1" BSPT Thread
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1" BSPT Thread dimensions and 1 inch tapered thread specification
The 1" BSPT thread (British Standard Pipe Tapered, designated according to international standards as R 1" for male tapered threads and Rc 1" for female threads) is a standardized tapered pipe thread used in power hydraulic systems, pneumatics, gas installations, and industrial transmission lines. It is characterized by a taper ratio of 1:16 and a thread angle of 55°. Sealing in a 1" BSPT connection occurs directly on the thread turns through mechanical pressing of the male cone into the socket, which, combined with an appropriate sealant (e.g., PTFE tape, anaerobic adhesive, or hemp), guarantees complete leak-tightness under high operating pressure.
Application and technical characteristics of the 1" BSPT thread
The 1" BSPT size is commonly used in high-pressure installations with high medium flow rates. It is found in hydraulic pump bodies, valve blocks, manifolds, as well as in screw-in fittings (e.g., type AGR-K / C31) connecting flexible hydraulic hoses to stationary and mobile equipment.
- 11 TPI thread pitch: There are 11 turns per one inch of thread length (the thread pitch is approx. 2.309 mm).
- 55° thread angle: Consistent with the traditional British Whitworth standard for pipe threads.
- 1:16 tapered design: The external thread diameter increases along the axis towards the base, providing self-sealing during tightening.
- High pressure resistance: Allows for safe operation in oil and water installations with working pressures ranging from 160 to 350 bar (depending on the material version of the fitting).
- Compliance with standards: Compliant with international standards ISO 7-1, EN 10226-1, BS 21, and DIN 2999.
Identification and measurement of the 1" BSPT thread at the HYDRON store
To correctly identify a 1" BSPT thread using a caliper, you should measure the diameter on the threads. In the case of an external (male) thread, the diameter measured at the top of the cone is approx. 33.0 mm to 33.2 mm. The dedicated internal thread has a diameter measured inside the socket within the range of 30.3 – 30.8 mm. When measuring with a thread gauge, the pattern should indicate a pitch of 11G (11 turns per inch). For the construction and service of installations using 1" BSPT tapered connections, we recommend high-quality flexible hydraulic hoses, matching steel hose fittings, self-sealing test points and diagnostic test kits.
Technical specification
| Technical parameter | Value / Description |
|---|---|
| Standard designation | BSPT (British Standard Pipe Tapered) / R 1" (external) / Rc 1" (internal) |
| Nominal bore diameter (DN) | DN 25 (1 inch) |
| External diameter of male thread | 33.0 mm – 33.2 mm (measured with a caliper) |
| Internal diameter of female thread | 30.3 mm – 30.8 mm (measured with a caliper) |
| Number of turns per inch (pitch) | 11 TPI (pitch approx. 2.309 mm) |
| Thread angle | 55° |
| Taper ratio | 1:16 (taper angle 1°47') |
| Sealing method | On the tapered thread (requires use of PTFE sealant or adhesive) |
| Reference standards | ISO 7-1, EN 10226-1, BS 21, DIN 2999 |
Frequently Asked Questions (FAQ)
What are the exact dimensions of the 1" BSPT thread?
The 1" BSPT male external thread has an outer diameter measured with a caliper of approx. 33.0–33.2 mm. The female internal thread has an inner diameter of approx. 30.3–30.8 mm. The thread pitch is 11 turns per inch.
What is the difference between 1" BSPT and 1" BSPP (G 1") threads?
The 1" BSPT thread is a tapered (convergent) thread that seals on the thread turns. The 1" BSPP (G 1") thread is a cylindrical (straight) thread and requires sealing on the face of the seat (e.g., using an ED seal, copper washer, or O-ring).
How to correctly seal a connection with a 1" BSPT thread?
A BSPT tapered connection is sealed by tightening the turns. To ensure 100% leak-tightness under high pressure, apply Teflon tape (PTFE), hemp with sealing paste, or anaerobic hydraulic thread adhesive to the external thread.
Is the 1" BSPT thread compatible with the American 1" NPT thread?
No. Although both threads are tapered, the 1" BSPT thread has a 55° thread angle and a pitch of 11 turns per inch, while the 1" NPT thread has a 60° thread angle and a pitch of 11.5 turns per inch. Connecting them directly leads to thread damage and leaks.