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Dec 14, 2019, 07:37 PM
mcintmg's Avatar
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Thread size for K-Mills .75 crankshaft

Does anyone know what the thread size is on the crankshaft of an Aurora K-Mills .75?
I need to tap a new spinner nut and don't know the thread size?

It is not Metric. I tried a 4mm and 3.5 mm nut and the 4mm is too big. the 3.5mm nut starts but stops after 1/4 turn.
It is not 8x32thd, the nut is loose and it looks like not the correct threads per inch? The 6x32thd nut does not fit at all.

I think it is an Imperial size thread but what size?

Thanks for the help,

Mike McIntyre
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Dec 15, 2019, 06:21 AM
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fiery's Avatar
4 ba.
Dec 15, 2019, 09:04 AM
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Cougar429's Avatar
Quite a few used 1/4-28 or 5/16-24, with the much larger using 3/8-24. All these are fine thread.

I would strongly suspect yours is the 5/16 size.
Dec 15, 2019, 09:23 AM
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1QwkSport2.5r's Avatar
Read here: the other thread that answered the question already.
Dec 15, 2019, 09:52 AM
mcintmg's Avatar
Thread OP

Thread size on a K-Mills .75 diesel?

Thanks so much for your help -- all of you.

The camshaft diameter measured .1417 inches ( using a micrometer) so, ffkiwi is correct then the Mills .75 shaft thread is 4BA (British Association).

Thanks ffkiwi for the info below:

If you want to source the taps-you'll almost certainly have to go to a UK supplier-and you can't do better than Tracy Tools for the range of options on offer:

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