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Nut and Bolt sizes on T/S6 motors

Started by kmd, 11 Aug 2008 at 15:13

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Hi All

Can any help me with the sizes of the nuts and bolts on the T/S6 Engine?
I think they are 25tpi but they seem to come out really odd sizes,
Good old Mr Douglas?

Many Thanks


Hi Kevin
    The most common bolt size on the 1930s models relating to cylinder head nuts and studs etc. is the 5/16" x 25tpi. There are also examples of the other Douglas special thread size of 17/64" x 25tpi. Taps and dies for these sizes are held in pre-1939 Spares by the LDMCC. You may also find examples of 1/8" and 1/4" BSP and another odd size used on oil and petrol unions being 7/16" x 19tpi. The carburettor base connection on many carburettors is 9/16" x 20tpi. Some timing cover screws are 3/16" x 27tpi. Again taps are kept by LDMCC for this size. Even where standard Whitworth threads are used Douglas often selected the non approved sizes such as 7/32" x 24tpi screws  used on many pre-1939 flat tank models for holding the petrol tank to the top tube. I am sure it was all part of Mr Douglas' plan to ensure that if you wanted spares for your Douglas, even down to a nut, you had to buy them from him.



Thats a great help.