Author Topic: Banjo bolt sizing  (Read 3056 times)

Online lawnmowerman

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Banjo bolt sizing
« on: 20.04. 2012 15:54 »
OK hands up, it's not from a BSA but I am hoping someone can help identify the size of this banjo bolt so I can order some.

It is from a 1938 Wolseley and they are used on the Lockheed brake wheel cylinders. They probably had not been taken out for 74 years and I butchered the heads on two of them.
 
Thanks
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Offline bonny

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Re: Banjo bolt sizing
« Reply #1 on: 20.04. 2012 16:33 »
7/16" sae (society of automobile engineers) standard (sae std) ? This is 20 tpi for 7/16".

Online lawnmowerman

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Re: Banjo bolt sizing
« Reply #2 on: 20.04. 2012 16:40 »
Thanks Bonny. I spent about an hour on the net looking up thread size charts and gave up and had a beer!

Jim
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Offline bonny

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Re: Banjo bolt sizing
« Reply #3 on: 20.04. 2012 16:46 »
Handy chart here.    http://mdmetric.com/tech/tic1d.htm

Or engineers toolbox website is invaluable too.

http://www.engineeringtoolbox.com/

Offline Beezageezauk

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Re: Banjo bolt sizing
« Reply #4 on: 20.04. 2012 16:56 »
Jim

7/16 X 20tpi could be one of a couple of threadforms.  Favourites would be cycle thread (CEI) or UNF.  Both are very similar but I don't know if they are interchangeable.  I would guess, if it's from an old British car, that it would be cycle thread.  UNF, at that time was predominantly used on the American market.  Note that 7/16 cycle thread is also available with 26TPI.

Ok, on stating the above, I'm no expert with thread forms and others on this forum will probably have much more knowlege than me on the subject.

I know that the British cars from the 1970's and 80's used a 7/16 x 20 thread on their seat belt anchorages but the bolts were threaded all the way down so couldn't be modified to suit your purpose.  You could maybe check the thread if you have one kicking about.  I have a couple here.  If you want to try one send me a PM with your address and I'll put one in the post for you.

At least it would be a start.

Beezageezauk.

Offline bonny

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Re: Banjo bolt sizing
« Reply #5 on: 20.04. 2012 17:12 »
It shouldn't actually matter what thread form it is , you have the major diameter and the pitch , so anyone with a lathe should be able to turn you up a couple. But it think beezageezer is correct  , sae and unf became the same after the war or sometime around then.

The old book of threads (1919) i have doesn't list any details between 3/8" and 9/16" for cycle , suggesting there is a duplicate in some other form , eg. Sae or unf, no 7/16" cycle listed, but 9/16" has 20 tpi so its a good bet 7/16" is 20 threads too.

Online lawnmowerman

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Re: Banjo bolt sizing
« Reply #6 on: 20.04. 2012 19:18 »
Thanks guys. Why is life so difficult?

I had a look at SAE on the web and yes, it looks like it changed to UNF.

I think it would be unlikely to be a cycle thread being as it is on a car. The confusing thing is that some parts seem to be Whitworth / BSF and others are metric (strange for a British pre-war car).

It is from a Lockheed brake system and I think Lockheed are / were an American company so may explain the SAE origin.

A 3/8 W 7/16 BSF spanner fits the head.

I will probably try to dress the damaged heads with a file so that I can get a good fit with a smaller metric spanner or an adjustable. Either that or try to get some NOS or used ones from a classic car spares dealer.

PS. Bonny. The MD metric size table is useful and based on the major diameter it certainly looks like a 7/16 UNF 20 TPI bolt with the head turned down to create the shoulder which engages the banjo union top.

Thanks for the offer of the bolt Beeza. I may take you up on it when I get the cylinders back which are being resleeved in stainless at the moment.

Jim

1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Online chaterlea25

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Re: Banjo bolt sizing
« Reply #7 on: 20.04. 2012 22:52 »
HI Lawnmowerman,
Correct!! the reason the threads are 20 tpi (UNF) is that they are made under Lockheed patents
Even some Japanese brake caliper pistons from the 80's were made in inch sizes *ex*
Regards
John O R
1961 Super Rocket
1963 RGS (ongoing)