Removing a turret from a QT20

I bought my first CNC lathe, a 1995 Mazak QT20 which I have been slowly but surely rehabbing. I roughly leveled Z and removed the way twists in X. I've aligned the headstock so that it cuts within 2 tenth taper over 6". A facing cut leaves a small nub at the center, so I figure the turret needs to be clocked. It is square when indicating along the turret outer edge in Z. When I indicate in X I get approx 0.001 along the 3-4 inch holder slot. With a 1" drill rod placed in a new block, I indicate about +/- 0.004 up/down, with the bar being too low. I am trying the reclock the turret and would like some pointers. I loosened the 8 bolts on the face of the turret which I assume attach the turret to the curvic (circled in green on the attached pic). Placed a 1 inch square, 3 foot long bar in a holder and pushed liked hell, but no movement. So I figure that the turret may have taper pins attached. I am now trying to remove the turret by loosening the compression nut on the center shaft and prying the edges and also hitting with a dead blow hammer. The sucker won't budge. This is the first time I've ever tried to do this, so I figured I's ask for advise before breaking anything. I have several questions:

• The rusted ring with several bolts around the center nut I assume is a spline hub and does not be removed. It should come along with the turret, right?
• Do I need to remove the 8 bolts holding the turret to the curvic? I assume not
• Any tricks to unseating the turret? Do I need to build a flywheel puller?
• What is the purpose of the two large set screws on the face of the turret (circled in red on my pic).

Thanks in advance,
Dan

Once the center nut is loose, it should slide right off.

Don't take off the 8 bolts for the curvic.

The 2 "bolts" circled in red. They are actually just covers,
they cover up the holes where the taper pins go. Take them
off and you can see if the pins are in there.

If I remember correctly, that rusted ring in the center with all
the smaller bolts is used to clock the shaft to the turret. If its
always a little high or low when it tries clamping, you can loosen
that and recenter it.

If the turret is stuck on the center shaft, maybe try unclamping the turret,
and then put something between the turret and the casting (in several places,
maybe some of those tapered wooden shims for doors and windows)and let the
machines hydraulics pull the shaft back through the center hub. That should
be enough to break it loose.

Thanks BobW. Using the hydraulics with progressively larger parallels as shims worked. But of course now I have more questions. The curvic on the machine side has 16 detents and the turret side has 8. Does this mean that my machine is capable of 1/2 steps? Tool changes from the controller (t-plus) moves full steps.
Does anyone know if this machine can move in half steps, perhaps with a parameter change?



As suspected, the pins on the turret side are in. The interesting thing is that this turret has been off before (the yellow mark is not from me). Wondering why the pins weren't removed. Any suggestions on the best way to remove these? I'm thinking of punching them out from the front of the turret. I haven't done this before, and I am really starting to love this machine and don't want to f_ck it up!

The pins should come out at the front of the turret. If they came out the coupling side,
you wouldn't have been able to get the coupling off.

The yellow very well could have been from the factory, though I can't imagine a 20+ year old
lathe that had never had the turret off.

As for the pins being in. We've had that argument here many times. It comes from the factory
like that, so some like to put them back in. I personally don't.

As for the 8 and 16, no idea.

Bobw said:

...
As for the pins being in. We've had that argument here many times. It comes from the factory
like that, so some like to put them back in. I personally don't. ...

Click to expand...

Newer Mazak lathes do NOT have the taper pins installed. Makes it a 10 minute job to re-align the turret.