BSW AND BSF THREAD GAUGES
Gauges for testing parallel threads having a full form Whitworth
profile are manufactured to
BS 84:1956, and BS 919: Part 2: 1971.
BS 84 specifies basic information for the Whitworth form,
and tabulates diameters for threads designated BSW and BSF.
BSW is a coarse thread series from 1/8”
to 6” diameter.
BSF is a fine thread series from 3/16”
to 3” diameter.
Basic form Whitworth Thread
| H= 0.960491 | H/6= 0.60082p |
| H=2/3H=0.640327p | r=0.137329p |
Provision is made for three classes of fit for external threads. Close, Medium
and Free, and two classes for internal threads. Medium and Normal.
Close class applies to threads requiring a snug fit, and is only used where
there is a controlled accuracy of form and pitch. Medium class applies to
better class interchangeable threads. Free and Normal classes apply to the
majority of commercial quality threads.
Unless otherwise specified by the customer, gauges for all internal and external
product threads are made to the basic sizes as specified in BS 84, with the
exception of Medium and Free fit bolts up to and including 3/4” diameter.
These have a plating allowance, the magnitude of which is dependent on diameter
and pitch.
BS 919: Pt 2: 1971 specifies the limits
for gauges with threads having a full form profile.
The gauge limits are dependent upon the diameter/pitch. Generally the larger
the diameter the larger the limit, within defined bands.
The types of gauge which are recommended to be used are similar to those used
for ISO and Unified threads, with the exception that the Go plugs and Go rings
test the major, effective and minor diameters of the product threads (Maximum
material limit). The Not Go gauges test the effective diameter only.
|
| Size | G0 | NOGO | 'E' | Go | NOGO | ROLLER | KNIFE |
| Class of fit | Class of fit | Class of fit | |||||
| MED | MED | STD | MED | ANY | ANY | ||
| 1/8? x 40 BSW | 0280 | 0281 | 0280A | 1000 | 1001 | 1920 | 2120 |
| 3/16? x 24 BSW | 0282 | 0283 | 0282A | 1002 | 1003 | 1921 | 2121 |
| 1/4? x 20 BSW | 0284 | 0285 | 0284A | 1005 | 1006 | 1922 | 2122 |
| 5/16? x 18 BSW | 0286 | 0287 | 0286A | 1007 | 1008 | 1923 | 2123 |
| 3/8? x 16 BSW | 0288 | 0289 | 0288A | 1009 | 1010 | 1924 | 2124 |
| 7/16? x 14 BSW | 0290 | 0291 | 0290A | 1011 | 1012 | 1925 | 2125 |
| 1/2? x 12 BSW | 0292 | 0293 | 0292A | 1013 | 1014 | 1926 | 2126 |
| 9/16? x 12 BSW | 0294 | 0295 | 0294A | 1015 | 1016 | 1927 | 2127 |
| 5/8? x 11 BSW | 0296 | 0297 | 0296A | 1018 | 1019 | 1928 | 2128 |
| 3/4? x 10 BSW | 0298 | 0297 | 0298A | 1020 | 1021 | 1929 | 2129 |
| 7/8? x 9 BSW | 0300 | 0301 | 0300A | 1022 | 1023 | 1930 | 2130 |
| 1? x 8 BSW | 0302 | 0303 | 0302A | 1024 | 1025 | 1931 | 2131 |
| 11/8? x 7 BSW | 0304 | 0305 | 0304A | 1026 | 1027 | 1932 | 2132 |
| 11/4? x 7 BSW | 0306 | 0307 | 0306A | 1028 | 1029 | 1933 | 2133 |
| 13/8? x 6 BSW | 0308 | 0309 | 0308A | 1030 | 1031 | 1934 | 2134 |
| 11/2? x 6 BSW | 0310 | 0311 | 0310A | 1032 | 1033 | 1935 | 2135 |
| 3/16? x 32 BSF | 0250 | 0251 | 0250A | 1060 | 1061 | 1900 | 2100 |
| 1/4? x 26 BSF | 0252 | 0253 | 0252A | 1062 | 1063 | 1901 | 2101 |
| 5/16? x 22 BSF | 0254 | 0255 | 0254A | 1064 | 1065 | 1902 | 2102 |
| 3/8? x 20 BSF | 0256 | 0257 | 0256A | 1066 | 1067 | 1903 | 2103 |
| 7/16? x 18 BSF | 0258 | 0259 | 0258A | 1069 | 1070 | 1904 | 2104 |
| 1/2? x 16 BSF | 0260 | 0261 | 0260A | 1071 | 1072 | 1905 | 2105 |
| 9/16? x 16 BSF | 0262 | 0263 | 0262A | 1073 | 1074 | 1906 | 2106 |
| 5/8? x 14 BSF | 0264 | 0265 | 0264A | 1075 | 1076 | 1907 | 2107 |
| 3/4? x 12 BSF | 0266 | 0267 | 0266A | 1077 | 1078 | 1908 | 2108 |
| 7/8? x 11 BSF | 0268 | 0269 | 0268A | 1079 | 1080 | 1909 | 2109 |
| 1? x 10 BSF | 0270 | 0271 | 0270A | 1081 | 1082 | 1910 | 2110 |
| 11/8? x 9 BSF | 0272 | 0273 | 0272A | 1083 | 1084 | 1911 | 2111 |
| 11/4? x 9 BSF | 0274 | 0275 | 0274A | 1085 | 1086 | 1912 | 2112 |
| 13/8? x 8 BSF | 0276 | 0277 | 0276A | 1087 | 1089 | 1913 | 2113 |
| 11/2? x 8 BSF | 0278 | 0279 | 0278A | 1089 | 1090 | 1914 | 2114 |
