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Lathe Alignment Issue

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by TDIZook, Mar 18, 2017.

  1. TDIZook

    TDIZook United States Swarf Registered Member

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    Hi all my name is Rice and I'm new to the forum,I have searched a little and could
    not find anything related.
    This lathe was given to me a few weeks ago,it is a 12" Craftsman.
    Here is the issue:
    Tool is centered enough to not leave a nipple...
    The mark you see is a center not a nipple.
    [​IMG]
    Center drill and live center are very close,no wiggle when drilling...
    [​IMG]
    But when the tail stock is moved to the end of the bed,the tool and live center are way off.
    [​IMG]
    I feel this is not right(???) and the only thing I can think of would be the head is not 90ยบ to the bed.
    Any advice will be greatly appreciated,
    Thanx
     
    Last edited: Mar 18, 2017
  2. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    From your first and last photograph, it appears that your bit is about the same amount below the spindle center. The absence of a nub isn't the best indicator of tool height relative to the spindle axis. Many times, the nub will shear off under cutting pressure.
    I would not expect to see much in the way of vertical misalignment on your lathe. The headstock is firmly mounted and it would be difficult to create a vertical twist. The tailstock doesn't see a lot of movement so wear should be minimal.
    Properly, the lathe alignment should be checked and done in a logical order; crossfeed travel perpendicular to the spindle axis, spindle axis parallel to the ways both horizontally, and vertically then the tailstock alignment. I give that order because the only way to correct misalignment of the crossfeed on my lathe, at least, is by rotating the headstock. A misaligned crossfeed will cut a dished or domed face. I had erroneously rotated the headstock to correct cutting a taper and ended up with a domed facing cut. Once the lathe faces properly, you can check for the ways being parallel to the spindle axis. The classic method is the two collar test but I prefer Rollie's Dad's method. It is capable of checking the alignment in both the vertical and horizontal plane. Misalignment is typically corrected by shimming the tailstock to change the twist in the bed. Finally, the tailstock can be checked/aligned. Using a modification of Rollie's Dad's method with centers, you can check the tailstock. Corrections in the horizontal plane are easily done by the centering adjustment screws. Vertical adjustment can be done by shimming the interface between the tailstock and the base. You should also check for an angular misalignment. This will be evidenced by a change in vertical or horizontal alignment of the tailstock as the quill is advanced or withdrawn.
     
    rdean and JR49 like this.
  3. TDIZook

    TDIZook United States Swarf Registered Member

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    Thank you for the quick reply,I will do some more measuring in the sequence you mention
    and check out Rollie's Dad.
     
  4. TDIZook

    TDIZook United States Swarf Registered Member

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    One more photo,this shows how far off the tool becomes in 9.5"
    The nipple is about 3/32 in width.
    [​IMG]
     
  5. intjonmiller

    intjonmiller United States Active Member Active Member

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    Just to add one other option to the list, a precision ground test bar is a good thing to have to test the alignment (horizontal and vertical) of the spindle/headstock with the ways. I have an MT3 test bar for that purpose. I went with a cheap import but it is very well made and makes checking that alignment very fast.
     

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