Lathe Levelling vs Live Center - Page 2
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  1. #21
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    Quote Originally Posted by Derek Smalls View Post
    It still amazes me that this topic has been covered as many times as it has, the correct and only logical procedures have been explained by people who do this stuff for a living, and yet so much misinformation is constantly regurgitated.
    Tell me about it, thought we were in the Southbend forum for a minute! All we need now is for the self proclaimed king of all pros to come in and suggest shimming the headstock, then the thread will be complete!

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    Quote Originally Posted by JCByrd24 View Post
    If you are going to turn a longish part between chuck and center, how do you drill the center hole, choke up and drill it first, then pull it out and rechuck, or hang it out and drill it hung out?
    For over-the rail axles, standard gauge, we drilled them on an ATW 8-foot radial drillpress. The 5 foot ATW and 3 foot CB were tall enough for mine rail car, narrow gage. Not tall enough? Hang it off the traveler and scoot it over to where one of the HBM can get at it.

    The issue is not placing a center divot accurately. That's trivial, large ATW, tiny Walker-Turner - even hand-held portable tools, wisely used. Worst-case, an imperfect one gets you to where you can true a track for a steady rest. Then you recut a better centre divot ON the lathe.

    The issue is where the live or dead centre in the LATHE is positioned, relative to the axis of travel of the cutting -tool atop the bed and carriage.

    "Proper" correction is tedious, needs done in the metal, needs done WELL, and has been covered to the "done to death" level, and "right here on PM".

    "Temporary" correction really CAN be as simple as careful use of a sliver of paper or foil.

    It isn't "right", but it can WORK.

    Some days it is all you have in the time available, even on a lathe you DO "own" and ARE "allowed" to do the full and proper restoral of.

    "Some day". As-in when time and workload permit. It's mostly labour, after all. Not a lot of money nor a huge expense in materials to it.

    But the TS is "out of action" from the time a proper rebuild is commenced until it is FINISHED, or "mostly so". It can be done in stages, but that makes it harder, not easier, to get it right. Better to just block out the time and go for it, end to end.

    If you are NOT going to commit the time and effort to doing a TS rebuild "proper"?

    Better to not even START.

    Get you some shims, ban cameras in your shop, JFDWT as an admitted 'monkey patch" and make no fuss about it. As said, tens of thousands of "employees" over long, long years never had any other choice on worn-out "company" lathes. OTOH? We were paid by the HOUR, so why would we go on strike over it?




    BTW.. mere presence of a chuck does not rule-out turning "between CENTRES".

    Turning or truing-up a bespoke centre held IN a chuck is easily as common as use of a centre in the spindle bore. And... removes all those objections about bending, etc.

  3. #23
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    Starting place is check to see the head and tail center line is the same, check horizontal and vertical. 10 minuets.

    Be sure the live tail center is true running true .001/,0002 or better.. 5 minuets.

    Check to see head and tail center line stays true (face and top) as the tail is moved along the bed.another 10 minuet.



    Running a thin part 30" long can be a bugger out of a chuck and on a tail. but not likely small at the tail end...and tapering evenly suggest a stout part.

    And as Derek suggested you may need a new garage door to fix the car and the lathe.

  4. #24
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    I’m afraid my help turned south in this thread. I’ve been studying Utube vids on the matter. The Celtic has an adjustable tailstock, and I am pretty sure that’s the issue. TOT has a video where his lathe had an almost identical issue. In the description he showed that raising the rear right leg would counter the taper...but then he raised the right front to fix it. The only way that makes sense is if the tailstock was out.

    My tapered part was 2.5” 304 stainless, and I really can’t visualize how using a chuck is a factor?!?

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    Quote Originally Posted by CJD View Post
    I’m afraid my help turned south in this thread. I’ve been studying Utube vids on the matter. The Celtic has an adjustable tailstock, and I am pretty sure that’s the issue. TOT has a video where his lathe had an almost identical issue. In the description he showed that raising the rear right leg would counter the taper...but then he raised the right front to fix it. The only way that makes sense is if the tailstock was out.

    My tapered part was 2.5” 304 stainless, and I really can’t visualize how using a chuck is a factor?!?
    In a more perfect world ALL tailstocks would be more adjustable than most are.

    "Most" ass u me there will never be any wear of quill/ram, will never be any wear of the base, and provide ONLY the to-from operator, horizontal plane movement to be utilized for INTENTIONAL "set over" to do long shallow tapers a-purpose.

    A better design? Add adjustment for vertical rise to offset wear.

    Why not JF DO that?

    Pragmatism.

    Wear is slow, even predictable.

    Operator mis-alignment is fast and Unpredictable. More likely to f**k it up than LINE it up.

    Compromises? Well. Humans we are dealing with, here.

    Ever notice that when there are TWO rolls of bum-fodder, both go down to the last sheet, same time? And that humans don't even LOOK before they take a dump, only AFTER? Classical "Oh SHIT!" moment, yah?

    How d'yah expect anybody to PAY for a saner design of tailstock if they can't even be bothered to see to it their own tail is stocked?


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    Chuck can have rotational error and a simple run an indicator there while hand turning the part will tell what that is.
    A 4 jaw chuck can be adjusted to near zero but if it is a poor chuck can have wobble from error in the jaws.
    A tail live center can be rotating out of round so set your indicator on it when it is loaded with some pressure.
    The head and tail have to be at the same height and center line.
    Everybody here is saying that, so start here.
    Then progress to the next thing to check...
    Quick trick is to turn a slug in your head stock (any old chunk of material) the same diameter as your tail quill and then touch off those two places with using your DRO numbers and something held at the tool bit position. This should get you better than .002
    While you are doing that strike an indicator across the top of the two places just to see how your bed condition and tail height are at the one place.
    Strike the indicator across your tail quill at close and out to see how flat is your tail.
    Write down your findings so any adjustment might come from thought and real numbers.

    Some times a tail quill can run higher and lower as it is extended or just be at a slight angle to the bed, so good to have the number in your notes.This is not the cause of your problem but good to know your lathe.
    Last edited by michiganbuck; 01-23-2020 at 05:52 AM.

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  9. #27
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    Quote Originally Posted by CJD View Post
    I’m afraid my help turned south in this thread. I’ve been studying Utube vids on the matter. The Celtic has an adjustable tailstock, and I am pretty sure that’s the issue. TOT has a video where his lathe had an almost identical issue. In the description he showed that raising the rear right leg would counter the taper...but then he raised the right front to fix it. The only way that makes sense is if the tailstock was out.

    My tapered part was 2.5” 304 stainless, and I really can’t visualize how using a chuck is a factor?!?
    First, I don't want it to be lost that I agree your TS adjustment is likely the issue. The point I was trying to make is that if you don't know the condition of some other things, and if you are turning between chuck and TS, you may end up chasing your tail.

    There is a distinct difference and set of issues and resolutions between turning a taper when held only in the chuck, and turning a taper when supported by the TS. That's why I asked how well it turns when using only the chuck.

    The process of adjusting legs as you describe in the video is usually done to fix taper when held only in the chuck. Basically fine tuning the bed twist after leveling. TOT usually is pretty on top of things so I'd be surprised if he's (un)twisting the bed to adjust for taper with TS support. That's not necessary. If the lathe is setup and turns true without the TS, you just adjust the TS to make it turn true with the TS, not twist it differently.

    Regarding turning between chuck and TS. Lets assume your lathe is setup well except your TS is out of line. You chuck up your 2.5x30" bar held on theoretical CL by the chuck. Your TS center now doesn't align with your center hole because your TS is off. It'll go in, but your pulling your piece out of line with your chuck, stressing the work, chuck, and TS and all associated bearings with each revolution. In a less rigid workpiece you will see odd results in the cut. Like hourglass or egg shapes, etc. This is why you ideally turn between centers, especially if you are troubleshooting a taper. Or hold on to just the end of the part in the end of the jaws of the chuck, so you're imparting as little stress as possible.

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  11. #28
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    Alright...very good info. Thanks for getting back on point for me. I'll post the results once I have...it sounds like a full day or so...to work on this.

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    Quote Originally Posted by CJD View Post
    Alright...very good info. Thanks for getting back on point for me. I'll post the results once I have...it sounds like a full day or so...to work on this.
    More like TWO days, and growing .. because you'll want to think on the first set of data, then go back and confirm your suspicions, next day. Then find more in the details, etc.

    The good news is that right away you'll be able to start "compensating".

    That leads to even MORE understanding. Keep notes, hold open the questions as well as answers, and in the fullness of time, you'll be in a far better position to plan a rebuild. Or not.

    As importantly - better equipped to take a decision as to whether - and what parts of it are actually worth the downtime, labour, and spend.

    My own case? NONE of it. "Compensate" I HAD to do. Compensate I can still do.

    From probably US Civil war to end of the "all manual" era and the shift to NC/CNC. MANY, then MOST, then nearly ALL hired-hands operating machine-tools they did not OWN for their wage had to deal with progressively declining "newness" and increasing uncorrected wear in the machine tools they HAD under their hands.

    The as-new specs of ten, twenty, forty, and more years earlier became but numbers on decaying old paper, what with wartime use and low/no maintenance since new.

    "Wise and wealthy" firms sold-off machinery and upgraded. Each next owner down the "food chain" made-do with a more and more worn machine tools.

    Guess who is at the bottom of that long decline?

    Got it in one. We chickn's in the here and now!

    What I call "smallholders".

    Some are "revenue" shops, but no longer "mainstream". Their bizness cannot justify the spend on modern CNC and earn it back rapidly.

    Other are retirees. Even hobbyists. Or "NOW we are" even if former career machinists.

    The"good news"?

    If there are a few thousand rebuilders at comparable skill to the world's best and most well-known?

    There may easily be a few hundred MILLION... "worldwide", USA to dirt-poor corners of the world ..who can Just Firmly Do whatever it takes in the way of "compensating" well-enough..... to get good parts off worn-out machine tools.

    Because it's what they HAVE, not what they WISH they had.

    Learn that first. Master what you HAVE.

    Rebuilds not only become easier and wiser. They may become not worth the bother.

    Because you've taken the savings in time and money to go and add ANOTHER worn-out but still interesting and still USEFUL machine-tool.. with which you will ALSO learn to do good-enough work.

    That's what earns the respected badge of "machinist".

    A problem solver, not a problem-creator.

    Any damn fool - of which there is always a SURPLUS - can do good work on a "perfect" machine - of which there is always a SHORTAGE.



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