wmh9680

Good evening everyone, well it's snowing again in Chicago, after 12" a couple of days ago. Hope your weather is better. Does anyone know what the thread size and pitch on the adjusting chain on the shifter indicator on a SA AW hub. on the chain end where it connects to the shift cable. I think one of mine need cleaning up. Thanks, Mike

Velo Mule

The side where the cable attaches to the indicator chain I believe is #5-40. So, 40 threads per inch. This should be confirmed. My quick method for checking would be to get a #4-40 screw which is much more common and see if the threads of the #4-40 mesh with the threads from the S-A indicator threads. Then check the diameter. If the indicator chain is a #5 then it will be a little bigger diameter than the #4 screw.

Let us know how this goes.

homelessjoe

A thread gauge is only a couple of dollars and is a must have if your gonna work on British bikes.........its like a set of feeler gauges except every blade has teeth cut into them to measure threads

wmh9680

Thanks, I have one of these in metric and SAE but it does not go small enuf. When I retired I went thru all the nuts and bolts I have collected over the years and organized them. I thought I had what you are talking about, I'll have to look around. Thanks again, Mike

wmh9680

Thanks, I will try this and let you know, Thanks again, Mike

CV-6 

That is an ingenious way to determine threading. Nicely done.

homelessjoe

I think you will find old bicycle threads are a whole new world especially on older English bikes......they used BSW......British Standard Whitworth 55 degree thread angle.......12 tpi....instead of 13......rounded crests..........the hex heads are neither standard nor metric

wmh9680

And I suppose taps and dies are very hard to find and very expensive. Thanks, Mike

Velo Mule

This does look like a #5-40 screw thread wmh9680 . I was able to verify the thread pitch using a #4-40 screw. The thread meshed correctly, so the thread pitch is confirmed. I checked the major diameter with a caliper and came up with .120" which is correct for a #5-40 screw.

The picture below is a #4-40 screw meshing with the indicator chain thread. You may notice that the diameter of the Sturmey Archer part is slightly bigger than the #4-40 screw.



You probably won't find a #5-40 nut at your local hardware store. They are available from industrial supply sources. McMaster Carr has them in steel, brass, stainless steel and aluminum.

wmh9680

Thanks, I have a 4-40 tap and die and it will screw in (loose fit but it does grab the threads). I also have an m3 and it will not, threads are to tight/small. I haven been able to locate a 5-40 yet. Thanks again, Mike

Velo Mule

wmh9680 you will have to go to places that are for machinists and mechanics.

MSC Industrial #5-40 tap

Travers Tool Supply #5-40 tap

McMaster Carr standard tap page

For McMaster Carr use the filters on the right side of the page and check #5-40 for the tap size.

Standard taps have a taper that helps to cut the threads gradually. To clean up the threads to the bottom of a hole would require a plug tap or bottoming tap. A plug tap has a slight taper and a bottoming tap will cut threads right down to the bottom of the hole. If it were me, I'd get the plug tap to clean up threads in the adjuster barrel.

wmh9680

Thanks, I will be investigating. Mike

wmh9680

Well, A 5-40 screw does fit in easily (maybe a tad loose) but the 5-40 nut does not want to thread on. Mike