Threads (pun) in general

Discussion in 'Engineers' Talk' started by flymoe, Dec 19, 2005.

  1. flymoe

    flymoe New Member

    Why is it that nobody talks about imperial threads anymore?
    These threads were the standard that everyone went by.
    It does have a ring about it to name British Armstrong,
    Whitworth,British Standard Fine and not to mention CEI or BSC. It was quite clear that Whitworth was used as blind threads in alloy and BSF in steel. The CEI/BSC thread was unique in having 26 tpi. irrespective of diameter. Then some smart alec decided that threads should be "unified"..UNF and UNC! I mean what spanner in "unified" could fit the same nut as 1/4" and 3/16" BSF and Whit. In my nut assortment in the shed, I still have cadmium plated, (illegal plate)cycle thread nuts and bolts! Come on Chaps, lets hear it from the old school!!
     
  2. Hitch.

    Hitch. New Member

    Theyre ok till they get mixed up with the metrics, M16 bolts into 5/8" UNC, goes a few threads then thats it :(


    You gotta admit though flymoe, the metric system is much nicer :)
     
  3. jasonb

    jasonb New Member

    One of my hobbies is model engineering in which imperial measurement is still the norm.

    Plenty of 26, 32 & 40 tpi threads. Letter, number and fractional drill sizes and most things measured to 0.001"

    Most models are of old subjects so they scale easily in imperial and all the locomatives run on track that has imperial gauges.

    Jason
     
  4. DB

    DB New Member

    Of course we still use BSP for pipe threads
     
  5. Dewy

    Dewy New Member

    I still prefer BSW (Whitworth) for strngth.
    Sam Whitworth may have made a mistake when making the very first machine thread at 55° instead of the later 60° used by all other threads but his mistake is a much stronger thread.
    I bought a concrete sectional garage about 10 years ago which still used whitworth bolts as had been used on their first garage in 1959. Unfortunately the roof trusses needed a 1/4" whitworth box spanner which I couldn't find anywhere.
    At least we can still ask for imperial threads by name in inches unlike when I was in South Africa when they went metric in the early 70s. At first you could get either metric or imperial then at a stroke they made it illegal to sell anything in inches. We had to ask for 12.7mm whitworth nuts instead of 1/2".
    My father was building an extension when the law changed and had to submit his plans showing 229mm bricks instead of 9".
    The day I left my job some barsteward nicked my 1" mic and old Imperial Zeus book because they could no longer buy them there.
     
  6. Hitch.

    Hitch. New Member

    And the compatability between UNC/UNF/BSF/BSW, both use the same pitch except for 3/8" is it? Nuts and bolts will go together, but thread angles are different, 55 and 60.
     
  7. handyman.

    handyman. New Member

    yes hm, he metric systems the way to go.

    If you really like imperial threads, go get a job in the aircraft industry, as its all still imperial (as its run by the USA) or just go and stay in america
     
  8. dirtydeeds

    dirtydeeds New Member

    OK lets complicate things a bit more

    american metric threads are not the same as metric threads for the rest of the world. the pitchs are the same but the shape of the threads are different

    my mate has a modern harley with mainly metric nuts and bolts (but as with all things american stuff some fittings are still AF with AF threads)

    he is fully aware of the differences (having worked as a mechanic in california for about 18months) long and short of it is that the two metric threads are not compatible
     
  9. dirtydeeds

    dirtydeeds New Member

    perhaps an engineer can explain better than me
     
  10. handyman.

    handyman. New Member

    I didnt even know usa had anything metric like that!

    What i couldnt believe when i started at the jet engine refurb was that they were all imperial.....all screws, nuts, diameters, all sizes when assembling etc
     
  11. flymoe

    flymoe New Member

    Mr. Handyman...
    It's not necessary to go to the USA to find AF sizes of threadery. Just try taking apart a Briggs and Stratton Mower with metric spanners !!!!

    Flymoe
     
  12. Hitch.

    Hitch. New Member

    I know that the USA have been slowly moving over to a metric system and is now widely used.
    We use ISO metric, the USA use Metric.
    The angles are the same, as are the pitches, the difference i believe is the tolerances and thread profiles, some having a shallower radius on the roots of the threads.
     
  13. ChrisMo

    ChrisMo New Member

    Briggs & Stratton engines are American.
     
  14. flymoe

    flymoe New Member

    Hello ChrisMo..
    Did you also know that in the B+S factorys, the motors are machined, assembled, tested, packed into crates and shipped, all by robots.
     
  15. mudhut

    mudhut New Member

    stripped down a b&s engine the other day, fell over when i saw the PLASTIC camshaft :eek:
     
  16. Harry Stottle

    Harry Stottle Screwfix Select

    Talking of Briggs & Stratton, has anyone noticed the deterioration in quality of garden machinery? I'm on my third mower in 12 years, each has been inferior to the last. The latest, a Hayter seems to have been designed and built on the cheap although it was dear enough, I've had cables fail, a bolt fall out, top hat washers come off and Briggs & Stratton's legendary bad starting,(apparently they're known in the trade as "Briggs & Scrap'em") Last summer, for every hour spent mowing I must have spent half an hour repairing.
    Does anyone know of a make of mower that starts every time, mows and stops when you want it to?
     
  17. Hitch.

    Hitch. New Member

    ....Did you also know that in the B+S factorys, the motors are machined, assembled, tested, packed into crates and shipped, all by robots.


    The JCB factory, i reckon that would be worth a visit. Anyone been?
     
  18. flymoe

    flymoe New Member

    Hello Quentin...
    If you have had so much trouble with your mowers, a bit of preventative maintenance would be in order.
    The way to go would be to re-tap the threads to bsc which is 26 tpi.and use some blue loctite. The replacement bolts can be obtained from RS or Custom fasteners. These threads were designed to resist vibration due to the fine thread,and with loctite you should be home and dry!!
     
  19. Hitch.

    Hitch. New Member

    Either that, or just put a spring washer on each bolt....?
     
  20. rcplumber

    rcplumber New Member

    I worked for Shelbourne Reynolds for a few years, we made farm machinery mainly for export to the states and although we worked in metric every thing was to an imperial measurement for the american market,bit like a metric inch or evan a metnch:)
     

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