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Misc: Everything Else 5 inch speedo studs

Black Flash

Well Known and Active Website User
VOC Member
Hi there,
I am finishing my black shadow rebuilt. Now is the time to fit the 5 inch speedo. In KTB it is mentioned that the speedo has 3 studs screwed into the casting which take 0BA nuts.
Now my speedo has no studs fitted and I have no clue what thread is used in the casting.
Can anybody throw some light on this topic?

Thank you very much for your help in advance.
Bernd
 

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
In my KTB which is a 4th edition it says on pg235 that the 3" Speedometer has two studs on the back which are 6mm. It also mentions 0BA but that info is wrong and they are 100% M6 as the instrument was a Metric instrument and all the threads in that instrument are metric, but this is not the speedo the question was about.

Now the question was about the 5" Shadow Speedo which is different. The case for the 5" speedo was specific to Vincent and in KTB pg 238 (4th edition) it says the speedo is held onto its bracket with 3 off 1/4" BSW setscrews (bolts) 5/8" long. (not UNC which is an American thread and not used in UK in the 1950's).

I just dug out a spare 5" speedo and checked the setscrews and they are 1/4"BSW.

Simon
 

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Black Flash

Well Known and Active Website User
VOC Member
Hello Bruce,
Living in the metric hemisphere, M6 was the first I tried but it didn't work, enters one turn and seizes. The thread looks more coarse. I tried 1/4 unc as these are the Allen bolts you get today as a replacement for bsw, but they won't enter at all.
I will grind my thread gage a bit thinner to see if I can enter it into the blind hole.
From the looks I would say it is not as coarse as bsw, but I will check again.

BTW my KTB is second edition, so no thread mentioned

Thank you all very much for your help
Bernd
 

mercurycrest

Well Known and Active Website User
VOC Member
Hello Bruce,
Living in the metric hemisphere, M6 was the first I tried but it didn't work, enters one turn and seizes. The thread looks more coarse. I tried 1/4 unc as these are the Allen bolts you get today as a replacement for bsw, but they won't enter at all.
I will grind my thread gage a bit thinner to see if I can enter it into the blind hole.
From the looks I would say it is not as coarse as bsw, but I will check again.

BTW my KTB is second edition, so no thread mentioned

Thank you all very much for your help
Bernd
The thread pitch is a few degrees off 55deg vs 60 deg. Chase the holes with a 1/4-20 UNC bottom tap and they'll work just fine.
 

Black Flash

Well Known and Active Website User
VOC Member
Just back from the workshop.
You were right, I carefully tried cleaning up the threads with a 1/4 BSW tap and it worked fine.
Now after brexit the problem is having to order the srews from England.
Usually the packet arrives near my area within 2 days, but then it takes16 days [last time I ordered from the spares Co] to clear the customs.
Seems the EU found a new way to punish the Brits for leaving the EUSSR.
 

erik

Well Known and Active Website User
VOC Member
Hallo Bernd! Ich schau mal ob ich noch was passendes finde. Erik
Hello Bernd! I'll see if I can still find something suitable. Erik
 
Last edited by a moderator:

Old Bill

Well Known and Active Website User
VOC Member
Refurbished a few of these speedo heads over the years, the threads in the alloy are often defective and require a thread insert in which case l shorten the set screws to half an inch and apply a low strength thread sealant as vibration has a habit of working said screws loose and there is nothing worse than a loose screw, hey ho.....
 

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