I've recently taken a worn one apart John.
The drive dogs appeared to be half cut through.
Once it was thoroughly cleaned I could see that the drive dogs were pressed in.
I suspect yours has worn away completely.
Unless someone more experienced than me knows better.
Also in my example the felt seal has worn away too. Anyone changed these?
If anyone has a nice way of getting them apart, that might be of interest to our readers.
The main problem is the four small screws have to be undone. I'm sure that after being screwed into the Mazak body, the screws were then snapped or cut off flush. So the bloody things sometimes either snap or pull the thread out. Otherwise they're quite simple to take apart. Ron
They are indeed a sod to remove...I use a rat tailed file to gently file the opposite end to the head flush with the speedo body...A bit of heat doesn't go amiss either before trying to loosen them. The temperatre of boiling water is sufficient...I've drilled and tapped them oversize before after breakages...Ian