[eartaker]

I chucked up a price of bar stock and centered it with a live center. I made 1 pass on the bar and it came out .010" larger near the chuck than the live center. Anyone else have this problem?

Maybe I need a proper way to align my tailstock.

[blades]

I've seen a couple different threads on this, and they usually evolve into a fairly lengthy discussion of other potential causes and various fixes. But yeah, it sounds like you probably have tailstock issues. Have you tried chucking up a test indicator and swinging it around the nose of the tailstock to see what it looks like?
In the simplest terms, it could merely be out of alignment. But there are other factors that could complicate things, such as the tailstock sitting at a slight angle, or perhaps the tailstock quill is traveling in & out at an angle, or even the headstock not sitting parallel to the ways.

[eartaker]

Sounds like a can of worms.... I hope it is just out of alignment. I will throw a few indicators on it and see whats going on.

[cutsall]

Most lathes have an adjustable tailstock consisting of of two allen head socket screws one on the side facing you and one behind. If your tailstock is not made this way you have no choice but to check the headstock. Turn a bar without the tailstock if you get the same results your headstock needs alignment if not it is your tailstock. Good luck.

[chronic]

Also if this is a brand new issue, you might simply have chips underneath your tail stock.
Its pretty easy to get crap under them on these small lathes that dont have wipers on the tail.

[knudsen]

I'd start with Rolli's Dad's Method first.

[eartaker]

Well I just cut a peice of aluminum without the tailstock and I have the same problem. It is off by aprox .002" per 2". will have to look into how to align the headstock.

[photomankc]

Might want to start by leveling the lathe first and then start working on the alignment issues afterwords. Assuming that you are like me and have procrastinated on leveling still.

[eartaker]

The lathe is pretty much level. I looked at Rollie dad's method but not sure how that helps me in aligning the headstock. Seems like it will just tell you how far it is off. I will have to look more into it. This is a new issue, I had an incident a while back when I was cutting and one of the chuck jaws slammed into my cross slide and stopped the chuck. I had a large piece in the chuck and the jaws were protruding out of the chuck. I'm guessing this moved the headstock.

[jetwelder2007]

how is the chuck held onto the spindle, if it's held on by cam locks. These cam pins and locks could be bent. If that's not the case then your headstock is for sure out of alignment. Depending on the type of machine the headstock will be held down by 4 bolts. You will need to remove the belts andand unbolt the headstock. Place an indicator on the carriage and place a ground peice of stock in a collect holder in the spindle. Run the indicator down the length and adjust the headstock as you need. Set the zero point close to the headstock and move out toward the tailstock. This should work for you ok.

[eartaker]

It is a Lathemaster 9X30. The chuck is held to the spindle with 3 bolts.

[Dano523]

Your going to need to attack the problem from both ends.

With the chuck cleaned, start off with a piece of perfectly straight stock in the chuck (4" protruding out the chuck should be fine), then reinstall the the chuck in the spindle so there is not run out on the piece of stock (read gauge off the stock and not the outside of the chuck when you are resetting the chuck.

Now attach the indicator on the compound rest, and check both the side of the piece of stationary stock length wise, and the top of the piece of stock as well (read turn the chuck by hand to a new rotation setting a few times to make sure that you are getting the same readings to confirm that the piece of stock it straight).

Now if you are clean both way down the stock, the chuck head/spindle to the bed are fine. If not, then you need to loosen the spindle head to the bed and shim/ reset it so the chuck through bore is running true to the bed.

Once doe there, drop the piece of stock back into the chuck with about 1" exposed, retighen the chuck, indicate the piece of stock again to make sure it's running true when rotating, set the compound rest up around 20*, and take the tip of the stock piece to a sharp point.
Note, for this, I have a old end mill that I have precise ground to a point for check testing against the tail stock.

Drop in a dead end center in the tail stock with the tail stock set at 0 distance out, bring the two tips together with a razor blade between them to see if the two tips are coming together correctly, and if not, reset the tail stock via shims if needed. Now take the tail stock out to about 1/2" short of max throw, and bring the tips back together with the razor blade between them again to confirm that the tail stock throw is running true with the center line of the chuck. If not, then you will need to shim and adjust the tail stock so you have it running true to the bed the same as the chuck/head.

Once you have all of this adjusted and running true so far, drop in a piece of rod to run a few passes on using a clean live center, and make passes with the tail stock set 1/4, 1/2, 3/4. and full distance of what the bed has to offer, all the while checking each pass to confirm that turned piece is being turned true/same all the way a crossed. As for why the different lengths of the passes on the bed, if the bed is twisted, out of level, or not true, this could be causing the problem and the bed problem will need to be resolved.

P.S. make sure that the bed is clean, and the jibs tight as well.

[blades]

Maybe start by removing the chuck use an indicator to see if your chuck faceplate runout is still good (ruling out a potentially damaged spindle).

If the faceplate runout looks ok, then check the runout measurement of the chuck by chucking up a piece of round stock (preferably something like a dowel pin that's nice and round & straight to begin with).

If the runout isn't terribly excessive, then it looks like headstock alignment issues.

This method should (in theory) take potentially suspect components out of the picture one by one.

EDIT: Dano got his post in before me... his method will look at the entire lathe, while my method is a shortcut that only looks at the chuck/headstock.

[knudsen]

It is a Lathemaster 9X30. The chuck is held to the spindle with 3 bolts.

If you didn't put that chuck on yourself, I would be suspicious of some crud behind it. You might just pull the chuck off and clean it and the plate.

[Dano523]

If you didn't put that chuck on yourself, I would be suspicious of some crud behind it. You might just pull the chuck off and clean it and the plate.

If that is the case, then it's time to pull the spindle as well to clean the bearing/seats and re-grease them as well. You will be surprised on all the debris that you will find in the grease just trying to take out the bearing and seats well before there normal life span.

[eartaker]

I did the chuck since i switch from a 3-jaw to a 4-jaw every now and then. The faceplate is fine and I even faced it off when i first got it.

[knudsen]

Re-reading the thread, you should get a test bar on it and see if it wobbles. If the head is just misaligned, it should still spin true and not show much on an indicator.

I had a large piece in the chuck and the jaws were protruding out of the chuck. I'm guessing this moved the headstock.

If the test bar wobbles, get that chuck off and indicate the spindle. From the crash, you could have a bad chuck, bent spindle (gulp), bent flange at the end of the spindle, or misaligned head, but that won't flunk the test bar check. Could also be the chuck is no longer flat against the back plate. Not on a lathe, but I've seen more than one mechanical assembly take a wack and stretch a bolt. First guess, bent jaw.

You could just try your other chuck, if you didn't already.

[eartaker]

Hmm I hope it isn't something to big.

[eartaker]

not a bent spindle... there is no wobbling of spindle.

[knudsen]

That's good news. Does a test bar wobble? If it does, It's got to be the chuck, the back plate or the union between the back plate and spindle.