Coventry Gauge

OTHER THREAD FORMS AND SPECIFICATIONS

Coventry Gauge have a comprehensive library of thread

gauge standards. We will be pleased to advise on the correct

specification for your application.

Shown here are some of the more regularly used thread forms which are gauged using our products, all available on short lead times. The thread proportions are shown for guidance and we should be consulted for detailed information.
Thread Gauges to Japanese (JIS) specification
The JIS system is rather different to BS and ANSI. Some of the main specifications are summarised here.
JIS-B-0251 Metric coarse pitch series
JIS-B-0252 Metric fine pitch series
JIS-B-0253 Pipe threads for pressure tight joints
JIS-B-0254 Pipe threads for non pressure tight joints
JIS-B-0254 Unified threads coarse pitch series
JIS-B-0255 Unified threads fine pitch series

Multi-Start Gauges
Plug and ring gauges for testing multi-start threads, within the range of practicality, can be supplied.
Please submit details of your application to our technical department for evaluation.

Wire Insert Gauges
Screw plug gauges are available for testing pre-insert tapped holes for helicoil inserts and wire inserts.
When ordering gauges for pre-insert threads, it is important to state the type of insert to be fitted i.e. Helicoil inserts to Armstrong data sheets, or wire inserts to British Standard specifications.

It should be noted that the gauging philosophy of BS, ANSI

and JIS can be quite different so the required specification

should always be clearly stated.

MJ thread: BS 6293 / ISO 5855
Controlled root radius, for aerospace applications.
External threads are designated 4h/6h
Internal threads < Ø 5mm 4H/6H
> Ø 5mm 4H/5H
UNJ thread: BS 4084
Controlled root radius, for aerospace applications.
External threads are designated 3A
Internal threads are designated 3B

MJ: BS 6293 and UNJ: BS4084