[nlh]

Hi folks,

Looking for any information I can on the proper procedure to realign the headstock on an early 80's (~'83) LB-15 lathe. Machine has cut a taper ever since I got it. Found the turret out of whack among other things. Was able to get the turret back into line somewhat but still not great. The out of line condition is such that the further out from the head stock, the larger the diameter.

Also have problems trying to hold tight tolerances on 2 different diameters. For instance, with tweaking to offsets I can hold a 1.5" diameter to a tolerance of (~+-.0005" or less), but a 2" diameter will be off by several thousandths. End up setting my parts high with the offsets, and then tweaking the program and offsets several times to bring the diameters and taper into spec.

As far as taper, without the tailstock, about .002" -.003" in 5in. Slightly less when using the tailstock.
Right now I have no work and just need to take time to do maintenance. Should have plenty of time on my hands for the forseeable future.

Thanks

[Goldorak]

for the taper , check the spindle alignment with the bed

and for holding tolerance, check the x vise for backlash or check the guide ways for wear or lack of lubrification

[CarsonD]

On the LB10 there are four (5?) bolts holding the headstock in place that need to be loosened.

Below the spindle is a cover plate that allows you to get to two bolts and a eccentric bolt.

Two are under the cover over the spindle.

After they are loosened the headstock will pivot on a pin in the rear of the headstock when you turn the eccentric shaft or bolt in the front. I think an Allen wrench fit in it. It is right in the middle between the two bolts that where under the cover plate. I remember it took me a while to find it.

I chucked up a piece of 2" aluminum and skimmed it. I would check it by measuring and running an tenths indicator along it until I got it turning true. I was lucky that running it along the top showed I had little error. All you can really adjust for with the pivot pin is getting it true along the side.

It took a lot of tightening and and adjusting and re-tightening but it was well worth it having it lined up again.

I imagine your LB15 is similar.

[CarsonD]

Hi folks,

Snip...

Also have problems trying to hold tight tolerances on 2 different diameters. For instance, with tweaking to offsets I can hold a 1.5" diameter to a tolerance of (~+-.0005" or less), but a 2" diameter will be off by several thousandths. End up setting my parts high with the offsets, and then tweaking the program and offsets several times to bring the diameters and taper into spec.

Snip...

Thanks

Usually the problem with not being able to get different diameters to come out as programed is because of tool centering.

A tool is centered correctly when you face the bar off and have no cut off tip. What I do is start a little low and face and see if I have a little tit. Then I shim up until it just disappears. Then your different diameters should also come out pretty close.

Once you done it and know your center height is good you can take out the tool and all of the shims and measure the whole stack with a drop indicator. Then next time you put a tool back in that holder you have an idea on how many shims you need.

The Okuma's I've run before had the tool holder center height about .01 low.

[nlh]

CarsonD,

Thank you very much for that information! As I should have guessed, I have yet to have a chance to adjust this machine. Seems every time I start doing maintenance I get just enough customer work to take me away. Thus far I have managed to get my Mazak pretty much taken care of, but have not had any time for the Okuma.

Just a question though concerning your method of checking alignment with a tenth indicator. By taking a skimming cut along of the length of the 2" bar, and then running an indicator along the cut length, the indicator should read 0 even if the headstock is out becuase the cut should be perfectly parrallel with the Z axis ways..., correct? Am I over thinking this, maybe I read your post wrong? Wouldn't measuring diameters at the start of the cut vs. the end of cut be a better way to check alignment? Just trying to clarify.

Thanks again.

[Superman]

Tool not on centre height,
Can be caused by a couple of hard knocks on the tool turret and the curvic couplings may need re-adjusting or taper pins replaced ( some operators leave then out to allow less damage if a bang happens )

Check the maintainence and parts book for method of re-aligning

[CarsonD]

Your right about that.

I do remember using a tenth indicator but maybe that was after I got all of the taper out checking with a micrometer. I must have used my dial indicator mike because I remember getting it true for the eight inches or so I turned.

I think it was after that I ran my dial indicator along the top and was glad to see that it didn't really change much. That would have meant cleaning out the dirt under the headstock itself or shimming one end.

I remember now being glad also that it turned a straight line indicating the ways for the turret ran in a straight line and not veer off like you might see if the ways were worn.

It was well worth all of the trouble for me. It was one an old machine that I ran when it was younger. I left for about twelve years and when I returned it had, had the headstock rebuilt and I don't think it ever got realigned right.

Anyway it saved a lot of trouble trying to program for the taper. You probably already know you can't just program out all of the problems an out of aligned head can create.

[CarsonD]

I remembered something else on the headstock alignment today.

When I loosened the bolts to adjust eccentric pin I had an indicator on the side of the material some way so I could see how much it was moving. Also how much it was moving while the bolts were tightened so I could allow for that.

It was only for a estimate though. I think I started with about .001 per inch of taper. Since the place the headstock is pivoting is so far back I could only guess each time I tweaked the eccentric pin how much to go. I think I move it about .025 total but that is just a guess.

Every time you get closer it gets easier to guess.

[nlh]

Thanks again Carson.

I have some basic instruction in one of my manuals, but it's unclear at best. Probably to force the owner into getting a factory tech in to do the job.

I'm hoping the LB-15 has the same eccentric pin that is on the LB-10. It will sure make the job easier.

[OkumaWiz]

Wasn't going to say anything, but had to chip in...

Before doing all of this is is a good idea to make sure your machine is precision leveled. More importantly that there is no twist or bow in it. This can affect your center height and straightness readings. Check left right top bottom in both directions with your level sitting on the top of the turret. Once you are sure it's straight with now bow or twist, I then normally check the slot in the turret while jogging the X up and down. It should be parallel with x movement. If not, loosen face bolts on turret and adjust rotationally. Once parallel, then shim as described in previous posts. (I too suggest leaving out the taper pins) next, onto the Z axis. Check the turret face with an indicator as you move Z. It should be parallel with Z. If not, loosen the 6 bolts holding it down (see maint. manual or parts book) and straighten it out. One final thing on the turret - centerline. Indicate the center of a boring bar holder with a co-axial indicator. Don't worry so much about the y direction since the machine has an eccentric bolt that can move the holder up and down on the face. Besides you've already done this by checking the turret slot for parallelism with X. Find the X center and Calculate zero in your zero offset page. Write this new number down in the data management card in the back of your machine so if someone changes it, you can go back to it.

Next headstock. I think there's at least 6 bolts holding it down. I like to use a brass or aluminum bar. Skim cut it about 1 foot and check for taper with a Micrometer. Use a dial indicator when moving the headstock to see how much you are moving it. Repeat until she's straight. Okuma usually considers it straight when it is below .0005/4" on X and .0005/12" on Z. Always shoot for better, you can hit it without fail even on beat up machines.

Getting tired yet? Last but not least you may want to indicate your chuck in too to make sure there's no runout. Runout caused balance issues and can cause runout in your parts even if it's only a few thousanths.

Good luck - I don't think you'll be bored for the day...!