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Nut Sizes

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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:

--- Quote from: cardan on December 03, 2018, 09:12:38 PM ---Sigh - sometimes it isn't easy!

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

--- End quote ---

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.

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