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Part 37: Nut and bolt

The most common Meccano part by far, of course.  It doesn't bear thinking about how many millions upon millions of these were produced, only to be eaten by the hoover.

Meccano nuts and bolts work to a fairly unusual thread pattern, known as 5/32'' Whitworth. The most significant use of these bolts at the time was to attach door knobs to their spindles, which is rather useful to know if you have a house of around that vintage! It was probably chosen as the nearest commonly available mass-produced size that would comfortably fit in the holes governed by the 8swg axle size.

There's a lot more to the humble nut and bolt than you might think, as we will discover...

37Nut and bolt 1901-59400
37aNut 191219736630730N°00
37bBolt 1920-0624680N°00
37cHex nut 1973-
Loading picture Nutsandbolts

The parts

Four part numbers are on this page, although one of them is a 'combined' part.  Part 37 is a nut and bolt, consisting of a part 37a (nut) and part 37b (bolt).  The table above is slightly confusing in this respect, as they were originally referred to in pairs until the 30s, when they started being counted independently.  Meccano outfits generally contain a few more nuts than bolts (to allow for lock-nutting).

To be absolutely correct, only the 'nut and bolt' existed until around 1912/13, when part 37a (the first part with a suffix) was first mentioned as a part available on its own.  It wasn't until around 1920 that part 37b was also mentioned and available for sale.  As you can see from the table above, even as late as 1929 outfits were considered to include a number of part 37 and a few extra 37a's.

Starting from the beginning of 1973 with the first Multikits, the square nut was replaced by the hexagonal nut, part 37c.  Part 37 thus became a part 37c (hex nut) plus a part 37b (bolt), and part 37a was discontinued.  Part 37c replaced 37a in all outfits during 1973.

Chronological variations

Standard and 'thin' nuts
Loading picture Nutthickness Initially, there was only one length of bolt in the Meccano system, around 5/16" (9mm) of thread plus the head.  The length was needed because of the thickness of the folded-over MME strips, but caused no end of irritation as two bolts would interfere with each other if both were run into an angle bracket or girder.  The earliest ones are easy to identify with a magnet -- they're solid brass and all subsequent Meccano nuts and bolts were plated steel.

Finally, in 1919, the first 'long' bolt, the ¾'' part 111, was introduced.  In 1922, the new 'short' bolt of 7/32'' was introduced as part number 111b, and somewhere between 1924 and 1926 this took over part number 37 and 37b as the standard size of bolt. Further discussion on this transition between 111b and 37 is described on the Long bolts page here.

A short-lived 'economy' thin nut was produced during WW1, and the comparison is shown here.  These are very weak and as they only hold one thread, difficult to use.  They are often found broken in two.

Pre-war and post-war cheesehead bolt types
Loading picture Boltheads The 'standard' brass-plated cheesehead bolt is often thought of as one long-lived part, but there is a distinct difference between the pre-war and post-war varieties.  The pre-war has much sharper corners to the head, whereas the post-war is noticeably chamfered.  This has one useful side-effect when dating and identifying nuts and bolts: the blackened steel bolts from the Mechanised Army outfits (1939-41) are also sharper edged than the post-war Korean economy (1951-52) and Army Multikit (1973-1977) black bolts.  This is a good way of identifying whether nuts and bolts included with a Mechanised Army outfit belong there.

There was a change to dome-head bolts in 1929, lasting until 1933 when the cheese-head bolts returned.

During the Korean War shortage of brass and steel, economy nuts were made of a lower-grade steel and are not only black but also extremely brittle and break in two when tightened.  Nuts and bolts of this period were supplied in boxes and envelopes with a turquoise sticker and broken black band to identify that they are blackened steel parts.

Variations and oddities

Often confused with this part, the set screw (part 69) is shorter and has a much smaller head, but it does come in many of the same variations.

Dealer spare parts boxes

Loading picture Nutboltspare

As one of the most critical and losable parts in Meccano, there was always a strong demand for spare nuts and bolts.  These were originally in small boxes like the ones top left (dating from around the mid-20s), and then later moved to the small brass-plated tins with paper labels seen top right.

Post-war morphine tin and pre-war gross of part 37
This image does not belong to the webmasters and is copyright.
Please do not download or copy it for any purpose. It has been
kindly provided for use on this site by the image owner,
Staffan Kjellin
Loading picture nutboltspareparts2

By the end of the 1920s, as well as buying the tins containing a dozen nuts and bolts, there was also a part 37F tin containing 50 nuts and bolts as in the photo above (F stands for fifty), and a 37G containing 144 of each (G standing for gross), shown right.  Both of these tins contain dome-head bolts and are therefore likely to be 1929-1932.

The photo to the right also shows the immediate post-war spare parts tin of nuts and bolts. Note that they are packed in spare morphine ampoule tins (as manufactured by the Meccano factory during the war), and have pre-war cross-hatching on the labels but post-war "Made in England" printed on them.

After this, the standard boxes take over, and now nuts and bolts are available in boxes of two dozen at a time, and also individually as parts 37a and 37b (centre of picture).  These continued into plastic bags in the 60s and 70s with various labels.  Both the blue label and white label bags contain zinc plated square nuts and bolts.

Individual part numbers

Part numbers for the parts on this page are as follows:    Unique part numbers
For identification, each variation has been given a suffix to the main Meccano part number. These suffixes consist of a two-character code for the colour, and if there are many variations, a further number and sometimes letter code to identify each variation. See the bottom of the 'Parts' page for further details.

You don't need to worry what the codes are, just click on any one for a photograph.

The button above turns on and off the display of DMS numbers (where they are known). The DMS (Development of the Meccano System, Hauton and Hindemarsh) published in 1972 and added to in 75 and 82, suggested part numbers for every variation of every Meccano part. These numbers aren't perfect, but they are recognised and also referenced in the EMP (Encyclopedia of Meccano Parts, Don Blakeborough).

More about bosses More about stampings More about paint colours
(measurements given are approx thread length EXCLUDING head.  Where not given, length is approx 5.5mm = 7/32'')
Brass, 9mm, deep cheese head 01.mm.mm.mm 
Nickelled steel, 8mm, cheese head 08.ni1.ni1.ni1 
Brass plated steel, 8mm, shallower cheese head 12?.br1.br1.br1 
WW1 'economy' nut, thinner † 15? .br2  
Cheese head, sharp edges, brass plated 23-.br4.br.br4 
Dome headed, 5-6mm, brass plated 29-32.br3.br3.br3 
Nickel dome head bolts for digger bucket †¹ 28-40.ni2.ni2.ni2 
Cheese head, sharp edges, brass plated (see above) 33-41.br4.br.br4 
Cheese head, sharp edges, black (Mech.A) † 39-41.ma.ma.ma 
Cheese head, brass plated 45.br.br.br 
Cheese head, black (Korean) † 51-52.bs.bs.bs 
Cheese head, zinc plated 66.zn.zn.zn 
Cheese head, black with hex nut (Army/Combat) † 73.bs1 .bs1.bs
Cheese head, zinc plated with hex nut 73.zn1 .zn.zn
Cheese head, brass with hex nut (Highway) † 74.br5 .br.br
Round head, brass with hex nut 78.br6 .br6.br
Round head, black with hex nut (Army/Combat) † 78.bs2 .bs2.bs
Round head, iridescent with hex nut 79.ir .ir.ir
Round head, zinc with hex nut 79.zn2 .zn2.zn
¹ Nickel-plated dome head bolts continued in Aero outfits until 1941.
Nickel-plated nuts and bolts did not exist in the 1960s – brass nuts and bolts continued into the silver/yellow/black era until they were replaced by zinc plated bolts.

Please send us pictures of missing parts! Hints and tips for pictures
Take a picture of the part in very good light, preferably on a plain yellow background, without a flash but with a tripod.
Ideally, trim the picture to about 150 pixels per inch of the Meccano part (unless the part is particularly big or small), save it as a reasonably good quality jpg file with a filename of exactly the part number, for example 19b.ni1.jpg, and email it to us by clicking on 'Contact us' at the top of the page. Thanks!

Further information

Total number of messages on this page: 25.  This is page 2 of 5.   Previous  Next

Greg Judd      (at 4:53pm, Fri 30th Aug, 13)

I have just opened my old box of childhood meccano for my son to play with. Everything is in perfect condition except that all of the '37' brass nuts and bolts are missing! So frustrating! Are you able to help please? Would you be able to supply me with x100? If so, how much?
Thank you very much.
Kind regards,

Greg Judd      (at 4:48pm, Fri 30th Aug, 13)

I have just opened my old box of childhood meccano for my son to play with. Everything is in perfect condition except that all of the '37' brass nuts and bolts are missing! So frustrating! Are you able to help please? Would you be able to supply me with x100? If so, how much?
Thank you very much.
Kind regards,

Colin Smith      (at 7:03pm, Fri 23rd Sep, 11)

Whilst I agree that in 1913 the first a suffix parts were shown, as far as I can see there was 37a Nut and 57a Scientific Hook. However in the Meccano America parts list from 1911 there were already 13a 8" Axle Rod, 15a 4.5" Axle Rod and 22a Pulley without Boss.

Colin Smith      (at 12:01pm, Thu 18th Aug, 11)

I have a bag of black round heads with square zinc nuts.

Barry Gerdes      (at 5:10pm, Sun 27th Mar, 11)

The "hex pegs" in "round holes" mentioned by Terry is a recurring problem with many bolts and cheap allen keys that have a much larger tolerance in size than the should have.

I have a solution that works in a lot of cases. I have one of those 100+ scewdriver kits and amongst the adaptors there are a few hex star keys. Now it just happens that some of these star keys can have the sharp points pushed (jammed) into what is left of the corners of the allen key slots. This trick has helped me to salvage many items that would have otherwise need to be discarded.

kbisset      (at 7:18am, Sun 27th Mar, 11)

To throw a spanner into the works - US Meccano used a #7-32 ASME thread from around 1921 (+/- a year) until about 1929. The whole story, including a paper with excruciating detail, is at:


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