headbolts

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Jul 11, 2007
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HI
I'm pulling the head off my new project bike 69 750 Norton a 13 mil is to small for the head bolts and a 14 mil is to big so i thought I would try a 1/2 in. it was to small and a 9/16 is to big, what size it. Any body run into this problem. The guy I bought the bike off of is just packing up to move and has'nt come across the shop manual yet.

Rockin
 

L.A.B.

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Not really a 'problem', some Norton hexagons are Whitworth (BSW) size, as a lot of Norton fasteners were originally BSW/BSF/BA/CEI threads. Although many of the thread forms were eventually changed to US SAE UNF/UNC the Whitworth hexagon sizes were retained for certain fasteners.
This may seem a bit odd (to Americans anyway who grew up with SAE) but in the UK and other Commonwealth countries British Standard size tools were far more common around that time.
So the head bolt hexagon size is = 1/4" Whitworth, the hexagon size being 0.525".


http://www.timebus.co.uk/rlh/whitworth.htm
 
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Nov 18, 2005
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For the nut at the rear of the head you'll probably need a 1/4 whitworth ring spanner with the ring ground thinner . That's the only way I know of getting enough motion on the nut.

For the recessed nuts in the front of the head I use a 13mm box spanner with a socket on the other end. It seems box spanners are not made to the same tolerance ( ie they are a bit looser) than sockets or ring spanners.
 
Joined
Jul 11, 2007
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6
head bolts

Thanks for the lesson in British nuts and bolt sizes. I stopped at the guy I bought the bike from to pick up some lumber I'd also bought from him and as I was loading the lumber he come out with a set of british spanners and sockets, he said these go with the bike forgot to give them to you so, that made my day, the set is missing the 1/4w socket but he said it was there someplace hopefully he will find it and I will be set.

Thanks Rockin
 
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