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  • BSP

1) British Standard Pipe Parallel
British Pipe Standard fittings are amongst the most popular of all foreign threads in the world. These threads come in 2 versions: parallel (BSPP), and tapered (BSPT). The thread flank angle for both tapered and parallel British threads is 55°. NOTE: It is a common mistake to identify a BSPT (tapered) as an NPT. Remember that NPT threads have a 60° thread flank angle, and BSPT has a 55° angle (this can be verified with a thread gauge). Although BSP is a foreign thread, it isn't metric. This is why it comes in imperial sizes: 1/8, 1/4, 1/2, 3/4, and so on.
BSPP-tech

  • •Thread conforms to ISO 228-1
  • •Port conforms to ISO 1179
  • •Pitch & diameter measured in inches e.g. G1/4-19
  • •Parallel threads require o-ring, crush washer, gasket or metal to metal seal between connectinos for pressure tight connection
  • •Thread angle is 55°
  • Not interchangeable with SAE or NPT(F)
  •   BSPP Thread Specification
    (BSPP Indicator: G)
    Size Nominal Size (in) Thread Size (mm)
    2 1/8 9.728 - 28
    4 1/4 13.157 - 19
    6 3/8 16.662 - 19
    8 1/2 20.955 - 14
    10 5/8 22.911 - 14
    12 3/4 26.441 - 14
    14 7/8 30.201 - 14
    16 1 33.249 - 11
    18 1-1/8 37.897 - 11
    20 1-1/4 41.910 - 11
    22 1-3/8 44.323 - 11
    24 1-1/2 47.803 - 11
    28 1-3/4 53.746 - 11
    32 2 59.614 - 11
    Thread Size = Male Thread OD - Threads per Inch


    2) British Standard Pipe Tapered

    For tapered BSP threads, a seal is acquired via thread wedging with additional support from thread dope or Teflon® tape. It is possible for a male BSPT (tapered) to thread into a female BSPP (parallel), so long as the female thread is fixed and not swivel (this is because of the recessed cone seat on the BSPP end).

    You must find the I.D. to determine the threads per inch count for BSPT fittings. Simply obtain a caliper reading from inside the bore of the fitting. You can cross-reference the bore size on the following chart with thread pitch and threads per inch to find your desired size and its related specs.
    BSPT-tech

  • Thread conforms to ISO 7
  • Pitch and diameter are measured in inches, e.g. R3/8-19
  • Tapered thread profile seals by metal to metal intererence fit, usually requires sealing compound for pressure tight connection
  • Taper angle is 1° 47', the same as NPT(F)
  • Thread angle is 55°
  • Not interchangeable with NPT(F)

  • BSPT Thread Specification
    (BSPT Indicator: R)
    Nominal
    Size
    (in)
    Dash
    Size
    Outer
    Diameter
    (mm)
    Inner
    Diameter
    Male Thread
    (mm)
    Pitch
    (mm)
    Threads
    per
    Inch
    Pitch
    Diameter
    Thread
    Height
    (mm)
    Tap
    Drill
    Diameter
    (mm)
    Thread
    Crest
    Rounding
    1/16 01 7.723 6.561 0.907 28 7.142 0.581 6.40 0.125
    1/8 02 9.728 8.566 0.907 28 9.147 0.581 8.40 0.125
    1/4 04 13.157 11.445 1.337 19 12.301 0.856 11.20 0.184
    3/8 06 16.662 14.950 1.337 19 15.806 0.856 14.75 1.840
    1/2 08 20.955 18.631 1.814 14 19.793 1.162 18.25 0.249
    3/4 12 26.441 24.117 1.814 14 25.279 1.162 23.75 0.249
    1 16 33.249 30.291 2.309 11 31.770 1.479 30.00 0.317
    20 41.910 38.952 2.309 11 40.431 1.479 38.5 0.317
    24 47.803 44.845 2.309 11 46.324 1.479 44.5 0.317
    2 32 59.614 56.656 2.309 11 58.135 1.479 56.0 0.317
    Thread Size = Male Thread OD - Threads per Inch

    BSPT T.F.F.T.
    1/8-28 2 - 3
    1/4-19 2 - 3
    3/8-19 2 - 3
    1/2-14 2 - 3
    3/4-14 2 - 3
    1-11 1.5 - 2.5
    1¼-11 1.5 - 2.5
    1½-11 1.5 - 2.5
    2-1 1.5 - 2.5
    Assembly Turns From Finger Tight values
    for steel, stainless steel and brass fittings.
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