Ok, so the lever to the left of the 1-11 numbered index dial opens a pair of alligator jaw things. This allows the index dial to now spin. What the index dial is is a pinion gear that works on a curved rack on a shifter yoke. When the pinion actuates the rack, the shifter yokes moves left and right to slide a tumbler gear back and forth on the christmas tree of gears. (This is the same thing you do manually on an open qcgb lathe, the yoke is just a big lever sticking out)
The most usual way for the dial to get jammed is that the shifter yoke is not put back right or the dial is not indexed properly. Essentially, the shifter yoke is rides on a rod that runs between the front and back faces of the QCGB. The yoke and its rod and the shifting shoe need to be lined up correctly when reinstalling the outer plate/cover of the QCGB. Another possibility is that the dial needs to be indexed correctly. In other words, the dial goes back and forth between 1-11, but can’t spin all the way around. Like, if you out the outer plate back on with the dial at 11, but the gear at position 1, it would be all messed up.
Another possibility is a bent shaft or damaged gear somewhere, obviously.
I wouldn’t worry too much about opening the QCGB too much. The hardest part is taking the taper pins out of the opening lever and knobs so that you can take the QCGB front plate off. The front plate comes off pretty easily. Only the shifter yoke really stands to fall out. Most everything stays put inside (drain the oil first though!). The shifter yoke is a bit persnickety to get back in with the dial lined up, but you really just have to think about the way the dial turns, and the direction the pinion moves the rack as it goes 1-11 or 11-1. I just can’t remember whether extreme left or extreme right is position 1 or 11 at the moment. Just figure out which is which extreme, put the tumbler and yoke there, dial accordingly, and then put the face plate back on.
I dunno if that makes any sense.
Lodge & Shipley "Powerturn" Lathes
Has a picture of the inside of the QCGB down a ways on the page. You can see the alligator jaws clearly (two rails that have have circle cutouts along them. You can just make out the curved rack in the upper right.
