Need help trueing my Dalton six lathe

[Jbullfrog]

I have a Dalton "six" metal lathe that I purchased on a mentor's estate sale. I'm having issues because the chuck isn't spinning true. If I remove the chuck and check the spindle it's great, so i'm guessing it's the mating surface of the chuck or the threads that are cocking it. Any ideas how to correct this .005 runout?

 

[rockwithjason]

does the chuck have a mounting plate? if it does, take the chuck off of the mounting plate and check the plate for true.

 

[thaxboyd]

Sometimes the locating surfaces get little dings in them from mishandling that creates high spots and need to be stoned... Seen this a lot through the years

 

[WhoWhatNow]

I'm a complete novice at machining but how are you measuring your runtout? I believe it should be with something like a piece of drill rod chucked in the lathe.

 

[thaxboyd]

I'm a complete novice at machining but how are you measuring your runtout? I believe it should be with something like a piece of drill rod chucked in the lathe.

Yes... and a dial indicator

 

[A_Pmech]

If the chuck face is running out, take a skim cut on the chuck backing plate.

If the chuck jaws are running out, disassemble and clean the chuck and try again using something like a wrist pin held in the chuck jaws. If it's still a problem, relieve the shoulder on the chuck backing plate and knock the chuck true with a mallet before tightening the mounting bolts.

 

[spongerich]

.005 isn't that far out for a 3 jaw chuck, especially an older one. Even good 3 jaw chucks will run .002-003 out. If you want closer tolerances than that, find a 4 jaw. They're a PITA to setup, but once you get good, you can get parts running true to .0001 in a minute or less. Another option is a Buck (or buck style) 3 jaw Adjust-Tru type chuck.

You should also check it at several diameters since runout can vary quite a bit. If the chuck was used most of the time with 1" stock, you'll probably find more wear and more runout there than you will if you chuck a 2" bar.

Disassembling and cleaning it is definitely a good idea.

In theory, whenever you mate a chuck to a machine, you should remove it from the backplate and take a skim cut on the backplate to ensure concentricity with the spindle.
Make sure that the spindle threads and chuck are immaculately clean, then clean them again. Run your finger across all the surfaces to feel for any debris or dings. Small dings can be stoned down. Also make sure that the backplate threads all the way on and that the register is mating right. The register aligns the chuck, NOT the threads.

 

[larry_g]

Since you have another lathe in the picture, can we assume that you are somewhat experienced? First thing to confirm is is the test piece your using round? I've seen a few led astray by assuming their standard is round and straight. Are the jaws on the chuck straight or are they a bit bellmouthed? Are the jaws a good slip fit in the body or a bit loose from years of use? As others have said above start with the backing plate and confirm it is good and true, and then mount the chuck. Confirm that the runout is present consistently with a few different diameters of standards. If not consistent with different diameters then it is not a mount problem but a chuck problem. Mark the high spot on the chuck and then loosen the test bar and rotate it 90* and check it again, rotate once more 90* and check a third time. Check and recheck each and every piece in the stack until your confirm exactly where the problem lies.

That said and as others have said .005 is not unreal for such an old machine and what looks like not the greatest backing plate.

lg
no neat sig line

 

[3 Gun Shooter]

You might want to get a chuck with removable jaws. Make some aluminum jaws and bore them in. You can make the jaws fit what ever part you are holding.