Author Topic: Threads and hex sizes, '59 A10 RR Footpeg stud  (Read 807 times)

Offline KeithJ

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Foot peg retaining stud is 1/2" dia with a 20 tpi thread.  Is that 1/2" x 20 tpi BSCY and if so, why is the hex size on the nuts 0.790 A/F when the standard "Whiit" hex is 0.820 A/F?
'59 A10RR + Second engine

Offline Beezageezauk

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #1 on: 11.02. 2014 17:12 »
Hi Keith,

You question prompted me to check out Lightning Spares' Catalogue as they specialise in replacement fasteners for BSAs.  On their Cycle Thread page they list 26tpi and 20tpi nuts with standard size across the flats and 26tpi and 20tpi with reduced size across the flats.

Because of this I presume that BSA used reduced sized fittings for various applications. with foot peg retaining nuts probably being one of those applications.

Beezageezauk.


Offline KeithJ

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #2 on: 11.02. 2014 18:21 »
Hi Keith,

You question prompted me to check out Lightning Spares' Catalogue as they specialise in replacement fasteners for BSAs.  On their Cycle Thread page they list 26tpi and 20tpi nuts with standard size across the flats and 26tpi and 20tpi with reduced size across the flats.

Because of this I presume that BSA used reduced sized fittings for various applications. with foot peg retaining nuts probably being one of those applications.

Beezageezauk.
I've had the bike for umpteen years and believe the "nuts" were original fitment.  I am guessing the hex is an A/F standard.  Would be interested to know if my "undersize hexes" are were standard.  Always wonders why my Whit spanners did not fit.  Is one of the nuts a fixed one or are they both free ones?
ATB

Keith
'59 A10RR + Second engine

Offline trevinoz

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #3 on: 11.02. 2014 20:32 »
There are a few nuts which are 25/32" AF.
Another one is on the crankshaft.
Spanners are about but not readily.

Trev.

Offline Beezageezauk

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #4 on: 11.02. 2014 20:33 »
Yes Keith the nuts are standard.

I believe that the footrest retaining stud is part number 42-4855 and if I remember correctly it is a 1/2inch diameter round threaded with 1/2" cycle thread (20TPI) both ends.  I also seem to remember that it has a nut brazed onto one end.

The other end has a plain washer and a locking washer with a nut (part number 2-124).  I have a list of standard nuts that BSA used and part number 2-124 shows it as being a 1/2inch CEI X 20TPI nut, 0.203 inch thick and 0.782 inch across the flats.

So what you have appears to be correct.

Oh yes,  FYI:- the stud type bolt, for want of a description, should be 11 3/4 inches long....anyway, that's the information I have.  Hope it helps.

Beezageezauk.

Offline KeithJ

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #5 on: 11.02. 2014 21:03 »
Thank you for the posts, very informative.  Trying to understand why an odd size hex should be used.   Any thoughts?
'59 A10RR + Second engine

Offline chaterlea25

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #6 on: 11.02. 2014 21:25 »
Hi All,
I wonder if the reduced head is used because there is limited room for a spanner or socket 
especially with the later type footrests where the nuts are under the mounting boss  *????* *????*

Regards
John
1961 Super Rocket
1963 RGS (ongoing)

Offline KeithJ

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #7 on: 11.02. 2014 22:24 »
There are a few nuts which are 25/32" AF.
Another one is on the crankshaft.
Spanners are about but not readily.

Trev.
25/32 = 0.781.  My hex's measure 0.790 doesn't appear to be 25/32?  20mm (0.787") perhaps?
What spanner have others used?  I can only recall getting an open jaw on it.  Will check a metric socket though.
'59 A10RR + Second engine

Offline trevinoz

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Re: Threads and hex sizes, '59 A10 RR Footpeg stud
« Reply #8 on: 12.02. 2014 20:25 »
I use 25/32".

Trev.