Tripod/Camera Screw Thread

[Dave Plowman (News)]

Don't think that's so at all. There are very few sizes where AC will fit Whitworth - and none I know of where AF will fit BSF. They were essentially new threads to a common standard.

[Andy Wade]

AC and AF? Do you mean American Coarse and Fine? I've not heard of those designations before. Pre-WW2 American threads were NC and NF (National Coarse/Fine) [1]. The unification which gave us UNC and UNF [2] was, AIUI, not so much about making US parts interchangeable with our BSW and BSF as about having a common standard adopted on both sides of the pond. The Yanks would use UNC/UNF instead of NC/NF and we would use UNC/UNF instead of BSW/BSF. This was only partially successful because Whit-form parts remained widely available and used in the UK - although the automotive industry did eventually switch to Unified.

[1]

[Tim S]

Andy Wade coughed up some electrons that declared:

AF was quite common nomenclature about 20+ years ago, at least in the car fixing circles...

[Andy Wade]

... but meant "across flats" rather than "American Fine"?

[dennis]

IIRC 1/2" AF was 5/16" bolt usually UNC thread in my day but there was a lot of whitworth and UNF about.

[Dave Plowman (News)]

They tend to be known as American coarse and fine here - or at least in my circles. ;-)

Correct. But those unified threads owed far more to NF and NC than BSW or BSF.

And NC and NF are still common in the US. Sadly unified not so in the UK as it was a far better system for general use than metric, IMHO.

[The Natural Philosopher]

It went metric actually. Then it died.

[The Natural Philosopher]

Rubbish. Life wouldn't be the same without M3, 6BA, 1/8" whitworth, 1/8" UNC and UNF..

[Tim S]

Andy Wade coughed up some electrons that declared:

So it did...

[Andy Wade]

Unified first, then metric. Not straight from BSW/BSF to metric.

[Andy Wade]

And NPT.

Why, OOI?

[Dave Plowman (News)]

Yup. Most UK made cars were Unified (in the main) from after WW2 to about '70. Although electrical parts stayed with BA.

But pre-war designed parts often stayed with the older threads - one example being the MG XP series of engines that continued in production until the mid '50s. And they had some strange threads - the big end bolts were an extremely fine one - not BSF. Rileys too - until both makers adopted the BMC drive train. Although general purpose nuts and bolts might well have been Unified.

[Dave Plowman (News)]

For general purpose fixings on cars UNF was the usual - and seemed to hold rather better than standard metric. Less prone to vibrate loose.

[dennis]

They both vibrated loose unless you locked them.

Anyway having one that vibrates loose twice as slowly as another is still useless. Even ten times longer is still useless.

[Andy Dingley]

BB period, Hurricane firepower ? Spitifire firepower?

Both of them had just the same eight .303 wing guns. The Hurricane IIb did have twelve, but didn't show up until after the BoB. Both were later re-armed with the 20mm Hispano cannon, but the Spitfire got these first.

So, just another Dennisism...

[Andy Dingley]

Actually it was _after_ the war. The Unified standards weren't agreed until 1949, as a response to problems during the war. They weren't fixed at the time because the disruption to production would have been immense.

During the war itself the US kit used American National standards, previously known as United States Standard. Nothing inter-worked with British kit. For some kit, such as the Sherman Firefly, this literally meant one set of spanners to work on the (British) gun and another set of wrenches to work on the US-built chassis and engine.

[The Natural Philosopher]

I think he menas that there were abut 3 times as many hurricanes available.

[The Natural Philosopher]

A situation that more or less persisted right up to british leyland days.. I can remember AF spanners on the Chassis and whitworth or BSF on the endgine, or something.

And computers..half the screws are yank the other half metric..

[Rod]

You might be right - but Dennis claimed there were 10 times as many and phrased it in a way that seemed to say that the numerical superiority was on top of individual aircraft firepower power superiority.

[dennis]

The hurricane still got 80% of the kills.