Thread sizes

Chassis, frame, instruments, fenders etc.
Forum rules
Please do not start new topics here, but here: New Panhead and Flathead topics
Post Reply
Pan57Johan
Posts: 38
Joined: Wed Nov 18, 2009 10:06 pm
Bikes: 1957 Bobber
1950 BSA Bobber
Location: Sweden

Thread sizes

#1

Post by Pan57Johan » Sun Mar 07, 2010 8:06 am

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



Bosheff
Posts: 1234
Joined: Fri Jul 03, 2009 8:23 pm
Bikes: 65 FLH 82 FLH
Location: Michigan
Been thanked: 41 times

Re: Thread sizes

#2

Post by Bosheff » Sun Mar 07, 2010 3:16 pm

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

Panacea
Posts: 1864
Joined: Fri May 24, 2002 1:00 am
Bikes: 64FL 99FLHR 01FXSTD
Location: Mpls. MN.
Has thanked: 14 times
Been thanked: 57 times

Re: Thread sizes

#3

Post by Panacea » Sun Mar 07, 2010 4:14 pm

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

NightShift
Posts: 532
Joined: Tue Apr 21, 2009 4:20 pm
Bikes: Two Schwinns, a Hercules, and a Hiawatha
Location: Underground in Illinois
Has thanked: 1 time

Re: Thread sizes

#4

Post by NightShift » Sun Mar 07, 2010 8:57 pm

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,

Bosheff
Posts: 1234
Joined: Fri Jul 03, 2009 8:23 pm
Bikes: 65 FLH 82 FLH
Location: Michigan
Been thanked: 41 times

Re: Thread sizes

#5

Post by Bosheff » Sun Mar 07, 2010 11:11 pm

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

Post Reply

Return to “Chassis, Frame & Instruments”