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25-02-2022, 11:27 AM
(This post was last modified: 25-02-2022, 11:28 AM by Dennis Nicholas.)
Just measured thread with Whitworth thread gauge and it is 16 threads per inch.
Diameter of thread is 0.621 with my micrometer (which is nearly 0.625 inch = 5/8 inch.
My Austin nut across flats measures 13/16 inch by calliper (0.8125 inch). (note 7/16 given in my table as 0.82 AF).
Ah just seen table someone made........stub axle bearing nut 5/8 inch Austin special 16 tpi whitworth form...55 degree thread angle.
I note that 7/16W is slightly larger (0.82 inch) spanner size than 13/16 but would do?
Dennis
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Car type: '28 GE Cup. '28 AD Chummy '30 RL Saloon. '34 RP Saloon. Too Many toys!
Dennis.
I wouldn't get over worried about what 'standard' the threads and nut sizes are on an Austin 7. Frankly many are not.
For threads measure major diameter & TPI. They will be whit form on the mechanical components.
The spanner size of the nuts all confirm to Whit standard, and a tool marked 7/16W is the tool for the job here. As noted a spark plug socket works fine. As does an adjustable....
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Dennis,
a 7/16W multipoint socket fits the outside of the nut you are talking about - if you thin it down it will fit with the outer hub still on.
The thread inside this nut is the special 5/8" x 16 tpi used on the half shafts, radius arm ends and possibly elsewhere.
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Many of the posts on Girling hubs adjacent are relevant.
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An attempt to summarise.
First a little bit of terminology which can cloud issues. A spanner I recognise as a bar of metal with either an open ended jaw at the end or a closed ring. A box spanner being a round tube of metal shaped into 6 flat sided shapes at each end.
Sockets can have their size shown as the measurement across the opposite flats (AF} (More modern socket sets) - OR - the size of the nut they fit.
A nut size is usually given as the diameter of the round bit it screws onto.
The Austin 7 front stub axle has a diameter of thread of 5/8 inches but is a non standard 16 Threads Per Inch (TPI) the form (shape) of the thread being Whitworth with its 55 degree thread angle.
Hence the nut is a 5/8 inch but with a non standard 16 TPI thread. The distance across 2 opposite flats of the 5/8 inch nut is 13/16 inch.
A socket marked 7/16 W (whitworth) can also have the marking 1/2 BS(F)......measuring across the 2 parallel opposite internal flats will give 13/16 inch - the size of the 5/8 nut.
A modern (American terminology) socket marked 13/16 gives the across-the-flats size so is one to use. (my such socket fits nicely in the end of the hub).
A 14mm plug socket measures across the flats as 13/16 inch and is often the thiner diameter hence is good to use.
13/16 inch (0.8125 inches) is 20.6375 mm so nearly 21mm so a socket marked 21mm would also fit our nut but rather slack while a 20 mm socket would not go on.
Dennis
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Hi
The information I have suggests that unlike Unified fasteners, the dimension across the flats for the BSF and Whitworth ranges of nuts don't correspond to an exact fraction of an inch
For the nut in question, the head size is likely to be 0.820 inches or 20.83 mm. For standard fasteners this would be the head size associated with 1/2 inch BSF or pre-war 7/16 inch Whitworth. So it looks as though Austin specified a smaller than usual head as well as a different TPI.
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I think non standard threads are often adopted to lessen the chance of some mild steel substitute which may not be adequate. Using a micrometer or vernier calliper and finishing 3 adjacent flats first, hexagaons can be file reduced or made with considerable accuracy.
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Yes John, looks like it. Using a micrometer (which may not be necessarily 100% accurate) I got different readings round the different faces - 0.8155, 0.817, 0.8183 and the calliper showing just about on 13/16.
Still good enough for a socket fit.
Dennis
