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UNC and UNF fasteners in Britain

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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?
Parents
  • Now an even more challenging question for anyone: How do you determine whether an internal thread is 3/16 BSF (internal diameter 0.1475 inches, 32 TPI) or 2BA  (internal diameter 0.1467 inches, 31.4 TPI)? Now because that's far too easy ? I'll add that the first couple of threads are damaged so I can't just try a screw of each size in it - I'm going to need to buy a tap to "reform" the thread. And if it's the wrong one it will just completely destroy the rest of the thread.


    To be honest, since it's in a UK built milling machine from 1940s-1950s I'm 99.9% confident it will be BSF, but it will be very embarrassing if I get it wrong - I'm assuming that the steel's going to be pretty resistant to drilling out and retapping!


    Having finally got around to fitting a new chuck to my lathe which involved tapping a 3/4" BSF thread in the backplate I feel like I'm on a roll now - this milling machine's been just sitting there for about 15 years waiting for me to get around to replacing this tiny (but very vital) screw ?


    Cheers,


    Andy
Reply
  • Now an even more challenging question for anyone: How do you determine whether an internal thread is 3/16 BSF (internal diameter 0.1475 inches, 32 TPI) or 2BA  (internal diameter 0.1467 inches, 31.4 TPI)? Now because that's far too easy ? I'll add that the first couple of threads are damaged so I can't just try a screw of each size in it - I'm going to need to buy a tap to "reform" the thread. And if it's the wrong one it will just completely destroy the rest of the thread.


    To be honest, since it's in a UK built milling machine from 1940s-1950s I'm 99.9% confident it will be BSF, but it will be very embarrassing if I get it wrong - I'm assuming that the steel's going to be pretty resistant to drilling out and retapping!


    Having finally got around to fitting a new chuck to my lathe which involved tapping a 3/4" BSF thread in the backplate I feel like I'm on a roll now - this milling machine's been just sitting there for about 15 years waiting for me to get around to replacing this tiny (but very vital) screw ?


    Cheers,


    Andy
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