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

What is the reason please.

Steve

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

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

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.

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?

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.

Re: Square Nuts

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

… but the Plant's advert is unambiguous.

MichaelG.

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.

"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."

The opposite is also true, early Lancia cars had Unified threads with Metric head sizes, presumably for the same reasons.

chriStephens

Square nuts on cast iron gutters are a nuisance when you put them on the wrong way round but balancing up a ladder in some contorted position to reach it is an achievement to get the thing on without dropping it let alone get it on the right way round.

Other fun engineering errors are serrated washers with plain washer too, 'wrinkle' or 'wavey' washers except on no-spanner electrical connections.

I wonder if in Planet of the Apes all the monkey engineers put the big nut over the little nut?