO 2903 | Trapezoidal gauge guide |
Standards
Thread Standards We Cover
| Standard family | Designation example | Gauge types supplied |
|---|---|---|
| ISO metric coarse and fine | M8×1.25-6H, M16×1.5-6g | Plug and ring, GO/NO-GO |
| Unified inch | 1/4-20 UNC-2B, 3/8-24 UNF-2A, UNEF | Plug, adjustable ring, setting plugs |
| American taper pipe | 1/2-14 NPT, NPTF | L1 plugs and rings |
| British pipe | G 1/2 (BSPP), R 1/2 / Rc 1/2 (BSPT) | Parallel plug and ring, taper plug and ring |
| Trapezoidal and Acme | Tr20×4-7H, 1-5 Acme-2G | Plug and ring, often made to order |
| MJ / UNJ | MJ10×1.25-4h6h, UNJF | Made from drawing on request |
Metric and unified gauges are the bulk of our output and most common sizes are held in stock. Pipe thread gauges cover both sealing threads (NPT, NPTF, BSPT) and parallel fastening threads (BSPP). Trapezoidal, Acme and MJ/UNJ gauges are usually manufactured to order because pitch, class and length of engagement vary by application.
If your drawing uses a standard not listed here, send it with your RFQ and we will confirm whether we can manufacture the gauge before quoting.
Selection
How to Choose a Thread Gauge in 5 Steps
- Identify the thread. Internal or external, size, pitch or TPI, and thread series from the drawing.
- Confirm the tolerance class. For example 6H, 6g, 2B or 3A. The class decides the gauge limits.
- Pick the gauge type. Plug for internal threads, ring for external, taper gauge for pipe threads.
- Decide the set format. Double-ended plug, separate members, ring pair, or ring pair with setting plugs.
- State documentation needs. Inspection report, ISO/IEC 17025 calibration certificate on request, marking and packaging.
If you are replacing an existing gauge, a clear photo of its marking and the case label often answers steps 1 to 4. If you have no drawing, send a sample part or the mating component and we will advise on the gauge specification.
Standard sizes ship from stock within 72 hours; custom gauges take 10–15 working days. MOQ is 1 piece.
Industries
Industries That Use Our Thread Gauges
- Fastener manufacturers: bolts, nuts, screws and studs in metric and inch sizes.
- Automotive parts suppliers: engine, brake and chassis components with tapped holes.
- Hydraulic and pneumatic fittings: NPT, BSPP and BSPT ports and connectors.
- Valve and pump makers: pipe threads and trapezoidal stem threads.
- CNC machining shops: in-process checks on turned and milled threads.
- Machinery and equipment builders: lead screws, adjusting screws and assembly threads.
- Importers and distributors: incoming inspection of threaded parts sourced from multiple suppliers.
Across these industries the need is the same: a reliable accept/reject decision at the machine or at goods-in, without sending every part to a measuring lab. GO/NO-GO gauges give operators that decision in seconds, and a matched set in each location keeps results consistent between shifts, plants and suppliers.
Direct Supply
Why Buy Thread Gauges from a Manufacturer
Buying direct from the factory that grinds the gauge changes what you can control:
- Technical answers from the source. Questions about class, plating allowance or a non-standard pitch go to the people who make the gauge.
- Custom work. Gauges made from your drawing, including special pitches and left-hand threads.
- Consistent replacements. Single GO or NO-GO members matched to your existing sets.
- Clear lead times. Stock sizes within 72 hours, custom gauges in 10–15 working days, RFQ reply within 24 hours.
- Small orders accepted. MOQ is 1 piece, so a single replacement gauge is quoted the same way as a full set.
A trading company can be useful for consolidating unrelated tools, but it adds a step between your question and the production floor. For thread gauges, where one wrong letter in the class makes the gauge useless, that step matters.
For the practical differences, read thread gauge manufacturer vs trader.
FAQ
Thread Gauge Questions
What is the difference between a thread gauge and a thread pitch gauge?
A thread pitch gauge is a set of leaves used to identify pitch or TPI. A GO/NO-GO thread gauge checks whether a thread is within its tolerance limits, mainly pitch diameter. Pitch gauges identify a thread; plug and ring gauges accept or reject it. We manufacture GO/NO-GO plug and ring gauges.
Which thread gauge do I need for a tapped hole?
A tapped hole is an internal thread, so you need a thread plug gauge. Give us the size, pitch or TPI and class, for example M10×1.5-6H or 3/8-16 UNC-2B. Most buyers order a double-ended GO/NO-GO plug. For blind holes, also tell us the usable thread depth.
Can you supply thread gauges for both metric and inch threads?
Yes. We manufacture ISO metric gauges to ISO 1502 and unified inch gauges (UNC, UNF, UNEF) to ASME B1.2, plus NPT, NPTF and BSP pipe thread gauges. Mixed orders covering several standards can be quoted together on one RFQ, with a single reply within 24 hours.
How do I get a quote for thread gauges?
Send the thread designation, gauge type, quantity and any certificate requirements by RFQ form or WhatsApp. A drawing or a photo of an existing gauge helps for custom or replacement orders. We reply within 24 hours with price, lead time and documentation. There is no minimum order beyond 1 piece.
Get a Quote
Request Thread Gauge Price and Lead Time
Send your thread specification or drawing. We will reply with gauge type, price, lead time and document options.
Quick Inquiry Links
Use these buttons instead of a fake form. They open real contact channels with a prepared message.