Truing square stock in a 4 jaw independent chuck?

Discussion in 'General Engine Discussion' started by Twmaster, Dec 7, 2009.

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  1. Dec 7, 2009 #1

    Twmaster

    Twmaster

    Twmaster

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    I'm scratching my head here. I have some 1" square I need to work on. Cannot quite wrap my head around how to indicate this so it is trued in the chuck. Each time I try to rotate the part the indicator ends up physically moving making measurements pointless.

    A search of google was useless.
     
  2. Dec 7, 2009 #2

    Tin Falcon

    Tin Falcon

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    This has been discussed before but poblaby the easiest way is to locate the center and center punch then indicat in on the punch mark with a pump center. the other way is to retract the plunger of the indicator as you turn the piece and you may want to set a little level on top to keep things square.
    You can often get close just by eyeballing it in turn the chuck by hand and bring a bit close to the part then turn it 180 degrees you will se a gap adjust out 1/2 the gap then turn 90 degrees repeat until close then finish with above methods.
    tin
     
  3. Dec 7, 2009 #3

    Twmaster

    Twmaster

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    D'oh! Pump Center.....

    I was just looking at those on Tallgrass Tools web site a day or two ago...
     
  4. Dec 7, 2009 #4

    shred

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    Lacking a pump center, you can make do with a regular dead center trapped between the tailstock and the pop mark and indicate off that. The Bogster and others posted that one here a long while back.

    Here's a few of the old threads:
    http://www.homemodelenginemachinist.com/index.php?topic=6407.0
    http://www.homemodelenginemachinist.com/index.php?topic=5034.0
    http://www.homemodelenginemachinist.com/index.php?topic=596.0 (the center-in-center trick is at the end of this one)
     
  5. Dec 7, 2009 #5

    mardtrp

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    Why not just stick it in the 4 jaw and tighten down the jaws a bit, now bring the tip of whatever tool you have in the toolpost, up towards the square bit. Start to rotate the chuck by hand and watch the square corners in relation to the tooltip.
    Adust the 4 jaws as nessesary, until ALL the 4 corners are just touching the tooltip, when that happens, it's dead centre.

    Try it, you wont believe how simple it is to do, until you give it a go.

    Oh, dont bother with any dial indicator, not unless you dont like the thing, it's a good way to ruin them, by trying to true up a bit of square with them. :big:

    Mark
     
  6. Dec 7, 2009 #6

    rake60

    rake60

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    There is the simple old method.
    The indicator tip needs to be as close to on center as possible.
    With the tip against one flat rock the chuck back and forth to find
    the low spot and zero out the indicator. Pull the needle back to clear
    the piece and rotate it 180° Lower the tip to that flat and again
    rock the chuck back and forth to find the low spot.
    If you indicate to the 4 sides low spots the stock will be centered.
    If the stock is too big to clear the indicator needle by puling it back,
    mount the indicator on the cross slide and move it back out of the way
    to rotate to the opposite side.

    Rick
     
  7. Dec 7, 2009 #7

    Deanofid

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    Howzat?
    Been truing square in a four jaw with the DI for years. Haven't hurt one yet.
     
  8. Dec 7, 2009 #8

    jonesie

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    i agree with rake 60 use the indicator as he says i always set my indicator that is on my surface gage on the carriage then move it back out of the way.there will be times that just getting close will not be good enough and doing it this was you will be right on center every time. i have never damaged an indicator in30yrs +doing it this way
    . good luck
     
  9. Dec 7, 2009 #9

    mklotz

    mklotz

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    Make a "flapper" for your DI as shown here...

    http://www.homemodelenginemachinist.com/index.php?topic=3820.msg39062#msg39062

    and you won't need to worry about damaging the instrument.

    I made mine so it was one-screw-detachable from my regular 4J centering fixture.

    Don't be tempted to center using the edges of square stock. Work off the flat surfaces. The edges are often dented and damaged.
     
  10. Dec 7, 2009 #10

    Twmaster

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    Thanks again gang. Lots of reading. Great ideas! I just happen to have a coule of centers I can use temporarily until I can make a pump center.
     
  11. Dec 8, 2009 #11

    tornitore45

    tornitore45

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    For "close enough" work I would use Mark approach.
    For a part that is already machined and need accurate centering I use a modified version of the flapper.
    The pump center technique is no more accurate than your ability to scribe and punch a center based on the diagonals; with rounded corners this is even more sloppy.

    I place a piece of old saw blade (tooth ground off) in the tool post laying on top of the corner at its highest spot
    place the indicator to swing just a little when the corner lifts the reed.
    Smooth no damage to the indicator, works also for threaded or rough parts like HRS when you have little oversize.

    Mauro
     
  12. Dec 8, 2009 #12

    itowbig

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    mauro could u please post a pic of that setup th_wwp

    i do like mark does my self its pretty darn close Thm:
     
  13. Dec 8, 2009 #13

    jonesie

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    you people are making it way do hard just use your indicator on the carriage and swing the low spot it is not hard and after you have done it once or twice it is fast and you will be right on center with out a lot of do -dads to make or use can not get any easier
     
  14. Dec 8, 2009 #14

    mklotz

    mklotz

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    jonesie,

    There are no categorically right or wrong ways to do anything in the home shop. Hearing other people's approach to a given problem often sparks new ideas and creativity.

    Let's let the ideas flow without criticism. If it doesn't suit you, ignore it - but do so silently.
     
  15. Dec 8, 2009 #15

    jonesie

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    ok sounds good just thought the shortest distance between two points was a straight line, just trying to help, but with 30+yrs as a moldmaker i will keep my thoughts to my self
     
  16. Dec 8, 2009 #16

    doc1955

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    I totally agree with you Jonesie that is the best way to indicate square stock in dead on. And I agree once you have done it you will see how easy it really is. I also use this concept of swinging in an edge on the jig bore when you are trying to hold very tight tolerances. It will put you spot on every time.

    I have had over 35 years in a tooling shop and have done a lot of progressive dies form dies and blank and pierce dies. And if you need to be spot on my money is on this concept.
     
  17. Dec 9, 2009 #17

    Twmaster

    Twmaster

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    Jonesie..

    Please explain this procedure in English. You have my attention.
     
  18. Dec 9, 2009 #18

    jonesie

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    tw set your chuck jaws with a scale somewhere close to the size of your block then put in the block and lightly tighten them up.then set up your indicator on a surface gage and set up on the carriage them more the carriage up to the piece and on to the part . then get a touch with the ind. and then move the chuck back and forth to find the low spot then move the carriage away and rotate the chuck 180 degrees and move ind. back on to the piece being careful that you do not hit the ind. if you are to far off then swing the chuck again and see where the low spot is then move the piece with the jaws until they read the same. then do the same for the other 2 sides with a little practice you will be suprised how easy and fast you can do it . scale the jaws as close as you can and you will be able to ind. the piece in fairly easy and fast and you will be right on center not just close. when you first start to ind. the part you might want to set it close on one side and then rotate the chuck 180 and see which is the high side . it is also easier to do the first few times by using an indicator with alot of travel. try it and you will see how to do it , just remember that you have to move the carriage back so the indicator is off the piece before rotating 180 degrees or you will ruin your indicator.good luck hope it makes sense
     
  19. Dec 9, 2009 #19

    Twmaster

    Twmaster

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    Jonesie...

    Thank you. I have a 2" travel DI. It looks like the setup for the DI needs to be pretty rigid to keep the indicator from moving while you are turning the chuck...

    Very simple. A DI mount for my tool post would be a snap.
     
  20. Dec 9, 2009 #20

    jonesie

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    tw just remember you need to move the carriage back when you rotate the chuck180 deg. to do the other side.also after you have done it a few times you will find that you can eye ball it close and you will not need to but much pressure on the indicator needle. i just use an indicator with .060 travler an interrapid.i mount it on my surface gage and just set it on the carriage. remember also when setting up a finished piece to wk on after you get it centered you need to run the indicator on the front face to make sure it is also running true.
     

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