Need info on thread pitches used on my 1937 R12

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niklnikl
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Need info on thread pitches used on my 1937 R12

Postby niklnikl » Sat Feb 03, 2018 5:04 am

Hi All.
I recently purchased this R12 and need some education on the odd thread sizes used on the bike.
For instance, some of the engine and gearbox covers appear to use nuts that are 6mm in diameter, but the thread pitch
is some old obsolete size. I see 6mm x 0.85 specialty taps being sold. Is that what I'm finding on my bike?
I don't have a 0.85 thread pitch gauge lol.
Funny thing, I found that SAE 1/4"-28 nuts appear to be very close to that odd pitch size.
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Bill Smithson
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Re: Need info on thread pitches used on my 1937 R12

Postby Bill Smithson » Sat Feb 03, 2018 8:23 am

Hi,
Before you try a wrong thread on the bike go to the fount of all knowledge for old BMW's, register and ask your question.
I've found both the single and boxer forums invaluable over the years.
There is an English speaking version or you can translate with Google.

http://www.bmw-einzylinder.de

niklnikl
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Re: Need info on thread pitches used on my 1937 R12

Postby niklnikl » Sat Feb 03, 2018 8:29 am

Thanks Bill!

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george baker
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Re: Need info on thread pitches used on my 1937 R12

Postby george baker » Mon Feb 19, 2018 11:18 pm

hi
nice looking bike, can you buy metric thread gauges in the us

how about Pressing the bolt into something soft, like wax, and measuring for 10 threads

george
Member 21, R100R, K75 and a Hyosung 250 FOR SALE

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Ruralman
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Re: Need info on thread pitches used on my 1937 R12

Postby Ruralman » Tue Feb 20, 2018 1:53 pm

Nice looking bike!
Regards
Keith


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keiththeoutfitter1
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Re: Need info on thread pitches used on my 1937 R12

Postby keiththeoutfitter1 » Tue Feb 20, 2018 2:08 pm

If I'm not mistaken, .85mm pitch equates to 29.9 threads per inch so if you say that 1/4" x 28 appears close then you most probably have the .85mm thread pitch.
Keith
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