'98 Mazak QT-20 turret out of square.

Figured I would start a new thread, since the one about my tailstock and headstock was getting sort of long.

Long story short. Big crash, squared the turret up, though actually all I did was get it back to level with the center of the spindle. Squared up the headstock, and then indicated the face and sides of the turret. .005 over 3 inches on the side and on the face. At least this seems to indicate that the X&Z are still perpendicular to each other.

So today, I look at the crappy schematics and figure there are six bolts that hold the casting to the slides, and I'm guessing that is where I need to be. I don't think I can do anything up by the turret since it appears that the curvic coupling is bolted directly to the casting.

I know some of you guys have some expierience with this,(you've been very helpful in the past) so am I headed in the right direction, hopefully I can get a 'yea' or a 'ney' and a few pointers before I ruin something. I've already got all the covers off and am ready to go.

Thanx.

Bob,

When you get a big crash on a slant bed lathe, a lot of things can go out of alignment at the same time. This is a PITA to rectify, but, all of that shock absorbtion does save potential damage.

When they assemble these things there is a specific sequence; to realign, you need to go in reverse, from the most likely to shift, down to the least likely.

1) The turret side of the curvic coupling is the first to shift usually, and therefore needs to be reset to its original position according to the taper pin locations. Then, do the same for the mating piece on the turret casting. To check, tram along the tool seating surface by moving the x-axis slide in and out (up and down).

2) Next check that the turret casting is square to the ways. Use a good mag base indicator with stiff arms, mount it someplace solid like the ways. Indicate along the face of the turret where the tool blocks mount, by moving the carriage along the Z axis.

3) Check your headstock for parallelism with the ways, by test cutting a hunk of stock, no more than 1:4 ratio of diameter to length. Measure the diameter near the chuck, then near the unsupported end, and compare to detect any taper. Adjust the headstock (big bolts). If the headstock moves on a pivot, or has taper pin holes to realign, you're in business. If not:

4) and the headstock is free to move in any direction on top of the bed casting, the real trouble now is getting it straight, AND in the right position front-to-back at the same time. Put an indicator in the chuck, and sweep tool pot #1 where the X readout normally is 0.000, which hopefully corresponds to spindle centerline. You may find this position specifically referencing an encoder reading somewhere in the inspection report that came with the machine. Now it's a matter of adjusting both front to back position of the headstock on the bed casting until the indicator locates the center of the tool pot, meanwhile making sure it stays straight relative to the bedways. Tedious and time-consuming, but no easy way.

5) If the machine has a tailstock, you can also use either the OD of the quill or its bore to reference spindle center.

Happy indicating.

PS - good time to check machine dynamic level, before starting all of this effort - dont forget, the base casting was levelled before all the components were scraped in and assembled; therefore, machine bed level, as in no-twist, becomes critical.

Thanx for the input, I'm halfway to what you describe. The crash, which I had no part in, was a toolchange at the chuck at 5000rpms. At first I figured it was just the turret, thanx to the help on here, I got through that one easy enough. Center height of the turret is dead nuts to the spindle. Then when I asked about aligning the tailstock I was advised to check the headstock, which was way way way out. I've got that licked, running 7 tenths over 5.2", smaller dia. further away from the chuck. Next I checked the squarness of the turret and now I've got it all apart and started loosening stuff, just by loosening the bolts from the casting to the X slides, I went from .005 over 3 inches to .0035 over 3 inches. Now my problem is, how do I get rid of that last .0035, everything is loose and should move but doesn't. A deadblow didn't move a thing, a 2lb hammer didn't move a thing, I guess I could go with a 10lb, but I really don't want to damage anything. I know the casting is quite heavy, and I'm not quite sure how to move it, bigger hammer?, pop the covers off of the top and lift it with an engine hoist? am I missing some bolts?(I don't think so), prop a rod against the base casting and use the Z?(seems a little abusive). Thats where I am at now, then on to the tailstock.

Do you see any holes (maybe plugged) where there might be a taper pin or two that is used to align the casting to the slide? They should be in front, easy to access.

I'm guessing since you loosened the bolts, the casting dropped down and is now resting on the sides of the bolt holes. Get a crane and a sling fron the back-top side to take some of the weight off. Then jostle it around until one taper pin drops in. Then do the other one, then tighten the bolts.