DMTG CKE Adjustment
OK - here's the update.
I am now able to turn an unsupported 1.4" diameter 6061 test part over a 4" length with no measureable difference in diameter using a "tenths" micrometer. Prior to adjustment, the error was on the order of 0.001"/1" of turned length. Needless to say, I'm quite pleased with the result!
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Here's a write up of what I did - hopefully, it will help others.
To adjust the CKE headstock so it turns true:
1. Remove the outboard (z-) end cover from the lathe.
2. Remove four bolts from the z-axis ball screw cover (you will have to move the carriage to find all the bolts).
3. Move the carriage as near the spindle as possible.
4. Remove the ball screw cover.
5. Remove the spindle cover safety switch assembly.
6. Remove the spindle cover and mount ring (this may require removing the chuck).
7. Remove the small sheet metal cover below the z-axis ball screw.
8. Remove the large sheet metal cover which surrounds the spindle.
9. (replace chuck if required and) Turn a length of about 4" on a test piece approximately 1.5-2" in diameter and measure at the inboard and outboard ends, recording the difference. Leave the stock in the chuck.
10. Mount a dial indicator in the turret and move the carriage and cross slide to zero the indicator near the outer end of the test piece.
11. Loosen the socket head bolts (12mm Allen wrench) at the z+ end of the headstock base. This may require a "cheater pipe" as they may be quite tight.
12. Loosen the bolts at the z- end of the headstock. One takes a 12mm Allen and one is 10mm Allen. They may also require lots of force.
13. Use a 6mm Allen wrench in the set screws in the adjusting block between the z- end mount screws to drive the headstock in the x+/x- direction required. Note changes in the dial indicator to find a starting point for adjustment.
14. Retighten all four headstock base mount screws.
15. Take another light cut on the test piece and measure the result.
16. Iterate adjusting and testing as required.
17. Final tighten the four mounting screws and replace all covers.
Notes:
1. I started with a 12mm "L" shaped Allen wrench that was about 8.5" long. That was too long to fit in the outboard end of the headstock and, also, the z-, x- bolt is too close to the base casting to use a conventional "L" wrench very well. I cut 1.75" of the long end of the wrench off. I used the remaining long piece conventionally and used the short cutoff in a 12mm socket on a 3/8" ratchet. That worked well on the z-, x- bolt.
2. On my machine, it seems like the (notional?) pin around which the headstock should rotate on the z+ end is missing or loose. I ended up leaving the z+, x- headstock base screw partially tightened during adjustment in order to use it as a pivot point.
3. I either jammed the adjuster on the z-, x- end or ran out of travel near the end of my sequence of adjustments. I used a large screwdriver in the slot by the adjuster to wedge the headstock over for the final adjustment.
4. In my case, it took 5 iterations to zero the machine.