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[GlenAnderson]

3/16” WW spanner size is 1/4”BS; approximately 11mm or 7/16” across the flats. It’s been used for 1/4”WW/BSF thread size fixings since WW2.

If you want nuts and bolts to fit your 3/16” WW spanner (that may also be stamped 1/4”BS), then you need to order 1/4”WW (or BSF) nuts and bolts.

Similarly, a 1/4”WW spanner is for 5/16” diameter threads.

Your 3/16” nuts will be 3/16” thread size, and for 1/8”WW marked spanners, which are around 8mm across the flats.

It’s confusing. If you were working on pre-WW2 stuff, then you’d find that the heads of (the surviving original) nuts and bolts were much bigger relative to their thread sizes and actually correspond 1/4”thread to 1/4” WW marking.

[Worf]

Got it 

[Calum]

Indeed, as I said earlier the sizes changed but the spanners never did.

You can still buy prewar sizes fasteners but they are expensive and hard to get, we usually make our own if we need them (we do have a stock in the stores for 1/2" to 1" Whit 'full nuts'). We don't use them often, on some jobs and on the engines in some visible areas but they are expensive to produce so they get used sparingly.

Having said all this whatever you are working on is most probably post war sizes. If it is 1/4" Whit nuts you actually need (3/16" Spanner size) I have thousands. PM me your address

[Herald1360]

PS... BA is short for British Armstrong ... I think.

British Association- an interesting metric(!) thread.

[w3526602]

A while ago I got some 5/16" UNF brass manifold nuts so I would not have to deal with rusted and seized steel nuts ever again. 

Hi David,

My personal preference, when buying nuts for an exhaust system, are LONG nuts ... so that my spanner gets a decent grip, when the nut is buried deep between hot "bananas", and especially when I'm approaching from underneath the "manifold to front pipe flanges".

I frequently have to use a 1/4" drive socket, plus a prial of extension bars.

Ebay recognises "LONG NUTS", but I can't remember if I have ever asked for "LONG BRASS NUTS".

Smokey 2A mentioned bicycle nuts and bolts. I have always (well since about 1950) referred to these as CYCLE THREAD, and everybody seemed to know what I was talking about (Herd ignorance?)  Metric? Yeah, I can accept that, but could they all be circa 1mm pitch ... regardless of diameter? I seem to remember very fine pitch on the bearing retaining cups on steering head-stocks and pedal cranks.

602

[agg221]

I once had the same sort of argument in a cycle shop, a fairly large family owned shop. The owners son was insistent that there was only one type of thread used on a bike, Metric, even thou my bike was a 1960's BSA. After I'd had a few words about him not having knowledge of what he was selling, his dad came and served me with the correct parts.

There used to be a second hand tool stall at Saffron Walden market on Saturdays. The stallholder bought up job lots from wherever and brought the whole stock in a trailer and van each Saturday, displaying the higher quality tools but anything a bit unusual and bulky he really couldn't be bothered with and sold cheap to stop having to lug it around. I picked up a 5t Tirfor winch complete with long cable for £50 for that reason! He absolutely couldn't be bothered to pick through and sort all the taps and dies, so they just got chucked in boxes.

One Saturday, I had nothing better to do while my wife went off to something or other, and sort of fell in to sorting the lot. I was well through it before the market closed up for the day, so I took all the unsorted ones home and finished them off - taking them all back the following Saturday. In exchange, I ended up with a full set of BSC, a full set of BA and as many bits of UNC/UNS/UNF as I could find, for the princely sum of a tenner.

I still haven't used the BSC for anything, but they might come in useful one day!

Alec

[Calum]

I've just been stocking up on BSC taps and dies (sometimes also called CEI- cycle engineers' institute I think) for my BSA and my other half's Ariel. BSC also gets confusing as some manufacturers went to 20tpi above 7/16" and some didn't  they are also 60 degrees not 55 as other British standard threads.

BSB is another uncommon one now - I think they are 26tpi too from memory, all sizes. Originally for brass conduit where the wall thickness of the brass tube stayed the same for all diameters and hence the tpi remained constant also. I seem to think some Lucas spotlights mount on BSB threads. Then there was another British standard conduit altogether 

[agg221]

BSB is another uncommon one now - I think they are 26tpi too from memory, all sizes. Originally for brass conduit where the wall thickness of the brass tube stayed the same for all diameters and hence the tpi remained constant also. I seem to think some Lucas spotlights mount on BSB threads. Then there was another British standard conduit altogether 

Yes, I ended up with some BSB in there too I think. All utterly random and may well never get used but you know if you don't have it you will want it. Sadly I didn't turn up a pair of LH and RH thread 11/16" UNF; one of the most one-off use sizes imaginable I suspect, but I do actually need them, having had my track rods galvanised.

Alec

[Davidss]

... Sadly I didn't turn up a pair of LH and RH thread 11/16" UNF; one of the most one-off use sizes imaginable I suspect, but I do actually need them, having had my track rods galvanised.

I cannot immediately think where to get an authoritive verification, but my recall is that LR Series track rod ends are UNS not UNF.

Regards.

[autorover1]

Tracy Tools have LH taps https://www.tracytools.com/taps-and-dies