BRITISH & METRIC FLUID CONVEYING PRODUCTS

Thread Reference Charts
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British Standard Pipe(BSPP, BSPF) Thread Form
  • r = Basic Radius = * 137329 p
  • h = Basic Depth of Thread = *640327 p
  • p = Pitch = 1/t.p.i. (Threads per Inch)
  • ISO 228, DIN 259, BS2779, JIS B0202
  • In Japan this thread is known as (PF)
  • Use prefix G for parallel thread. Example: G1/2
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DASH SIZE NOMINAL
THREAD SIZE (T.P.I.)
BASIC DEPTH OF
THREAD (h) (in.)
BASIC MAJOR
DIA. (in.)
BASIC EFFECTIVE
DIA. (in.)
BASIC MINOR
DIA. (in.)
RECOMMENDED TAP
DRILL SIZE
SIZE RP (mm) Size G (mm)
-1 1/16-28 .0229 .304 .2812 .2583 6.60 6.80
-2 1/8-28 .0229 .383 .3601 .3372 8.60 8.80
-4 1/4-19 .0337 .518 .4843 .4506 11.50 11.80
-6 3/8-19 .0337 .656 .6223 .5886 15.00 15.25
-8 1/2-14 .0457 .825 .7793 .7336 18.50 19.00
-10 5/8-14 .0457 .902 .8563 .8106 - 21.00
-12 3/4-14 .0457 1.041 .9953 .9496 24.00 24.50
-14 7/8-14 .0457 1.189 1.1433 1.0976 - 23.25
-16 1-11 .0582 1.309 1.2508 1.1926 30.25 30.75
-20 1 1/4-11 .0582 1.650 1.5918 1.5336 39.00 39.50
-24 1 1/2-11 .0582 1.882 1.8238 1.7656 45.00 45.00
-28 1 3/4-11 .0582 2.116 2.0578 1.9996 - 51.00
-32 2-11 .0582 2.347 2.2888 2.2306 56.50 57.00
-36 2 1/4-11 .0582 2.587 2.5288 2.4706 No Sizes of B.S.
(British
Standard)
drills are
recommended
in B.S. 1157:1975
for this range
-40 2 1/2-11 .0582 2.960 2.9018 2.8436
-44 2 3/4-11 .0582 3.210 3.1518 3.0936
-48 3-11 .0582 3.460 3.4018 3.3436
-52 3 1/4-11 .0582 3.700 3.6418 3.5836
-56 3 1/2-11 .0582 3.950 3.8918 3.8336
-60 3 3/4-11 .0582 4.200 4.1418 4.0836
-64 4-11 .0582 4.450 4.3918 4.3336
Tube Size (mm) AL Series LL Series L Series S Series A Series AG Series DIN 7631 60 degree cone
4 M 8 X 0.75 M 8 X 1.0 ---- ---- M 10 X 1.5 ---- M 12 X 1.5
6 M 10 X 1.0 M 10 X 1.0 M 12 X 1.5 M 14 X 1.5 M 12 X 1.5 ---- M 14 X 1.5
8 M 12 X 1.0 M 12 X 1.0 M 14 X 1.5 M 16 X 1.5 M 14 X 1.5 ---- M 16 X 1.5
10 M 14 X 1.0 M 14 X 1.0 M 16 X 1.5 M 18 X 1.5 M 16 X 1.5 ---- M 18 X 1.5
12 M 16 X 1.0 M 16 X 1.0 M 18 X 1.5 M 20 X 1.5 M 18 X 1.5 ---- M 22 X 1.5
13 ---- ---- ---- ---- ---- M 20 X 1.5 ----
14 M 18 X 1.0 ---- ---- M 22 X 1.5 M 20 X 1.5 ---- ----
15 M 20 X 1.0 ---- M 22 X 1.5 ---- M 22 X 1.5 ---- ----
16 M 22 X 1.0 ---- ---- M 24 X 1.5 M 24 X 1.5 ---- M 26 X 1.5
17 ---- ---- ---- ---- ---- M 24 X 1.5 ----
18 M 24 X 1.0 ---- M 26 X 1.5 ---- M 27 X 1.5 ---- ----
20 M 25 X 1.0 ---- ---- M 30 X 2.0 M 27 X 1.5 ---- M 30 X 1.5
21 ---- ---- ---- ---- ---- M 30 X 1.5 ----
22 ---- ---- M 30 X 2.0 ---- M 30 X 1.5 ---- ----
25 ---- ---- ---- M 36 X 2.0 M 33 X 1.5 ---- M 38 X 1.5
27 ---- ---- ---- ---- ---- M 36 X 1.5 ----
28 ---- ---- M 36 X 2.0 ---- M 36 X 1.5 ---- ----
30 ---- ---- ---- M 42 X 2.0 M 39 X 1.5 ---- ----
32 ---- ---- ---- ---- ---- ---- M 45 X 1.5
33 ---- ---- ---- ---- ---- M 45 X 1.5 ----
35 ---- ---- M 45 X 2.0 ---- M 45 X 1.5 ---- ----
38 ---- ---- ---- M 52 X 2.0 M 48 X 1.5 ---- ----
40 ---- ---- ---- ---- M 52 X 1.5 ---- M 52 X 1.5
42 ---- ---- M 52 X 2.0 ---- ---- M 52 X 1.5 ----
45 ---- ---- ---- ---- M 54 X 2.0 ---- ----
48 ---- ---- ---- ---- M 58 X 2.0 ---- ----
49 ---- ---- ---- ---- ---- M 58 X 2.0 ----
American National Pipe Taper (NPT) Thread Form
  • h = Basic Depth of Thread = *8 p
  • p = Pitch = 1/t.p.i. (Threads per Inch)
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Dash Size Nominal Thread Size - t.p.i. Basic depth of thread (h) (in.) Outside dia. of pipe (in.) Effective diameter at small end of external thread (in.) Basic Minor Dia. (in.) Recommended tap drill size (mm)
-1 1/16 - 27 .0296 .3125 .2712 .2812 6.30
-2 1/8 - 27 .0296 .405 .3635 .3736 8.70
-4 1/4 - 18 .0444 .540 .4774 .4916 11.10
-6 3/8 - 18 .0444 .675 .6120 .6270 14.50
-8 1/2 - 14 .0571 .840 .7584 .7784 18.00
-12 3/4 - 14 .0571 1.050 .9677 .9889 23.25
-16 1 - 11-1/2 .0696 1.315 1.2136 1.2386 29.00
-20 1 1/4 - 11-1/2 .0696 1.660 1.5571 1.5834 38.00
-24 1 1/2 - 11-1/2 .0696 1.900 1.7961 1.8223 44.00
-32 2 - 11-1/2 .0696 2.375 2.2690 2.2963 56.00
-40 2 1/2 - 8 .1000 2.875 2.7195 2.7622 67.00
Dash Size Nominal Size Threads per In. Male Thread O.D. Female Thread I.D.
-4 7/16 20 7/16 25/64
-5 1/2 20 1/2 29/64
-6 9/16 18 9/16 1/2
-8 3/4 16 3/4 11/16
-10 7/8 14 7/8 13/16
-12 1-1/16 12 1-1/16 31/32
-16 1-5/16 12 1-5/16 1-15/64
-20 1-5/8 12 1-5/8 1-35/64
-24 1-7/8 12 1-7/8 1-51/64
-32 2-1/2 12 2-1/2 2-27/64
Dash Size Nominal Size Threads per In. Male Thread O.D. Female Thread I.D.
-4 7/16 20 7/16 25/64
-5 1/2 20 1/2 29/64
-6 9/16 18 9/16 1/2
-8 3/4 16 3/4 11/16
-10 7/8 14 7/8 13/16
-12 1-1/16 12 1-1/16 1-63/64
-16 1-5/16 12 1-5/16 1-15/64
-20 1-5/8 12 1-5/8 1-35/64
-24 1-7/8 12 1-7/8 1-51/64
-32 2-1/2 12 2-1/2 2-27/64
Dash Size Nominal Size Threads per In. Male Thread O.D. Female Thread I.D.
-4 9/16 18 9/16 1/2
-6 11/16 16 11/16 5/8
-8 13/16 16 13/16 3/4
-10 1 14 1 15/16
-12 1-3/16 12 1-3/16 1-3/32
-16 1-7/16 12 1-7/16 1-11/32
-20 1-11/16 12 1-11/16 1-19/32
-24 2 12 2 1-29/32
Dash Size Nominal Size Threads per In. Male Thread O.D. Female Thread I.D.
-4 7/16 20 7/16 25/64
-5 1/2 20 1/2 29/64
-6 5/8 18 5/8 9/16
-8 3/4 16 3/4 11/16
-10 7/8 14 7/8 13/16
-12 1-1/16 14 1-1/16 63/64
Nom. Tube O.D. (in.) Dash Size Nominal Size Threads per In. Male Thread O.D. Female Thread I.D.
1/8 -2 5/16 24 5/16 17/64
3/16 -3 3/8 24 3/8 21/64
1/4 -4 7/16 20 7/16 25/64
5/16 -5 1/2 20 1/2 29/64
3/8 -6 9/16 18 9/16 1/2
1/2 -8 3/4 16 3/4 11/16
5/8 -10 7/8 14 7/8 13/16
3/4 -12 1-1/16 12 1-1/16 31/32
1 -16 1-5/16 12 1-5/16 1-15/64
1 1/4 -20 1-5/8 12 1-5/8 1-35/64
1 1/2 -24 1-7/8 12 1-7/8 1-51/64
2 -32 2-1/2 12 2-1/2 2-27/64
Dash Size Flange O.D. Flange Thickness
-8 1-3/16 .265
-10 ** 1.338 [34mm] .276
-12 1-1/2 .270
-16 1-3/4 .320
-20 2 .322
-24 2-3/8 .325
-32 2-13/16 .390
Dash Size Flange O.D. Flange Thickness
-8 1-1/4 .312
-12 1-5/8 .348
-16 1-7/8 .380
-20 2-1/8 .420
-24 2-1/2 .500
-32 3-1/8 .500