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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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    Denis McMahon:

    In the 1960s bicycles were a bit of a mixture of thread types. BA seemed to be used for some of the smaller bolts, e.g. fixing mudguard stays to frame.




    Manufacturers and installers of aftermarket accessories probably used whatever fasteners they could obtain most easily at the lowest price.






    I believe that the British Cycle threads are still used on "cycle specific" parts, such as threads associated with bearings, for which the fine thread form is highly suitable. 




    There are still a few BSC thread sizes in regular use today although nuts fit metric spanners. A 5/16" Whitworth spanner is the size that fits pedals as well as axle nuts on small children's bikes, and is by co-incidence almost the same size as a 15mm spanner. A 17mm spanner fits the nuts used on 3/8" diameter axles (often erroneously referred to as 10mm) but this is a standard metric spanner with no Whitworth equivalent.


    Female BMX hubs are attached to the frame with a strange hybrid bolt that is 3/8" UNF (24 TPI as opposed to 26 TPI for BSC of the same diameter) with a 17mm head. 



     

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  • 0

    Denis McMahon:

    In the 1960s bicycles were a bit of a mixture of thread types. BA seemed to be used for some of the smaller bolts, e.g. fixing mudguard stays to frame.




    Manufacturers and installers of aftermarket accessories probably used whatever fasteners they could obtain most easily at the lowest price.






    I believe that the British Cycle threads are still used on "cycle specific" parts, such as threads associated with bearings, for which the fine thread form is highly suitable. 




    There are still a few BSC thread sizes in regular use today although nuts fit metric spanners. A 5/16" Whitworth spanner is the size that fits pedals as well as axle nuts on small children's bikes, and is by co-incidence almost the same size as a 15mm spanner. A 17mm spanner fits the nuts used on 3/8" diameter axles (often erroneously referred to as 10mm) but this is a standard metric spanner with no Whitworth equivalent.


    Female BMX hubs are attached to the frame with a strange hybrid bolt that is 3/8" UNF (24 TPI as opposed to 26 TPI for BSC of the same diameter) with a 17mm head. 



     

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