Thread sizes

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Pan57Johan
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Thread sizes

#1

Post by Pan57Johan »

What is the thread size on a big twin springer 1" neck stem?

And another strange thing. The four transmission bolts are supposed to be 3/8 UNF, rigth?
But 3/8 UNF nuts fit, but not perfect. And on one of them it doesent fit at all, and it aint 5/16 either...
What size can that one be?

Thanks,

Johan
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Re: Thread sizes

#2

Post by Bosheff »

Can't help ya on the thread count on the springer. If it's a Big Twin it is 1" O.D. A 45 is 7/8" O.D. As for yer tranny studs, they should be 3/8 fine where they come out of the case. Sounds to me like somebody replaced them with metric or whatever they had available. The 5th mount bolt is 3/8 course....bosheff
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Re: Thread sizes

#3

Post by Panacea »

Johan, It's possible one of the tranny bolts has been replaced with an oversize to repair a stripped out thread. Mike
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Re: Thread sizes

#4

Post by NightShift »

Dear Johan,
All big twin springer stems after 1936 are 1"-24tpi. And tranny base studs are all 3/8"24tpi where the nut goes but they are coarse in the aluminium. The oversized studs are 1/2"-13 in the aluminium.

Hope this helps,
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Re: Thread sizes

#5

Post by Bosheff »

Oversize studs are oversize on the end that threads into the trans case. The end that sticks through the tranny mounting plate is 3/8 fine regardless of whether it is original stock specs or is an oversize piece....bosheff
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