Nut Sizes

[JohnnyT]

What nut bolt system was used on late 50/early 60s Triumphs? I have a Tigress scooter and cant work out what system was used.I have a front wheel nut which is 0.9 inches 23.3 mm which is apparently 1/2 inch whitworth. Got a whitworth socket set(modern) and the 1/2 socket wont fit. Is this because its modern? Ive heard they dont fit older nuts. This has been one of the biggest delays of the whole project.

[cardan]

Sigh - sometimes it isn't easy!

The only difference between "old" and "new" whitworth hexagons is that the early ones have one size larger hexagon. i.e. an old (say pre WW1) 1/2 W nut has the same size hex (0.920" AF - across flats) as a post WW2 9/16 W nut. Spanners and sockets are often labelled 1/2W-9/16BS to reflect this.

Thus "whitworth" tools fit old or new "whitworth" hexagons.

More-or-less there are only three options for hexagons, which are always measured AF (across the flats): imperial (labelled AF, where 7/8"AF means 7/8" across the flats. Similarly metric is measured AF, so 21mm is 21 mm across the flats.

Only Whitworth/British Standard have "silly" AF measurements, which can be googled.

(I'm not going to mention BA hexagons! Luckily these are small, and not used on axles.)

Good luck!

Leon

[Rex]

Sigh - sometimes it isn't easy!

: imperial (labelled AF, where 7/8"AF means 7/8" across the flats.

If a spanner was labelled 7/8 AF it would be for a Unified (SAE) threadform, not Imperial, and unless the OP had a post 1968 Triumph, BSA or early H-D it wouldn't fit the fasteners.
Imperial threads are BSW,BSF,BSCY, BSP etc. and those are what was used on most British bikes.

[R]

Hang on to that set of whitworth sockets !
You'll need them.....

1/2" W is actually quite a large nut.
The next size up/down should fit it ?

As mentioned, BS (British Standard) sockets and spanners will fit, although they are branded as one size different to W sizes.
So 3/8W is also 7/16 BS, for example.

Someone hasn't bodged it with the wrong nut, have they ?

[john.k]

Wheel and axle nuts are often odd sizes for serviceability ,and so the cheap tube spanner in the toolkit wont bust first time you get a flat tire....I find with a selection of metric,AF and W /BS tools I can fit almost anything......For instance ,the Norton laydown box has a casing nut requiring a very thinwall socket........doubtless the original tool was a tube spanner.....Period pictures of factory assemblers show stacks of tube spanners beside the bikes................obviously better quality than those in the bike toolkit.

[cardan]

Sigh - sometimes it isn't easy!

: imperial (labelled AF, where 7/8"AF means 7/8" across the flats.

If a spanner was labelled 7/8 AF it would be for a Unified (SAE) threadform, not Imperial, and unless the OP had a post 1968 Triumph, BSA or early H-D it wouldn't fit the fasteners.

Well, not really. Hexagon sizes and threads are very often unrelated. Believe it or not, pre-WW1 Belgium-built FN motorcycles used all their own threads - unlike anything else but of imperial diameters (1/4-22, 5/16-20, 3/8-18 and other weird things), with imperial hexagons (7/16"AF, 1/2"AF etc.)

I have an Australian-made motorcycle and most of the fasteners have BSW threads, but with imperial hexagons.

As I noted above, AF just means "across flats" and does not make any comment on the thread to be found on the fastener.

It's all good fun!

Leon

[john.k]

FN used a lot of existing gun fitting threads.....for instance the 1/4" x 22 thread is from the two triggerguard screws of the 1889 Mauser rifle that FN was set up to make.All the machines and tooling were supplied by Ludwig Loewe of Berlin,who were also variously part owners ,mortgagees in possession,and finally all the machinery was repo ed in 1914 to form a fifth production facility in Berlin at DWM......then all grabbed back again in 1919,with Loewes dispossessed permanently as they were jewish ,however DWM seized the plant again in 1939,and used the FN military bike as a model for the BMW sidecar wheel drive.

[cardan]

FN used a lot of existing gun fitting threads.....for instance the 1/4" x 22 thread is from the two triggerguard screws of the 1889 Mauser rifle that FN was set up to make.

Thanks John - I hadn't heard the story about the machinery before. The various histories of FN are pretty quiet about what happened in Liege during the two wars...

The 3/16 thread used by FN is 3/16-30, still used to secure the grip on a pistol!

Cheers

Leon

[Rex]

As I noted above, AF just means "across flats" and does not make any comment on the thread to be found on the fastener.

Leon

AF does indeed stand for "across flats" but you won't find that nomenclature on any Imperial spanners (often incorrectly termed "Whitworth") but you will find it on spanners intended for use on SAE threaded machinery.
This is obviously for the generally available tools and not specialised "ah yeah but in 1935 Spagthorpe made a tool kit for the Whippet...etc etc" stuff.

[iansoady]

This is quite a good exposition if rather long and US-biased: http://progress-is-fine.blogspot.com/2017/01/the-evolution-of-standard-wrench-sizes.html?m=1

[TGR90B]

I always thought AF stood for American fread.

[mini-me]

Far too many odd nuts on here

[TGR90B]

It's true though, that's what always what came to mind, Anyhow, isn't it time for your lunchtime tablets?

[mini-me]

this lot are for  breakfast and tea time.

[murdo]

Too many thread and pitch sizes, no I'm really confused.