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UNC and UNF fasteners in Britain

Arran Cameron
Somebody will know the answer to this…


Almost all British machinery manufactured before 1950 used Whitworth, BSF, or BA fasteners. Manufacturers moved towards using metric fasteners in the 1970s and these have been the most commonly available and used family since 1980, although the proposal to use metric fasteners dates back 1965. Whitworth and BSF officially became obsolete in 1948 following an agreement between the UK, US, and Canada to standardise on the American UNC and UNF fasteners for future use. UNC and UNF fasteners were used in British machinery manufactured in the 1950s, 60s, and 70s where they gradually replaced Whitworth and BSF before themselves being replaced by metric fasteners.


1. Were UNC and UNF fasteners used across most industries in the UK or were they largely confined to specific industries such as automotive and machine tools? Were they regularly used in railways or shipbuilding?

2. Were the numbered sizes smaller than ¼ inch commonly used or did industry stick with BA fasteners until they moved to using metric fasteners?

3. Were UNC and UNF fasteners commonly used in construction? What are the most common family of fasteners used to hold together 1960s tower blocks and university buildings?

4. Was it easy to buy UNC and UNF fasteners from hardware and DIY shops in the 1960s and 70s or did they move directly from selling Whitworth and BA fasteners to metric fasteners?
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    Andy,

    One thing that has occurred to me is that if it is only the first two or three threads that are damaged it may be practical to run a plug tap a couple of turns into the hole and it may not matter whether you use 3/16 BSF or 2BA as the difference between the two is not major. Of course this is assuming that the damaged threads are a small proportion of the total length of thread. My guess would be you are dealing with BSF as you suspect, but being a slightly smaller diameter (both at thread top and bottom) the BA tap might be safe as a first try even if it turns out to be BSF. Sadly though I used to have my father's old BA tap and die set, it vanished during a move (I think in the direction of my brother....).
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  • 0
    Andy,

    One thing that has occurred to me is that if it is only the first two or three threads that are damaged it may be practical to run a plug tap a couple of turns into the hole and it may not matter whether you use 3/16 BSF or 2BA as the difference between the two is not major. Of course this is assuming that the damaged threads are a small proportion of the total length of thread. My guess would be you are dealing with BSF as you suspect, but being a slightly smaller diameter (both at thread top and bottom) the BA tap might be safe as a first try even if it turns out to be BSF. Sadly though I used to have my father's old BA tap and die set, it vanished during a move (I think in the direction of my brother....).
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