USEFUL DATA

 

Here is a list of all common screwthreads listed in size order in .pdf format for you to download  – I will work on updating the IMPERIAL measurements.

I find the UNF and UNC are the most useful, followed by the  B.A. threads – the metric seldom fit any old British guns.

Percussion Nipples are often 1/4 BSF,  which DOESN’T correspond to 1/4 UNF.

click here to download  3 landscape pages of the table as a pdf;-  Useful thread Data

Or use the table here;-

cablesfarm.co.uk
USEFUL GUN THREADS FOR RESTORATION WORK Copyright Tim Owen 2016
    IMPERIAL METRIC DIMENSIONS
Type SIZE dia T.P.I TAP dia Pitch CLR Tap Angle
B.A. 10 0.689 72.6 0.051 1.700 0.350 2 1.30 47.5
B.A. 9 0.748 65.1 0.063 1.900 0.390 2.2 1.60 47.5
ISO M2 0.079 0.063 2.000 0.400 2.3 1.60 60
B.A. 8 0.087 59.17 0.067 2.200 0.430 2.5 1.70 47.5
DIM 3/32nd >>>>>>>>>>>>>>>>>>>>>>>>>>>> 0.094 2.383
B.A. 7 0.098 52.91 0.079 2.499 0.480 2.8 2.00 47.5
ISO F M2.5 0.098 72.56 0.083 2.500 0.350 2.9 2.10 60
ISO C M2.5 0.098 56.44 2.500 0.450 2.9 2.10 60
UNF No. 3 0.099 56 0.079 2.515 0.454 2.8 2.00 60
UNC No. 3 0.099 48 0.079 2.515 0.529 2.8 2.00 60
B.A. 6 0.110 47.85 0.091 2.799 0.530 3.2 2.30 47.5
UNF No. 4 0.112 48 0.094 2.845 0.529 3.2 2.40 60
UNC No. 4 0.112 40 0.094 2.845 0.635 3.2 2.40 60
ISO F M3 0.118 72.56 0.102 3.000 0.350 3.4 2.60 60
ISO C M3 0.118 50.8 0.098 3.000 0.500 3.4 2.50 60
DIM 1/8th >>>>>>>>>>>>>>>>>>>>>>>>>>> 0.125 0.000 3.175
UNF No. 5 0.125 44 0.106 3.175 0.577 2.70 60
UNC No. 5 0.125 40 0.102 3.175 0.635 2.60 60
BSW 1/8th 0.125 40 0.098 3.175 0.635 2.50 55
B.A. 5 0.126 43.1 0.102 3.200 0.589 2.60 47.5
ISO F M3.5 0.138 72.57 0.126 3.500 0.350 3.20 60
ISO C M3.5 0.138 42.33 0.114 3.500 0.600 2.90 60
UNF No. 6 0.138 40 0.114 3.505 0.635 2.90 60
UNC No. 6 0.138 32 0.112 3.505 0.794 2.85 60
B.A. 4 0.142 38.46 #VALUE! 3.599 0.660 3.10 47.5
DIM 5/32 nd>>>>>>>>>>>>>>>>>>>>>>>> 0.156 3.967
ISO F M4 0.158 50.8 0.138 4.000 0.500 4.5 3.50 60
ISO C M4 0.158 36.29 0.130 4.000 0.700 4.5 3.30 60
B.A. 3 0.161 34.84 0.134 4.100 0.730 4.5 3.40 47.5
UNF No. 8 0.164 36 0.125 4.166 0.706 4.5 3.50 60
UNC No. 8 0.164 32 0.125 4.166 0.794 4.5 3.50 60
ISO F M4.5 0.177 50.8 0.154 4.500 0.500 5 3.90 60
ISO C M4.5 0.177 33.87 0.142 4.500 0.800 5 3.60 60
B.A. 2 0.189 31.35 0.035 4.788 0.810 5.2 0.90 47.5
DIM 3/16th >>>>>>>>> 0.188 4.763
BSW 3/16th 0.188 24 0.146 4.763 1.058 5.1 3.70 55
BSF 3/16th 0.188 32 0.154 4.763 0.794 5.1 3.90 55
UNF No. 10 0.190 32 0.161 4.826 0.794 4.10 60
UNC No. 10 0.190 24 0.154 4.826 1.058 3.90 60
ISO F M5 0.197 50.8 0.177 5.001 0.500 5.5 4.50 60
ISO C M5 0.197 31.75 0.167 5.001 0.800 5.5 4.25 60
B.A. 1 0.209 28.22 0.177 5.309 0.900 4.50 47.5
UNF 12 0.216 24 0.185 5.486 1.058   4.70 55
UNC 12 0.216 28 0.181 5.486 0.907   4.60 55
DIM 7/32nd>>>>>>>>> 0.219 5.558
B.A. 0 0.236 25.4 0.201 5.999 1.000 5.10 47.5
ISO F M6 0.236 33.86 0.205 6.000 0.800 6.6 5.20 60
ISO C M6 0.236 25.4 0.197 6.000 1.000 6.6 5.00 60
DIM 1/4th >>>>>>>>>>> 0.250 6.350
UNF 1/’4th 0.250 28 0.195 6.350 0.907 5.60 60
UNC 1/4th 0.250 20 0.19 6.350 1.270 0.00 60
BSW 1/4th 0.250 20 0.186 6.350 1.270 5.00 55
BSF 1/4th 0.250 26 0.209 6.350 0.977 5.30 55
BSPF ? 1/4th 0.250 26 0.000 6.350 0.977
BSF 9/32nd 0.281 26 0.240 7.142 0.977 6.10
AS str. Pipe 1/16th 0.281 27 0.000 7.137 0.941
BSPP 1/16th 0.304 28 0.000 7.724 0.907
DIM 5/16th >>>>>>>>>>> 0.313 7.938
BSF 5/16th 0.313 22 0.268 7.938 1.155 6.80 55
BSW 5/16th 0.313 18 0.256 7.938 1.411 6.50 55
BSB 5/16th 0.313 26 0.276 7.938 0.977 7.00
UNF 5/16th 0.313 24 7.938 1.058 6.80
UNC 5/16th 0.313 18 7.938 1.411 6.60
ISO F M8 0.315 25.4 0.285 8.000 1.000 9 7.25 60
ISO C M8 0.315 0.276 8.000 1.250 9 7.00 60
AS str. Pipe 1/8th 0.378 27 9.606
BSPP 1/8th 0.383 28 0.339 9.728 8.60

 

Brass threads are all 26 t.p.i. as are British Standard Cycle threads. Model Engineer threads are available in 40 or 32 t.p.i from 1/8 to ½ dia.
Early threads were made from hand made die plates and taps that were derived from earlier generations of handmade dies and taps so that the diameters tended to vary considerably and the pitch was not standard.
A degree of standardisation was beginning to be implemented from late 18th early 19th century and percussion guns are likely to have threads similar to modern BSF or UNF ( but 1/4 BSF  26 t.p.i  is NOT the same  as  1/4 UNF 28 t.p.i – the other sizes are the same?)  and Whitworth or UNC threads – you’ll find those threads are quite common on British guns, but often the diameter is a bit out..
The thread profiles was almost always different from modern threads – thread angles were shallower and the tops and bottoms of the threads were almost always much more rounded than modern threads, but provided the part you have made is not hardened it will usually form itself to fit.
 Posted by at 6:46 pm