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[lancelot]

Hello all,
working at the moment on making some studs for an engine I am building, the drawing calls for 1ba screwed rod with the nuts being 5/16'' A/F, [american fine, anf, or ?] this does not seem right , or am I missing something. I can not see any listings for A/F tooling anywhere, any info on this one would be appreciated.
All the best for now,
John.

[ron]

John
I think it means the nut is 5/16" across the flats with the thread being 1BA?
Ron

[lancelot]

Good one Ron, I did not tkink of that, I will now have to check my b/a tap and die set. Thanks again.
All the best for now,
John.

[houstonceng]

I came across a lot of "Old-uns" who incorrectly called "AF" "American Fine". Best explanation I could come up with was that pre-WW2, near all UK tooling and fixings were Whitworth or BSF with some BA. None of these threads had "Across Flats" sizes marked on spanners.

Then the stuff from the US of A arrived and additioinal spanners had to be bought (My late father's original set of A/F Sockets were "made in the US of A"). Now like the false story about POSH meaning Port Out Starboard Home (which it most definitely don't) I suspect someone stated the rumour that, say, the '9/16" A/F' on the spanner mean "American Fine" and - like all of these rumours - it was only a split second before everyone was calling it that.

Then came metric - - - -

When I asked for a M14 nut at my Rover agent - IIRC for fixing the steering wheel - on the first Rover to use metric fixings he said "Is that the size of the spanner ?"

[abby]

I always thought it was american fred !
What is the origin of posh ?
Ab.

[houstonceng]

abby said:

I always thought it was american fred !
What is the origin of posh ?
Ab.

See "POSH" and other langiage myths" by Michael Quinion - published bt Penguin Books £12.99.

OR

Visit the website of "The Word Detective" at www.word-detective.com/

Warning. The latter site can become very time consuming as you look ip all those strange terms like Drum = Flat/House and Kettle = Watch, You have been warned.

[houstonceng]

Getting back to Model Engineering rtaher than myths about the origin of words - - - - - -

Last night at "The Club", one of the "old-uns" had a set of Whitworth threat gauges which started a little debate.

For example, one was marked "4 0.320", another "8 0.160". Obviously, the first number was the TPI. But what is the second number ?

Theories abounded and settled on "the depth of the tread". Unfortunately, a number of sources (including the late, great George Thomas) state that the depth of a 55 degree Whitworth thread is 0.640" x Pitch where Pitch = 1/TPI.

Anyone have any clues why the second figures on the gauges seem to be exactly twice as big as the thread depth we all calculated?