bolt / nut threads

[RoyC]

hello roy I think you mean a 5/16 UNC/NC/ ANC tap fits? NF/UNF/ANF is 24 threads to inch. ps I have not been to the pub , man/ person flu has struck!

Sorry, you are quite right.
It has 5/16 NC 18 on the tap.

[berger]

my tap has a squealing washer , and it drips. I must change it. the girlfriend likes the noises it makes. it drives me round the bend 

[RoyC]

my tap has a squealing washer , and it drips. I must change it. the girlfriend likes the noises it makes. it drives me round the bend 

She must like drips then.   

[Gerry]

NC is National Course (the original American thread system) UNC is Unified National course. UNC was developed primarily for general use world wide to try and bring all countries to use the same thread system. Primarily for aircraft. NF National fine is the same as Unified National fine other than the tops of the threads (as per UNC) are flattened not pointed. Both these threads use a 60 degree angle. Whitworth was in use long before BSF British Standard Fine. BSF has a smaller hex head than whitworth and was done to save steel. The British system threads are 55 degrees. So when you see a spanner with 5/16 3/8 on one end or 5/16W it means that it will suit a 5/16 whitworth bolt or nut and a 3/8 BSF, It is not the same as the American system where the spanner is marked with the across flats size of the head not the bolt size. Don't ask me why the British spanners have such odd across flats sizes, the mind boggles... BA or British Association is another odd ball set of sizes and used to be used on most British electrical items such as your dynamos and magnetos. 1BA being the largest size down to around 10BA which is about as thin as a knats you know what. I have a Britool set of these sockets with 9/32" square drive!!! every one else uses 1/4" lol
The Metric system is probably the best system (invented in Britain so I have been told and much too easy to understand so was rejected by them) USA would have adopted the Metric system but for the fact that the vast amount of machinery in use would have causedmassive headaches so was rejected. All this to the best of my knowledge. Correct me if I'm wrong. Cheers. Gerry

[Bsareg]

I have (and use) 0 BA taps and dies. Some tables show upto 16 BA but, your right, I've never seen anything over 10 BA. They must be used  for repairing fractured spider legs !!

[Rex]

I don't see anything difficult to understand about the old Imperial system. Whit was a coarse thread, BSF was finer and BSCY finer still. Then there was BSP threads for pipework and other more esoteric stuff.
0BA was the largest BA thread, and it went down to watchmaker sizes (32BA rings a bell), so also simple.
All down to the difficulties experienced with differing equipment threads on Lend-Lease stuff during WW2, and as the US was the equipment supplier the standards were UNF and UNC....(well, for a few years anyway. Most industry went from Imperial straight to Metric, and although simpler the thread forms were no better in use and the general range more limited).

[Swarfcut]

Anyone come across AF or Whitworth headed bolts with ISO Metric Threads? Seems it was a halfway house with the usual metric threads on nuts and bolts, but the nuts and bolts had the American AF or Whitworth hexagon sizes. It enabled the UK (and others) auto industry to move towards a metric standard, yet still use existing spanner sizes. Found on mid fifties/sixties Fords, especially engines and gearboxes produced in Continental Europe. Confused a lot of folks, including me!

Swarfy.

[berger]

aannnd then we have BSB --- how many threads do we need? 26 to the inch I think same as BSC but 55 degree angle if I remember and BSC 60 degrees, o well so long as winter stays between 55 and 60 degrees F  ----I will be happy

[Gerry]

I have (and use) 0 BA taps and dies. Some tables show upto 16 BA but, your right, I've never seen anything over 10 BA. They must be used  for repairing fractured spider legs !!

Yep 0BA was the largest. Got a mate who overhauls magnetos and dynamos here in Adelaide and I repaired about 10 points off MO1 magdynos by drilling out the stripped threads for the stationary points and fitted metric threaded bushes drilled and tapped 5BA (broke a couple of taps in the process though, too bloody heavy handed

[mikeb]

I don't see anything difficult to understand about the old Imperial system

on the same debate my 15 year old son insisted I watch this: https://www.youtube.com/watch?v=r7x-RGfd0Yk
worth a watch

[RoyC]

I don't see anything difficult to understand about the old Imperial system

on the same debate my 15 year old son insisted I watch this: https://www.youtube.com/watch?v=r7x-RGfd0Yk
worth a watch

Yes but, it's easier for me to visualize 1ft than 304.8 mm.
I know, I'm old.

[muskrat]

G'day fellas.
I'm lucky to have grown up (but can be immature forever) with both systems. I will quite often use both in the same sentence. "If I cut 6mm off that it will save a few ounces." At a recent medical I said 5'7" and 76Kg. I vaguely remember pounds, shillings and pence, I was only 5 when we changed over to $ but remember a Paddle Pop was tupence and the new price was 5c.
Cheers 

[RoyC]

G'day fellas.
I'm lucky to have grown up (but can be immature forever) with both systems. I will quite often use both in the same sentence. "If I cut 6mm off that it will save a few ounces." At a recent medical I said 5'7" and 76Kg. I vaguely remember pounds, shillings and pence, I was only 5 when we changed over to $ but remember a Paddle Pop was tupence and the new price was 5c.
Cheers

The only living thing weight that I use is Stones and lbs, I am 11st 10lbs.

[Bsareg]

Have you noticed that in a metric world whenever a new baby is announced, the weight is still given in pounds and ounces.

[bsa-bill]

And before metrication in the UK engine capacity was measured in cc - ????? - proves what exactly