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  1. #1
    Join Date
    Nov 2006
    Location
    Heidelberg, Victoria
    Age
    79
    Posts
    2,251

    Default Truing square bar in a 4 jaw chuck

    Gentlemen,

    There must be a simple way of setting up say a piece of 12mm square bar in a 4 jaw chuck. I have just done it, but it took half an hour touching each corner of the bar with the turning tool, and adjusting each jaw until the tool just nicked each corner.
    Very tedious and not really spot on.

    I do have an indicator dial with magnetic base, but couldn't figure how to reference it to anything.

    Any ideas?

    Regards,

    Ken

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  3. #2
    Join Date
    May 2003
    Location
    Perth WA
    Posts
    3,784

    Default

    Hi Ken
    Go to this link and then select "Indicating a Part". There is a video on that link at the bottom that shows how to do it. As for positioning the dial gauge anywhere the mag base will sit and it is solidly mounted.
    This site is excellent and worth a browse.
    http://www.jjjtrain.com/vms/lathe_4j...e_4jaw_00.html
    Cheers,
    Rod

  4. #3
    Join Date
    May 2005
    Location
    Newcastle
    Age
    72
    Posts
    3,363

    Default

    Ken when I was still at sea and using a lathe and 4 jaw chuck we use to keep a white painted board with a straight black line drawn across it , place this on the bed of the lathe under the chuck and the square stock and move your head so the edge of the square section is in line with the line. Spin the chuck by hand and you can see which way out you are, then adjust chuck accordingly by loosing one jaw then nipping it up again then tighten the opposite jaw the movement is minimal but thats what you want when making final adjustments.
    For a final check set your dial gauge to one face just pull the tip/plunger back out of the way and turn to the next flat etc but you will find that you can get remarkably accurate with the board and you eyesight with practise
    Ashore




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  5. #4
    Join Date
    Oct 2002
    Location
    NSW
    Posts
    1,610

    Question

    I saw a tip about realigning the tailstock (after moving it for taper turning) which might be adaptable here...

    The tip was:
    Before moving the tailstock part the end, say 1 cm, off a bar.

    To put the tailstock back in position, chuck the bar up, and hold the parted off piece against the end by using the tailstock.

    If you could feel the discontinuity where the bar met the parted off piece, the tailstock was out of alignment, so adjust it until you couldn't feel the join.

    I'm wondering if you had a 12 mm diameter short piece with a centering hole, could you hold it against the end of the 12mm square bar with the tailstock, then feel the 4 sides of the square bar to check if they are aligned with the side of the 12mm round?

    Cheers,
    Andrew

  6. #5
    Join Date
    Jun 2007
    Location
    sydney
    Age
    64
    Posts
    3,566

    Default

    hello i feel if your going to use a dial indicator to set up your block,set the block as best you can by eye or scriber point or what other means you choose,after setting this way bring your dial into touch a face of your block,block should be as vertical to bed as possible,and dial should be at the outer most end of work piece,have dial on cross slide,bring dial into touch job and advance or feed in cross slide a distance that your happy with,zero dial take note of how far you have wound it in. Then retract dial and rotate job 180,bring dial back in adjust chuck to suit,do this for the other opposing flats.(if you dont want to keep winding the cross slide in and out pull your plunger back on your dial and rotate job,if you use this method just remember to pull the lplunger back)

  7. #6
    Join Date
    Jul 2007
    Location
    Metford
    Posts
    19

    Default Setting up square bar in a 4 jaw chuck

    Line up the lathe tool with the EDGE of the square bar, not the corners.

    start by setting the chuck jaws roughly by uning the concentric lines on the face of the 4 jaw chuck. this puts you close to size & symetrical.

    You should be able to set up a peice of square bar in your 4 jaw in a couple of minutes & really close to centre.
    If you're needing to be really fussy, face the end of the square bar once you've set it up as above.
    Then you can measure with your vernier from edge to centre to check how close you are.
    Surely within about 0.5mm will be close enough for a hell of a lot of jobs?

    How did you go with this ?

    Tom

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