Victorian Whitworth nuts.

The British standard for Whitworth nut sizes famously changed mid 20th C to the smaller size used for BSF, which size curiously also appears for coarse threads on at least some Victorian machinery. Does anyone know if this practice was common, or perhaps even Sir Joseph's original standard, leading to the irony that modern nuts are actually the "correct" replacement.

Perhaps there was even a choice of the two.

If anybody who works on old machinery has anything to say I'd love to know- I'm currently drawing an 1855 marine engine whose fasteners have disintegrated but it seems there is only space for the smaller size.

Ps by old I mean 19thC before the first BS of 1908.

Edited By jonathan heppel on 07/06/2014 15:20:28

I think you will find that the size of some nuts on some old machinery was made to fit the space by individual makers. The thing I have with nuts of this vintage is the square ones, people put them on up side down ie., flat side down, chamfer up, where as it should be the other way. Ian S C

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Very true Ian, for obvious engineering reasons.

... Trouble is; it looks "wrong" when done right.

... Perhaps a tiny chamfer on the four top edges would help.

MichaelG.

What is the reason please.

Steve

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The turned chamfer acts a bit like a washer ... but if the nut is flat square down, it needs a big spot-face [at least the diagonal of the nut] if it's not going to dig into the casting.

MichaelG.

The hexagon sizes were changed at the start of WW2 as a material saving measure.

I have some old , not sure how old but pre -war, agricultural bits with square nuts. These have heavy chamfers, almost coned, with the flat face down and washers fitted.

Thanks for the replies. The Whitworth Society is looking into it for me but I thought there might be some members here with personal experience. They did tell me of an early 7/8W bolt with a 13/16" BS nut so I feel a bit more digging will confirm my suspicions that the practice (if not formal standard) changed twice.

Ian S C I agree with you up to a point but considering Sir Joseph's zeal for standardising and this being a high tech RN warship engine they will have been made to an existing standard. There are some surviving yellow metal small head nuts but since they are ratchet specials it's unwise to draw conclusions.

If true it does have implications for scale modellers, of course.

Ps I should have said that they are all hexagons.

Edited By jonathan heppel on 08/06/2014 16:30:17

Thanks MichaelG. I did not know that.

There is a victorian engine in the South Ken museum (the 1882 Webb restoration of a Trevithick engine (maybe the 1806 dredger ) that has square nuts (they look like they are unchamfered) with washers under. Now I know why.

Steve

The bodywork on pre-war motorcars often relies on old-size, square, WW nuts on carriage bolts (etc), and in my experience, always fitted flat down, chamfer up, on a washer. And I surmise that they knew what they were doing. At the same time, many bolts were being made without a chamfer below the head, or a washer-face.

My understanding of the original designs was that they were standard bolts for engineering - and primarily, civil engineering, which is why they go to such large sizes. Such fasteners were out in the rain, very often, and were being maintained by yokels, and always with open-enders (or worse), so big square heads were quite sensible.

And some firms used the next size down again, where clearance is an issue - eg Norton twin cylinder base nuts.

Cheers, Tim

Edited By Tim Stevens on 08/06/2014 16:42:47

Yes Tim that's definitely the Gucci way of doing it- arguably the "proper". Thing is, washers get lost, in which case plan B. Thanks for the next size down tip- I didn't think there was room.

While on the size of nuts - early Morris cars used metric threads throughout the engine but they were fitted with Whitworth size nuts. Presumably so that garages could use their existing spanners.

Much different to the situation now where almost every new car needs a number of special tools.

Russell.

> If true it does have implications for scale modellers, of course.

I am making a model to an old engraving that shows very chunky nuts on relatively slender studs. As far as I can tell the rest of the dimensions are accurate so I'm using 'not one size smaller' nuts to better match the engraving.

Neil

I don't know whether this should be posted under a different heading, but I would like to ask about the correct fitting of locknuts in older times, before adhesives, aero nuts, stiffnuts etc?

It seems obvious that the slimmer nut simply locks by friction to the lower one. But, by doing so, also it relieves some of the pressure on the flanks of the lower one.

Many years ago there was some disagreement in the letters pages of M E; some said that the (usually slimmer) locknut should be put on first ie the first to be tightened, with the deeper nut tightened down onto it. Presumably the theory is that the upper, thicker, nut screws down so tightly that that pressure on the slim nut is relieved or even reversed.

Anyone have any thoughts about this?

If you can find the back issues, I think Tom Walshaw/Tubal Cain put the 'matter to bed' in great detail with some logic and some stress diagrams. It would be nice to see a modern computer simulation of the stresses for the two arrangements.

Neil

In the real world outside of modelling I have never seen the little nut on the bottom. Clamping loads is quite a complex subject and calculating the correct torque for any bolt/stud is not a simple calculation. If you were trying to get the correct tension in the bolt/stud because that is what you are trying to achieve if you have the little one on the bottom the chances are you would strip the threads out of the thin nut.

Back on the subject I have seen square nuts on old agricultural machinery and they were domed on the upper face and larger than one would expect to see.

It all boils down to which nut is resisting the load, and which is pushing in the direction of the load. With a thin locknut on the outside all the load is taken by this nut (and its shorter engagement). If this outer nut is tightened properly, the 'slack' in the inner nut is pushed together, making the other side slack. This can overload the thin nut. Put the thin nut on first, and you have the thicker nut doing the work.

More recent work tends to show that if the design is sound, the bolt is dead straight, and the nuts are threaded at right angles to the face, and both clamped surfaces are parallel and at right angles to the bolt, a properly tightened nut will stay tight. On its own, relying on friction, nothing more.

Cheers, tim

Re: Square Nuts

Interesting to see that this page illustrates both orientations of square nuts

... but the Plant's advert is unambiguous.

MichaelG.

I remember sore and lost knuckles from trying to undo some on old textile machinery, ouch!

Brian

Hi Michael, I believe that being how square nuts were very often used without washers or the likes of spring, shakeproof washers ect., it helped them from working loose.

I guess a lot of British industry must have got things wrong as just about every square nut that I have ever seen has had the flat face downwards, and that includes both factory fitted and in old steel structures that I've worked on.

At the bottom of my garden there is an old dissused industrial siding from what was once a main line, where there is the remains of an old open railway wagon, the timbers have all rotted away as it has been laying there for over 40 years and there is what is left of the bolts still in the holes with flat nuts with the flat side down.

There is also an old rail shoe with the bolt and square nut with the flat side down, the sleeper long since rotted away.

In the top picture the bolts were 3/4" and the nuts were 1-3/8" across the flats and on the rail shoe the bolt is 7/8" and the nut is 1-5/16", I don't know what thread they are, but look course enough to be Whitworth.

Regards Nick.