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Thread: In Need Of Your Shop Wisdom

  1. #1
    Join Date
    Sep 2007
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    Wasilla, Alaska
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    Default In Need Of Your Shop Wisdom

    Hi Guys,

    Once again I visit the Lodge of my brothers in search of Light. I need a wee bit of your infinite wisdom.

    Ordinarily, the work I do on my lathe is not so critical that I need to use a 4-jaw chuck. Historically I simply chuck a piece of metal in my 3-jaw chuck, turn to size then part the piece.

    I recently purchase a piece of aluminum that's 2.5" OD X 12" length and I desire to keep it as close as possible to 2.5" OD. I have no aversion to reducing the OD by a few thousandths but I do have a problem with reducing the OD by .010". In this case that would be unacceptable.

    Using my new 4-jaw chuck for the first time I began indicating using my indicator which measures in .0005". I tried to pick as smooth a surface as I could find fearing every little bump and dip would be recognized by the indicator. And I was right to have this fear. Resigning myself to the fact that I was indicating a rather rough surface, I was happy getting the piece indicated within .001" near the free end. Problem begins.

    When I power-up the lathe, the end runs quite smoothly but the work that's closest to the chuck has an observable wobble. Moving the indicator near the chuck I re-indicated and re-adjusted the work until I was within .001". Great .... but now I have noticeable runout at the end. I'm faced with a .010" difference any way I go. I have not tried using a steady rest. I assume this would be advisable? Should I first indicate at the chuck and make jaw adjustments and then use the steady rest and indicate near the end to get the work running as true as possible?

    Since this was a piece of extruded aluminum that was pulled off the rack and shipped to me, should I assume this is as close as I will come (.010") to getting this work running true due to the rough surface? Seems like I should be able to do better than that.

    Both ends need to be faced off and I need to drill (bore) a hole through the entire length. My goal is to keep this piece as close to 2.5" OD as possible and get everything running true along the length of the piece. What are your suggestions in accomplishing this?

    Harold
    Last edited by hwingo; 02-16-2009 at 02:07 AM.

  2. #2
    Join Date
    Aug 2004
    Location
    Central Queensland, Australia
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    Default

    How big a hole needs to be drilled???

    Is the OD going to need to be turned in any way??

    You could try a cathead and steady??

  3. #3
    Join Date
    Aug 2003
    Location
    Southwest Georgia, USA
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    Chuck the part in the 4-jaw with the indicator near the outer end. Drill a center hole. Repeat for the other end. Mount the bar between centers, and indicate the OD in several places with the indicator mounted on the carriage. This checks the OD and also makes sure the tailstock isn't offset, which would result in a taper.

    If the amount you need to remove to true the OD is to your satisfaction, go ahead and true the OD.

    Proceed with your project as before, and report back.

    Roger

  4. #4
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    Default

    Quote Originally Posted by Ringer
    How big a hole needs to be drilled???

    Is the OD going to need to be turned in any way??

    You could try a cathead and steady??


    The largest hole to be bored is 1.75", the next largest is 1.5", and the smallest is .95". Refer to image.

    Harold

  5. #5
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    Default

    Quote Originally Posted by winchman
    Chuck the part in the 4-jaw with the indicator near the outer end. Drill a center hole. Repeat for the other end. Mount the bar between centers, and indicate the OD in several places with the indicator mounted on the carriage. This checks the OD and also makes sure the tailstock isn't offset, which would result in a taper.

    If the amount you need to remove to true the OD is to your satisfaction, go ahead and true the OD.

    Proceed with your project as before, and report back.

    Roger
    Thanks Winchman. I'll give this a go. I appreciate your reply.

    Harold

  6. #6
    Join Date
    Feb 2006
    Location
    SW PA
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    Is the piece straight to begin with? If it is, you should be able to hold a couple thou of size. You say .010 under is too much, and you are telling us that you have runout that is about that much, end for end.

    Bowed some.. You ain't makin' no 2.499 out of that.. Does it actually mike 2.500 over its length? You might have a couple to play with.

    Cheers,

    George

  7. #7
    Join Date
    Apr 2006
    Location
    citrus heights, ca
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    What has not been mentioned yet is to take a mic and check if the piece is round, it sounds like it may suprise You just how much it is out of round. As mentioned earlier it may also be bowed.

    Steve

  8. #8
    Join Date
    Aug 2004
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    Central Queensland, Australia
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    If it is 12" long and your spindle bore is smaller then 2.5 inches you will have to use a steady to bore it...

  9. #9
    Join Date
    May 2002
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    SE Texas
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    Round stock is not necessairly round. Or straight.

    In my limited experience, steel is worse than aluminum, but both are not all that accurate to size and may have low spots almost anywhere along the length. A reduction of 0.010" in OD (that's just a 0.005" cut) is not an excessive amount in order to get the OD uniform and I have seen stock that required more.

    I would first center punch both ends as accurately as I could. Then mount between centers using these punch marks and check for any excessively low spots. If there are any, mark the location(s) and how deep they are. The pattern of low spots will determing how much you must take off and where.

    You can then adjust the location of those punch marks and center drill both ends. Mount between centers again and reduce the OD until the lowest low spot is removed. You now have an accurate OD that you can base all the other operations on.

    If you really need a 2.5" OD, it is probably best to purchase oversized stock. This is available in some sizes and alloys without stepping up to the next fractional size.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  10. #10
    Join Date
    Dec 2003
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    Cranbrook,BC
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    Harold...I used to face the same problem you are having. It was due to my chuck jaws being out of whack.
    Get the far end true...the chuck end would be out....get the chuck end true..I'd have a big wobble on the far end.
    I always got around it IF I could center drill the far end when it was true. I'd then run that end on a dead center then I'd true the four jaw end.
    I kept the piece running on the center for all the truing operations...and for setting up the steady rest. Since then I've trued up the jaws for my four jaw and it's made life a whole lot easier.
    Russ
    I have tools I don't even know I own...

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