inconsistent cuts when turning CB 1220 XL

OK Bob was correct, the nut is causing the problem. Specifically the spring-loaded part is moving under load. Many lathes dispense with that and have a simple one piece nut, you have some backlash but you just learn to compensate for it. It's a constant amount that doesn't change.
Try this: re-install the nut in the opposide direction if possible, in other words, if the spring loaded portion was toward you before, install it with that portion away from you and see if the problem is reduced.
Alternately, remove the spring-loaded portion completely
 
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Mark, I will try that. The reason I added springs is because the screws were coming lose and removing the "backlash compensation" in the cross slide. I added the springs (per other designs I saw online) to alleviate the loosening of the screws. I think If i can get the screws to stay put and get the feed nut secured to the carriage I'll be in good shape. Perhaps just simple lock washers on the small screws?
 
The lead screw and nut should be set up so that it is solid in the direction that holds the tool to the work, no springs or adjustments in that direction. The adjustable side of the nut or any springs should be on the reverse side, not taking the heavy cutting loads. It would be better to make a setup that can be adjusted to a solid and robust nut to screw fit. Springs are a weak attempt at a solution.
 
Yes you really should dispense with the springs and shim or trim the nut pieces such that it makes one solid assembly, leaving a tiny amount of backlash- Also what Bob said above; install in the direction where the main body of the nut takes the cutting forces
 
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Go to Smithy and leave Dave a note.
Dave very very knowledgeable about all of the Smithy machines.

Very helpful fellow.
 
I just went thru this recently. First and foremost I should say that I am new to lathes so listen at your own risk. I had the same issue with my Midas 1220LTD. I ordered a new nut which removed most of the lash. IMHO, the small or adjustable end of that nut is the weak point. It only has a few threads and wears more quickly than the larger end. After you have the new nut and lead screw in place adjust the 2 screws until you feel the slightest bit of drag when turning the handle. Reassemble the table and tighten the nut behind the wheel, adjust the gibb screws and oil it. There is a certain amount of lash that remains but it will be much better. You'll notice that the new nut has a smaller gap between the halves than the old nut when adjusted. IIRC, they are <$15. DRO is a big help on my machine. Especially now that I've corrected the the DRO's installation done by the PO, but that is another story. Every day is a learning experience but I'm loving it so far.
 

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I know this thread is old but , recently picked up a 1220 XL. Complete loose mess.
I found the 2 back lash screws just sitting in the valley upon tear down. They where coming loose after reassembly my first thought was to install studs and nylon lock nuts. But for the quick fix I used 222 loctite. Socfar so good . After much trial and error and shims, bearings spacers. I have my cross slide back lash to with in factory spec wich is .008-.014 or so . The cross slide screw, nut , and dial are definitely not “in sync” at least per dial indicator. Im sure those with DRO they could find spots that are off.

My cross side nut threads looked fine but I had to had shims to the small stud that protrudes into the saddle. I have thought of adding a mounting screw to add some rigidity but feel that will just wear the nut faster. Im still cleaning and fixing the lathe but its leaps and bounds better after making sure everything is clean and snug
 
This is how the QCTP is mounted. The kit actually came with a threaded plate that would be mounted under the QCTP, but I found it was too tall for my setup and not allowing me to center my tools.
The threaded plate is so you can fabricate a new mount or dovetail mount style. I opted for a “bushing to take up the slop from the smaller mounting stud and made a Chicago style nut added a bearing washer and all is well on that front.
 

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One thing that I will point out is that any manual machine for consistency requires you to always approach a setting from the same direction. If you get in the habit of doing that, back lash will never affect the finished product. It doesn't matter how much the machine cost or who made it.
 
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