Whitworth thread sizes[4]
| Whitworth size (in) | Core diameter (in) | Threads per inch | Pitch (in) | Tapping drill size |
| 1/16 |
0.0411 |
60 |
0.0167 |
Number Drill 56 (1.2Â mm) |
| 3/32 |
0.0672 |
48 |
0.0208 |
Number Drill 49 (1.85Â mm) |
| 1/8 |
0.0930 |
40 |
0.025 |
Number Drill 39 (2.55Â mm) |
| 5/32 |
0.1162 |
32 |
0.0313 |
Number Drill 30 (3.2Â mm) |
| 3/16 |
0.1341 |
24 |
0.0417 |
Number Drill 26 (3.7Â mm) |
| 7/32 |
0.1654 |
24 |
0.0417 |
Number Drill 16 (4.5Â mm) |
| 1/4 |
0.1860 |
20 |
0.05 |
Number Drill 9 (5.1Â mm) |
| 5/16 |
0.2414 |
18 |
0.0556 |
Letter Drill F (6.5Â mm) |
| 3/8 |
0.2950 |
16 |
0.0625 |
5/16Â in (7.94Â mm) |
| 7/16 |
0.3460 |
14 |
0.0714 |
Letter Drill U (9.3Â mm) |
| 1/2 |
0.3933 |
12 |
0.0833 |
Letter Drill Z (10.5Â mm) |
| 9/16 |
0.4558 |
12 |
0.0833 |
12.1Â mm (0.4764Â in) |
| 5/8 |
0.5086 |
11 |
0.0909 |
13.5Â mm (0.5315Â in) |
| 11/16 |
0.5711 |
11 |
0.0909 |
15Â mm (0.5906Â in) |
| 3/4 |
0.6219 |
10 |
0.1 |
16.27Â mm (0.6406Â in) |
| 13/16 |
0.6845 |
10 |
0.1 |
18Â mm (0.7087Â in) |
| 7/8 |
0.7327 |
9 |
0.1111 |
19.25Â mm (0.7579Â in) |
| 15/16 |
0.7953 |
9 |
0.1111 |
20.75Â mm (0.8169Â in) |
| 1 |
0.8399 |
8 |
0.125 |
22Â mm (0.8661Â in) |
| 1 1/8 |
0.9420 |
7 |
0.1429 |
|
| 1 1/4 |
1.0670 |
7 |
0.1429 |
|
| 1 1/2 |
1.2866 |
6 |
0.1667 |
|
| 1 3/4 |
1.4939 |
5 |
0.2 |
|
| 2 |
1.7154 |
4.5 |
0.2222 |
|
| 2 1/2 |
2.180 |
4 |
0.250 |
BSF threads (use the 55 degree Whitworth thread form).
| fractional inches | decimal inches | thread per inch | BSC match | Jaw mm exact | or ~inch | drill for tap |
| 3/16 |
0.19 |
32tpi |
`= |
8.59mm |
11/32" 6pt |
5/32" |
| 7/32 |
0.22 |
28tpi |
|
? |
? |
4.6mm |
| 1/4 |
0.25 |
26tpi |
`= |
11.30mm |
-- |
5.3mm |
| 5/16 |
0.31 |
22tpi |
|
13.34mm |
17/32" |
17/64" |
| 3/8 |
0.375 |
20tpi |
|
15.24mm |
5/8" |
8.2mm |
| 7/16 |
0.44 |
18tpi |
|
18.03mm |
-- |
9.7mm |
| 1/2 |
0.50 |
16tpi |
|
20.83mm |
13/16 |
7/16" |
| 9/16 |
0.56 |
16tpi |
|
23.37mm |
15/16 |
1/2" |
| 5/8 |
0.63 |
14tpi |
|
25.65mm |
1" 6pt |
14mm |
| 11/16 |
0.69 |
14tpi |
|
27.94mm |
1'1/8" 6pt |
15.5mm |
| 3/4 |
0.75 |
12tpi |
|
30.48mm |
1"1/4 6pt |
16.75mm |
| 7/8 |
0.88 |
11tpi |
|
33.02mm |
1"5/16 |
25/32" |
| 1" |
1.00 |
10tpi |
|
37.59mm |
1"1/2 |
22.75mm |
| 1â…›" |
1.13 |
9tpi |
|
42.42mm |
1"11/16 |
26.50mm |
| 1¼" |
1.25 |
9tpi |
|
47.24mm |
1"7/8 |
28.75mm |
| 1½" |
1.50 |
8tpi |
|
56.39mm |
2"1/4 |
34.50mm |
Dash
thread
size | BSP
size
(in) | Thread pitch | Thread major
diameter | Thread minor
diameter[1][2] | A/F
(mm) | Gauge
length
(mm) |
|
Corresponding pipe | Tapping drill
size (mm) |
/in
(TPI) | (mm) | (mm) | (in) | (mm) | (in) | DN
(mm) | OD
(mm) | OD
(in) | Thickness
(mm) | BSP.PL
(Rp) | BSP.F
(G) |
| −1 |
1â„16 |
28 |
0.907 |
7.723 |
0.304 |
6.561 |
0.2583 |
|
4±0.9 |
|
|
|
|
6.60 |
6.80 |
| −2 |
1â„8 |
28 |
0.907 |
9.728 |
0.383 |
8.565 |
0.3372 |
15 |
4±0.9 |
6 |
10.2 |
0.40 |
2 |
8.60 |
8.80 |
| −4 |
1â„4 |
19 |
1.337 |
13.157 |
0.518 |
11.445 |
0.4506 |
19 |
6±1.3 |
8 |
13.5 |
0.53 |
2.3 |
11.50 |
11.80 |
| −6 |
3â„8 |
19 |
1.337 |
16.662 |
0.656 |
14.950 |
0.5886 |
22/23 |
6.4±1.3 |
10 |
17.2 |
0.68 |
2.3 |
15.00 |
15.25 |
| −8 |
1â„2 |
14 |
1.814 |
20.955 |
0.825 |
18.633 |
0.7336 |
27 |
8.2±1.8 |
15 |
21.3 |
0.84 |
2.6 |
18.75 |
19.00 |
| −10 |
5â„8 |
14 |
1.814 |
22.911 |
0.902 |
20.589 |
0.8106 |
|
|
16 |
|
|
2.6 |
- |
21.00 |
| −12 |
3â„4 |
14 |
1.814 |
26.441 |
1.041 |
24.120 |
0.9496 |
32 |
9.5±1.8 |
20 |
26.9 |
1.06 |
2.6 |
24.25 |
24.50 |
| −16 |
1 |
11 |
2.309 |
33.249 |
1.309 |
30.292 |
1.1926 |
43 |
10.4±2.3 |
25 |
33.7 |
1.33 |
3.2 |
30.40 |
30.75 |
| −20 |
1 1â„4 |
11 |
2.309 |
41.910 |
1.650 |
38.953 |
1.5336 |
53 |
12.7±2.3 |
32 |
42.4 |
1.67 |
3.2 |
39.00 |
39.50 |
| −24 |
1 1â„2 |
11 |
2.309 |
47.803 |
1.882 |
44.846 |
1.7656 |
57 |
12.7±2.3 |
40 |
48.3 |
1.90 |
3.2 |
45.00 |
45.00 |
| −32 |
2 |
11 |
2.309 |
59.614 |
2.347 |
56.657 |
2.2306 |
70 |
15.9±2.3 |
50 |
60.3 |
2.37 |
3.6 |
56.75 |
57.00 |
| −40 |
2 1â„2 |
11 |
2.309 |
75.184 |
2.960 |
72.227 |
2.8436 |
|
17.5±3.5 |
65 |
76.1 |
3.00 |
3.6 |
|
|
| −48 |
3 |
11 |
2.309 |
87.884 |
3.460 |
84.927 |
3.3436 |
|
20.6±3.5 |
80 |
88.9 |
3.50 |
4 |
|
|
| −64 |
4 |
11 |
2.309 |
113.030 |
4.450 |
110.073 |
4.3336 |
|
25.5±3.5 |
100 |
114.3 |
4.50 |
4.5 |
|
|
| −80 |
5 |
11 |
2.309 |
138.430 |
5.450 |
135.472 |
5.3335 |
|
28.6±3.5 |
125 |
139.7 |
5.50 |
5 |
|
|
| −96 |
6 |
11 |
2.309 |
163.830 |
6.450 |
160.872 |
6.3335 |
|
28.6±3.5 |
150 |
165.1 |
6.50 |
5 |
|
|
