ISO-7 vs. BS-21 British Standard Pipe Taper

ISO-7 vs. BS-21 British Standard Pipe Taper

What Is The Same?
The product threads in ISO-7 and BS-21 and EN-10226 are identical and fully interchangeable.

What Is Different?
The screw thread gage design is different. Here is a listing of the available gages for each specification:

BS-21:1985; Page 10; Appendix A. Recommended gauging systems for joining threads.
Paragraph A.2. System A
- Figure 7. Rc-series Tapered Full-Form Screw Thread Plug Gage
- Figure 8. R-series Tapered Full-Form Screw Thread Ring Gage
Paragraph A.3. System B
- Figure 9. Rc-series Tapered Full-Form Screw Plug Gage
- Figure 10. R-series Tapered Full-Form Screw Ring Gauge
- Figure 11.0 Rc-series Tapered Plain Plug Gauge
- Figure 12. R-series Tapered Plain Ring Gauge

ISO-7-2:2000; Page 29; and EN 10226-3:2005 Page 34; Annex A Summary of gauges; Figure A.1:
- Gauge No. 1 - Taper Full Form Threaded Plug Gauge
- Gauge No. 2 - Taper Full Form Threaded Plug Gauge with Relief
- Gauge No. 3 - Parallel Full Form Threaded Ring Gauge
- Gauge No. 4 - Taper Plain Ring Gauge
- Gauge No. 5 - Taper Modified Thread Form Check Plug Gauge
- Gauge No. 6 - Parallel Modified Thread Form Check Ring Gauge

Suggestion on Which Gages to Use
If the requirement for using gages is internal to your company; use either standard.
If the requirement for using gages is enforced by your customer; use the specification which they identify.

Disclaimer:
This data is provided for general information only. The intention is to provide accurate information; regardless; errors may exist in the supplied information. If accuracy is critical, base your final decisions on the data provided in the root documents: BS-21:1985; ISO 7-2:2000; and EN 10226-3:2005; which are a copyrighted documents.
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Comments:
Original Posting: 1/2/2008
Last Revision: 1/28/2015
If you have some old documentation which will make this history more complete and you are willing to share; please email the document(s) to me at: office@gagecrib.com.