What does G (BSP) mean according to DIN ISO 228?

G stands for British Standard Pipe Parallel (BSPP) thread, a parallel pipe thread according to DIN ISO 228 with a 55° Whitworth profile. The threads are measured in inches and do not provide sealing via the thread itself, but through gaskets or O-rings at the sealing face.

How is a BSP thread different from a metric thread?

Metric threads (e.g. M10 × 1.5) are measured in millimetres and have a 60° flank angle. BSP threads (e.g. G 1" × 11) use a 55° Whitworth angle and are measured in inches. BSP threads are common in pipework and hydraulic applications, whereas metric threads are used in general mechanical assemblies.

How does a GO/NO-GO plug gauge work?

The plug gauge has two ends: the GO side checks if the internal thread meets the minimum tolerance and should fit easily. The NO-GO side checks the maximum limit and should not enter more than two turns. This method quickly confirms thread accuracy without complex measurement tools.

What is the purpose of the red ring on the gauge?

The red ring clearly marks the NO-GO (reject) side of the gauge, preventing confusion during inspection. It indicates the side that must not fit more than two turns.

What is a factory calibration certificate?

A factory calibration certificate is an official document issued by VÖLKEL upon request. The gauge is calibrated at an independent measurement laboratory according to relevant standards (DIN, ISO, ANSI) using IAC thread scanners.

Why is 20 °C the reference temperature?

Thread tolerances are standardised for measurements taken at 20 °C. Deviations in temperature can cause expansion or contraction of materials, which affects accuracy.

What does G (BSP) mean according to DIN ISO 228?

G stands for British Standard Pipe Parallel (BSPP) thread, a parallel pipe thread according to DIN ISO 228 with a 55° Whitworth profile. The threads are measured in inches and do not provide sealing via the thread itself, but through gaskets or O-rings at the sealing face.

How is a BSP thread different from a metric thread?

Metric threads (e.g. M10 × 1.5) are measured in millimetres and have a 60° flank angle. BSP threads (e.g. G 1" × 11) use a 55° Whitworth angle and are measured in inches. BSP threads are common in pipework and hydraulic applications, whereas metric threads are used in general mechanical assemblies.

How does a GO/NO-GO plug gauge work?

The plug gauge has two ends: the GO side checks if the internal thread meets the minimum tolerance and should fit easily. The NO-GO side checks the maximum limit and should not enter more than two turns. This method quickly confirms thread accuracy without complex measurement tools.

What is the purpose of the red ring on the gauge?

The red ring clearly marks the NO-GO (reject) side of the gauge, preventing confusion during inspection. It indicates the side that must not fit more than two turns.

What is a factory calibration certificate?

A factory calibration certificate is an official document issued by VÖLKEL upon request. The gauge is calibrated at an independent measurement laboratory according to relevant standards (DIN, ISO, ANSI) using IAC thread scanners.

Why is 20 °C the reference temperature?

Thread tolerances are standardised for measurements taken at 20 °C. Deviations in temperature can cause expansion or contraction of materials, which affects accuracy.

VÖLKEL precision thread plug gauge G (BSP) with red marking, for accurate inspection of British Standard Pipe threads.

G (BSP) Pipe-thread

Precision Thread Plug Gauge - G (BSP) 1" x 11

Name: VÖLKEL Precision Thread Plug Gauge – G (BSP) 1" × 11 – DIN ISO 228
Brand: VÖLKEL
SKU: 16135
Availability: InStock

Item no. 16135

€89.00

in stock - more than 10 pieces available

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The prices are in Euro plus VAT and shipping, insurance and packaging costs.

Application

VÖLKEL Precision Thread Plug Gauge – G (BSP) 1" × 11 – DIN ISO 228

The VÖLKEL Precision Thread Plug Gauge G (BSP) 1" × 11 is your reliable and precise instrument for inspecting British Standard Pipe Parallel threads. Whether you’re in quality assurance, production, or maintenance, this GO/NO-GO gauge provides a fast and clear assessment of thread accuracy in accordance with DIN ISO 228.

The plug gauge combines two essential functions in one tool: The GO end must screw smoothly into the internal thread by hand, proving that the minimum dimension is within tolerance. The NO-GO end, marked with a red ring, must not enter more than two turns – ensuring the upper limit of tolerance isn’t exceeded. This simple test guarantees reliable results without requiring advanced metrology equipment.

BSP threads (British Standard Pipe) are commonly used in fluid and pneumatic systems. They differ from metric threads by their 55° Whitworth angle and inch-based sizes. While metric threads often seal along the flanks, BSPP threads (G type) seal at the face, typically using washers or O-rings. Ensuring the thread dimensions are correct is crucial for leak-free connections – and that’s where this precision gauge delivers consistent accuracy.

Each gauge is manufactured to the highest standards of dimensional stability. On request, VÖLKEL provides a factory calibration certificate, confirming compliance with the required international standards and traceability through independent measurement using IAC thread scanners.

Applications & Benefits

Accurate GO/NO-GO inspection for G (BSPP) internal threads
Complies with DIN ISO 228 for parallel pipe threads
Robust tool for production, inspection and quality control
Red ring marking for easy NO-GO identification
Reference temperature 20 °C for precise testing
Factory calibration certificate available on request

Technical Data

Product	VÖLKEL Precision Thread Plug Gauge
Thread type	G (BSPP) – British Standard Pipe Parallel, 55° Whitworth profile
Size	1" × 11 threads per inch
Standard	DIN ISO 228
Marking	NO-GO end with red ring
Reference temperature	20 °C
EAN	4022835161356
Article number	16135

Step-by-Step Instructions

Clean the thread: Remove dirt, chips and lubricants before inspection.
Insert GO end: Screw in the GO side smoothly by hand – if it binds, the thread is undersized.
Test NO-GO end: Insert the red-marked NO-GO side – it should not go more than two turns.
Compare results: Verify compliance with DIN ISO 228 tolerances.
Record results: Note inspection data, temperature, and calibration details for traceability.

FAQ

What is the difference between BSP and metric threads?
BSP threads are inch-based and have a 55° flank angle, while metric threads are measured in millimetres with a 60° angle. BSP threads are used in pipe and hydraulic systems; metric threads are used in general mechanical applications.

Can I use this gauge for BSPT (tapered) threads?
No, this gauge is designed for parallel BSPP (G-type) threads only. Tapered BSPT threads require a different plug gauge type.

How often should I recalibrate the gauge?
Depending on frequency of use, recalibration every 12–24 months is recommended for reliable accuracy.

What happens if the NO-GO end goes in more than two turns?
The thread is oversized and out of tolerance. This usually indicates tool wear or incorrect drilling dimensions.

Can I request a calibration certificate?
Yes. VÖLKEL offers a factory calibration certificate on request. Calibration is performed independently according to DIN, ISO and ANSI standards.

Want to learn more about thread gauges or the difference between BSP and metric threads? Get in touch via our contact form.

Additional information

Type of thread	Pipe thread
Standard	DIN ISO 228
Size	G (BSP) 1" x 11
EAN	4022835161356
Item number	16135
Gauge dimension	DIN EN ISO 228-2
Thread standard	DIN ISO 228