A quick update on the Large A&S Universal Machine..
I still have the  gearbox in pieces. I am embarrassed to confess that it turned out it was a self inflicted problem.
I had been facing off some cast iron billets late one night, and the leadscrew ended up covered in messy cast iron swarf. I was cleaning it off, and put the leadscrew in gear to make it easier to get all around it. What I hadn't realised was that the 4 way lever on the gear box wasn't fully engaged, and I'm guessing that it dropped down to some intermediate position, which meant I was trying to run the gearbox at two different speeds, and the gearbox didn't like it!  It's particularly galling, because if I had been doing a screwcutting job, I would have double, nay, triple checked my gear settings. When I realised what had happenned, I didn't stop swearing for about a week.
Anyway, the end result was that the gear change shaft inside the constant mesh gears jammed. I have taken it all apart, (not easy on a machine that I don't think has been apart since it was assembled back in the 1960's ) and I have sorted the gear change shaft problem (which was an almost invisible ridge near the keyway slot, caused when the drive dog slammed into the keyway) and the change shaft now operates smoothly as before.



However, there is still some other fault, as I'm not getting any drive from the main shaft into the 12 speed box. I think I may have a broken drive pin somewhere.... 
(I have to say, having spent so much time renovating this machine, I got a bit p****d off at this point and just left it for a few months. I also got side-tracked by alternative projects, such as a part built 7 1/4" gauge 0-4-2 steam loco, and a Bridgeport milling machine.)

I will get there in the end, but I'm really wishing I hadn't bothered to clean up the machine that night!

Update: The large A&S Combination machine is back up and running again.

Problem was a 1" dia. sheared shaft..


I had to make up a stub shaft replacement


Everything is all back together again, and no bits left over, which is always a plus with a gearbox repair.
Have also made a mental note to myself NOT to use industrial machinery late at night when I'm too tired and my brain is switched off...

Anyway, just used the A&S mill to repair some rack teeth on a Bridgeport Ram casting, so the shaft repair looks to be solid enough.

Dave