Gearbox Sprocket Lockwasher Screw

Onder said:
As for Virginian draconian driving penalties, it is a very good reason simply to not live there. If you work in DC not hard to live elsewhere nearby. Use your feet in self defense.
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Right, killing people is sport in DC! Normally done with a gun though.
robs ss said:
...and the title of this thread is Gearbox Sprocket Lock Washer Screw - WTF?šŸ¤£:rolleyes:
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Ya, the thread was (should have been) over at post #2 then came post #3 and its new life began. Hopefully it will die soon! :D
 
Not ready to let it die. Back to the original topic....
I emailed AN with an excellent suggestion. When they make another batch of GB sprockets tap them for an American thread. And furthermore...PROVIDE each sprocket with an ALLEN SOCKET SCREW. This would cost peanuts and would make for happier customers.
Usually the existing slotted screw is well beaten up trying to get it out and people forget to order one. AN told me no dice.
 
seattle##gs said:
Not ready to let it die. Back to the original topic....
I emailed AN with an excellent suggestion. When they make another batch of GB sprockets tap them for an American thread. And furthermore...PROVIDE each sprocket with an ALLEN SOCKET SCREW. This would cost peanuts and would make for happier customers.
Usually the existing slotted screw is well beaten up trying to get it out and people forget to order one. AN told me no dice.
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This! Every gearbox we do we encounter this screw completely chewed up. It's made from the softest metal in the western world.

I know it won't happen because it's not original, but I wish Andover would take it a step futher and drill 5 holes thereby allowing the socket screw head to abut on one of the flats of the retaining nut and hold it in place, ala TTI boxes, and do away with that washer altogether.
 
I must be missing something. An 8-32 is a common screw in the UNC thread series. In other words, it is an American thread.
If you want Andover Norton to deviate from their blueprint specifications to increase the convenience to the end user, lobby them to use a metric thread.
The only countries that use the imperial system as their official system of measurement are the U.S., Liberia and Myanmar.
 
Stephen Hill said:
I must be missing something. An 8-32 is a common screw in the UNC thread series.
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You are confused. Previous poster said they found an odd (not Andover) sprocket and the only fastener that they could find to fit was an 8-32. If Iā€™m not confused the standard Commando sprocket thread is 2BA. Everyone loses (except for the concours restorers).
 
Holmeslice, I agree, I was confused.
When Greg said a 2BA tap wouldn't start, then later took an 8-32 screw, I assumed the screw called for was an 8-32.
According to the AN website, it should be a 2BA.
andover-norton.co.uk

Andover Norton - SCREW 2BA x 3/8

SCREW 2BA x 3/8
andover-norton.co.uk

An 8-32 has a major diameter of .164", versus a 2 BA of .185". Obviously not an ideal substitute.

Speaking of confusing, try explaining this:
"British Association threads were a metric thread system devised for small screws. Not metric like you might expect, but with diameters determined by a factor proportional to a power of the logarithm to the base 10 of the thread pitch in millimetres."

BA & ME Threads

Engineers data tables for BA and ME threads
journeymans-workshop.uk journeymans-workshop.uk
 
I started this thread about a non-standard sprocket. The correct screw is 2BA x 3/8" but the sprocket I was talking about was from a parts buyout, so I have no idea where it came from, and it went to the recycle bin.

The weird part to me is that the "cycle parts" on a Commando are mostly UNF with a few UNC. The only other BA threads I can think of are in the Amal carbs and for the gearbox inspection cover. For the inspection cover it makes sense since all threads in the gearbox are British. The engine is a mismatch of British threads including BSC/CEI, BSF, and BSW and then UNC/UNF for the crankcases.
 
A 2BA screw is .185" diameter x 31.4 tpi. I've been meaning to ask if anyone knows if there's some reason for the fractional TPI of the BA standards??? I understand why metric simply counts the distance between threads, so isn't a thread pitch that relates to the number of threads per unit of distance (such as an inch in TPI) Is there some guiding mathematical logic to the "BA" measurements????
 
L.A.B. said:
And they are the same 2BA x 3/8" 00.0450 screws as the sprocket plate screw.
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Yes, and thinking about it, British thread for the sprocket is logical since it can be considered a part of the gearbox which is all British threads.
 
These are out of stock right now but are normally available: https://britishfasteners.com/2ba-x-3-8-shcs-s-s-1012.html

These are in stock but only 5/16" long and I haven't tried them: https://britishfasteners.com/2ba-x-5-16-shcs-s-s-1011.html

Since they are stainless steel, they must be installed with anti-seize or medium thread locker - I recommend the thread locker.

They are much easier to install and removed. For those with socket head cap screws for the outer gearbox cover these are a nice match for the gearbox inspection cover.
 
o0norton0o said:
A 2BA screw is .185" diameter x 31.4 tpi. I've been meaning to ask if anyone knows if there's some reason for the fractional TPI of the BA standards???
Click to expand...
They are unusual in that they were probably the most "scientific" design of screw, starting with 0BA at 6.0 mm diameter and 1.0 mm pitch and progressing in a geometric sequence where each larger number was 0.9 times the pitch of the last size. They then rounded to 2 significant figures in metric and then converting to inches and rounding to the thousandth of an inch. This anticipated worldwide metrication by about a century. The design was first proposed by the British Association in 1884 with a thread angle and depth based on the Swiss Thury thread,

British Association screw threads - Wikipedia

en.wikipedia.org en.wikipedia.org
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So clear as mud.
 
I think BA is also used in points cover and in Smiths speedo & tach.
marshg246 said:
I started this thread about a non-standard sprocket. The correct screw is 2BA x 3/8" but the sprocket I was talking about was from a parts buyout, so I have no idea where it came from, and it went to the recycle bin.

The weird part to me is that the "cycle parts" on a Commando are mostly UNF with a few UNC. The only other BA threads I can think of are in the Amal carbs and for the gearbox inspection cover. For the inspection cover it makes sense since all threads in the gearbox are British. The engine is a mismatch of British threads including BSC/CEI, BSF, and BSW and then UNC/UNF for the crankcases.
Click to expand...
 

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