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British Thread Gages – BSP Gages – BS EN ISO 228

G Series - Formally known as BSPF
The BSPP Thread Gages conform to to BS EN ISO 228-1 Parts and -2 for Gages. The standard year is 2003.


Screw Thread Plug Gages are to a standard class of fit. British Thread Gages

British BSP Thread Ring Gages

Screw Thread Ring Gages are available in Class A and Class B

Class A on G Series rings is more common and considered standard. Class B only refers to rings, there is no class B on screw plugs

The go thread ring gauge is a class A only.Class B does not exist but you may get inquiries asking for a Class B go ring in which case we will mark the Class A as a class B.

The difference is only on the No go ring. Class A is a tighter tolerance than a Class B, The tolerance on a class B is twice that of the Class A.

In March 2003 the British Standards Institute withdrew BS-2799 and replaced it with ISO-228 ( technically BS-EN-ISO-228 )

Full Form British Thread Gages sold by Thread Check Inc are full form gages traceable to U.K.A.S


Gagemaker Functional Thread Gages for large diameter thread inspection

The Gagemaker functional thread gage inspection equipment is ideal for large diameter internal and external thread inspection. The measuring equipment is relatively low cost, extremely versatile and readily available compared to Fixed limit thread ring and thread plug gages

Functional thread size gages inspect the effects of all thread element variations and report deviations (functional size).The gages use matched sets of precision ground thread rolls that seat in the threads during inspection to ensure accuracy. Each set of thread rolls is designed to ANSI specifications to measure unlimited diameters for a specific thread form. Common pitches ranging from 4 TPI to 20 TPI of the UN Series, ACME, and Stub ACME, and 1.5mm to 4 mm of the ISO Metric thread rolls are in stock. Whitworth and 7° X 45° Buttress thread rolls are available with a fast lead time. Custom thread rolls are priced on request.

The PG-6000 Series gages inspect diameters of internal threads. The RG-7000 Series gages measure diameters of external threads.

Special thread forms are priced upon request. All thread rolls are sold separately in matching sets.


Measures internal or external threads for a range of diameters
Uses interchangeable thread rolls for measurement of different thread forms.
Replaces conventional ring and plug gages by providing actual diameter readings.
Provides functional measurement by inspecting the effects of thread element variations such as: lead, taper, thread height and pitch diameter.
Eliminates unnecessary damage to threads caused by ring and plug gages.
Durable construction allows use in a manufacturing or field environment.
Requires presetting using basic gage blocks, micrometers, or Gagemaker’s MIC TRAC measurement center.