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British Standard Cycle Threads

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British Standard Cycle is a British Imperial screw thread standard made for bicycle and motorcycle applications.

British Standard Cycle Threads

Outside Diameter


1/4 26 0.0385 0.250 0.209
5/16 26 0.0385 0.3125 0.272
3/8 26 0.0385 0.3750 0.334
7/16 26 0.0385 0.4375 0.397
1/2 26 0.0385 0.5000 0.459
9/16 26 0.0385 0.5625 0.522
5/8 26 0.0385 0.6250 0.584
11/16 26 0.0385 0.6875 0.647
3/4 26 0.0385 0.7500 0.709
1 26 0.0385 1 0.959
1 3/8 24 0.0417 1.625 1.326
  • TPI = threads per inch
  • the thread angle is 60 degrees

The fine pitch allows high torque settings and is resistant to vibrations.

Note that the most commonly used bottom bracket thread today is 1 3/8" x 24 TPI.

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Related Topics


Thread data - metric, unified, ACME and others.

Related Documents

ANSI B1.20.1 - NPS - American National Standard Straight Pipe Threads

NPS pressure tight straight pipe threads with lubricant or sealer.

ANSI B1.20.1 - NPT - American National Standard Taper Pipe Threads

NPT and NPTF pipe threads - dimensions according ANSI/ASME B1.20.1/3.

British Standard Brass Threads

British Brass Thread is an imperial unit based screw thread.

ISO 228 - Pipe Threads where Pressure Tight Joints are not made on the Threads

Requirements for thread form, dimensions, tolerances and designation for fastening pipe threads, thread sizes.

ISO 2901 - Metric Trapezoidal Screw Threads

Dimensions of ISO metric trapezoidal screw threads.

ISO 7 - Pipe Threads where Pressure-tight Joints are made on the Threads

Pressure-tight joints made on the pipe threads.

Piping Thread Standards

Applied threaded standards used for piping connections.

Threads commonly used in Piping

Piping thread standards.

Whitworth Pipe Threads

BSPP (G) - British Standard Pipe Parallel and BSPT (R/Rp) – British Standard Tapered Pipe for pipes and tapered threads - G/R/Rp.

Withworth Threads - Taps and Drill Sizes

Taps and drill sizes used for Whitworth - ISO 7 and ISO 228 threads.

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