The dealer said that this was not an uncommon problem, but the good news was he had another spine in stock and it would only cost me 20 bucks - much less than I thought it would be. However; the two previous experiences with the screw backing out and the probability of recurrence got me thinking.
In the photo above I have pounded out the shaft and placed it next to the drive. In the center of the picture, just below the large hole in the spine for the shaft, you can see the crack. What's new here are the thru holes I drilled in the spine and the shaft. You can probably guess what's next...
This is what it looks like with the shaft reinserted and a 4-40 UNC stainless steel screw installed. The shaft was surprisingly easy to drill through. I used a 7/64 bit, some oil, and a home edition drill - no drill press required. It only took a few minutes.
The other side looked like this. I shaved off 5 or six threads of the hole in the spine to make it more streamline and attached a stainless steel self locking nut.
I think the thru bolt may be a more robust solution than the factory provided set screw. I had applied thread locker to the set screw, but it still failed, and any attempt at tightening will stress the area. I suspect this issue will get to be very common as drives age.












