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  1. #1
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    Feb 2009
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    Karana Downs
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    Default AL-320G Tailstock high

    I have just installed a new AL-320G lathe and a dial indicator on a drill chuck arbour in the tailstock shows that it is .05mm higher than the headstock. I believe that they are made slightly higher to allow for wear on the bed but is .05mm too much? If so, should I remove some material from the base of the tailstock or is this not significant enough to worry about? Will this difference affect drilling centre holes with the centre drill chucked in the tailstock? If material should be removed what is the best way to do this bearing in mind I don't have a mill or surface grinder etc? I have flattened the soles of metal hand planes using wet & dry paper on glass. Would such a method be OK for the tailstock? Thanks, Kevin

  2. #2
    Join Date
    Aug 2011
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    Melbourne
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    Default

    Hi there,

    This will no doubt be the first of many varied replies! Is the TS 0.05mm high with the quill fully extended or retracted? Is the TS clamped down to the bed when you took these measurements? Has the bed been levelled?

    Is the TS high BUT parallel to the bed or is it sloping up?

    Did you receive one of those test certificates, if so what does it say in the relevant test? Is it within tolerance?

    It does sound like you are reasonably new to the world of machining. So personally I would not mess with it! Such a height difference will not create that much of a taper when turning with the TS as support until you get down to very small diameters. For example a tool height variation of 0.05mm on a 10mm diameter workpiece will produce a difference in diameter of about 0.1uM. If turning between centres then you would vary the TS until you got to the required parallelism anyway. If the TS is higher but not parallel then you can extend or retract it until you get it spot on. Remember the position on the quill and use it to your advantage if that level of accuracy is important.

    A few years ago I would have been inclined to do a similar measurement and be hell bent on "fixing it" but I'm of the opinion now that such things are generally not needing fixing, it's best to leave it. I doubt it will ever create an issue where it will affect your work quality. If ever it does, deal with it then.

    Congratulations on your new purchase!

    Edit: I just re-read my post. I reworded the reference to the tool height!
    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  3. #3
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    In between looking after two sicks kids, I just thought of something else to add.

    Your method of measurement can also have a bearing on the results you found. If your setup is not extremely rigid, then in some cases the droop from gravity can create a situation where it may affect your reading. Perhaps making the result look worse than it is.

    Back to sick miserable kids!

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  4. #4
    Join Date
    Jun 2007
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    sydney ( st marys )
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    Default

    I would suggest at present leave it alone.

    Use the machine and if you get the results you desire call it good,if not then delve into ways to correct your concerns.

  5. #5
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    Aug 2008
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    near Rockhampton
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    Default

    I would not touch it, unless I knew what I was doing...

    And no 0.05mm too high if it actually is that is insignificant...
    Gold, the colour of choice for the discerning person.

  6. #6
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    Aug 2007
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    The al320 has a two part tailstock. It is not uncommon, on a new machine, to find paint and other gunk in between the mating surfaces of the TS upper and lower castings. Separate the parts and carefully clean, and if necessary deburr the edges. Then trassemble and check again - the problem may have disappeared.

    The TS is usually supposed to be about 0.01 to 0.02mm high, to compensate for workpiece sagging when turning between centets. 0.05mm high is not that much a problem.

  7. #7
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    Aug 2011
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    I dug out my "test certificate" and it states that the maximum centre height difference between TS and HS is 0.06mm.

    20140718_125130.jpg

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  8. #8
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    Oct 2007
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    Sydney
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    The Schlesinger Standard for vertical on a lathe like this on the TS to HS is normally 0 - 0.02 mm, with a requirement for the TS to be higher than the HS. Naturally lathe manufacturers are free to set whatever tolerances they choose, and there's no law to say a tool is no longer considered "a lathe" just because it doesn't meet some old German guy's standards.

    Having said that, if it was 0.05 mm I'd like to know how that was measured, and would still recommend leaving it alone.

  9. #9
    Join Date
    Jul 2013
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    I have an AL-320G lathe and I definitely had a problem with tailstock alignment straight out of the crate.
    As Cba Melbourne stated this lathe has a two part tailstock and it would be worth pulling it apart to check what is going on inside.
    I found in my case that the hole through the base part for the clamping bolt appeared to have been hacked out with an axe and there was a huge burr around this hole which was jacking up the top part of the tailstock and causing severe misalignment. I carefully filed off the offending burr and found that the tailstock was then in correct vertical alignment.
    Hope this helps.

    Alan.

  10. #10
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    Quote Originally Posted by OLCDOG View Post
    I have an AL-320G lathe and I definitely had a problem with tailstock alignment straight out of the crate.
    As Cba Melbourne stated this lathe has a two part tailstock and it would be worth pulling it apart to check what is going on inside.
    I found in my case that the hole through the base part for the clamping bolt appeared to have been hacked out with an axe and there was a huge burr around this hole which was jacking up the top part of the tailstock and causing severe misalignment. I carefully filed off the offending burr and found that the tailstock was then in correct vertical alignment.
    Hope this helps.

    Alan.
    Out of curiosity. Was it shipped with one of the Chinese certification test sheets some here put so much faith in? ie the ones that are the very last thing the machine goes through before being crated. If so, what did it say about the tailstock height?

  11. #11
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    Quote Originally Posted by Pete F View Post
    Out of curiosity. Was it shipped with one of the Chinese certification test sheets some here put so much faith in? ie the ones that are the very last thing the machine goes through before being crated. If so, what did it say about the tailstock height?

    A lathe is actually aligned whilst being assembled. The inspection record is being filled in whilst the assembling progresses. On the fly so to say. At the end of the assembly, the machine is ready for crating. I believe it is only for the very expensive lathes, those that we would dare to call "toolroom lathe" without getting red, that the inspection values would be re-measured a second time before crating. Very large lathes are no doubt still installed by the maker and an inspection record is filled in after installation at the customer's site.

    Now, I would personally find it extremely interesting and helpful, if we could somewhere collect as many scanned inspection records as possible from different Chinese lathes up to say 1000kg weight, and mills too. Actual owners could compare them across, the general public looking to buy a new machine would get an idea what to expect, and we could compare with the Schlesingers book "testing machine tools". This work is still what is used by each and every lathe maker around the world, all ISO and EN and ANSI and AS standards dealing with machine alignment are based on Schlesinger's work, it still is a stock reading staple for every mechanical engineering student. It is indispensable reading to fully understand a lathe inspection record.

  12. #12
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    Every inspection record I've ever seen on a Chinese machine is filled out with the same pen and the same hand writing. That guy sure must be a great assembly worker

    Regardless of pointless semantics, the inspection record is the condition that machine should be in when it ships. If there's paint/burr/encrusted rice then clearly it would never have passed that inspection, regardless of when it was done. Burrs don't suddenly grow legs and crawl in between castings. The whole point is to not presume that just because an inspection record says something, that's the accuracy of the machine now. It may not be, nor in some cases may it have ever been!

  13. #13
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    Jul 2011
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    Quote Originally Posted by Pete F View Post
    Every inspection record I've ever seen on a Chinese machine is filled out with the same pen and the same hand writing.!
    It would be interesting to see who signed off on Simons test chart a few posts back. Inspector A, B or C?

    -Phil

  14. #14
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    Quote Originally Posted by Machtool View Post
    It would be interesting to see who signed off on Simons test chart a few posts back. Inspector A, B or C?

    -Phil
    Hi Phil, At work ATM but I'll attach the entire "test certificate" in a day or so just for s and giggles. I keep it for reference in case I dismantle it. At least if I realign it to the so called specs I know I'll have a machine that's probably better than when it was new! Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  15. #15
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    G'day Simon, irrespective of the manufacturer the test process normally complies with the bog standard Schlesinger standards, even though the actual numbers it seems may well vary. Some of the tests can be done without test bars etc if you don't have them by using some "cheats", but some you will need accurate test bars even to see if the lathe meets the specifications, never mind actually varying any alignment.

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