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machining technique for cylinder - help???

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  • machining technique for cylinder - help???

    I need to make a tube of cast iron..2 7/8" long, 1.000" ID, 1.3755" OD.
    Problem is,, I didn't think it through when I bought the material; I have a 3" long piece of cast iron.
    If I had a longer piece I could chuck it up and bore the ID and turn the OD with the same setup.
    OOPS!!
    Any suggestions to salvage this or should I just get another, longer piece of stock??? I have an 8" 4-jaw chuck as well as other "goodies" however, I'm using a 12" swing, 3in1 lathe/mill.

    [This message has been edited by rmatel (edited 08-27-2003).]

  • #2
    That's pretty thin wall for cast iron. Throw the 3" piece in the corner and buy a 5" piece.
    Free software for calculating bolt circles and similar: Click Here

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    • #3
      1st face one end.
      2nd reverse in lathe and face to length.
      3rd Leave in chuck from step 2 and bore and finish the bore.
      4th remove from lathe and proceed to turn an arbor with a sholder on one end and threads on other end. The arbor should be turned between centers and should be a very light press fit in bore. slide/press cylinder on arbor and fasten with the right size washer and nut.
      5th turn outside diameter and carefully remove from arbor.
      Done correctly you will have correct sized cylinder with a concentric bore.

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      • #4
        RMatel;

        1. Chuck in lathe drill/bore ID

        2. Remove from chuck and mount on expanding mandrel

        3. Turn OD remove from mandrel

        4. Chuck in 4 jaw and face ends to length.

        You end with concentric cylinder with ends 90* to finished ID/OD

        Thanks Keith
        Cheers Keith

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        • #5
          Or, if you don't mind spending the money, do as Stepside advised except spend $11.39 with Travers Tools and get a 1" mandrel that has been hardened and ground for turning between centers.

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          • #6
            You don't need any of that,if you have a bull nose center for your lathe,first true each end square,then bore to size,then chuck a piece of mild steel or brass and turn a 60*point on it,put your clinder between the fresh turned point and your bull nose,then turn your od using light passes of say .005-.010"on the radius and a .003"per rev. feedrate.If you leave the part a little long you can later face the ends again to final size,I have done countless bushings and bearings this way and have always had perfect results.
            I just need one more tool,just one!

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            • #7
              Weirdscience hit the bullseye on this one..You can turn between centers without using a drive dog, as long as your careful..i have done this many, many times with good results...you just need to make the tailstock a little more snug!! So basically, get your piece to the correct length, drill and bore, then mount between centers for the od....

              brent

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              • #8
                I'm with Stepside on this but thru my own experience the part does not have to be a press fir on the mandrel. Turn the mandrel in the chuck(it will be dead nut on center),
                make it .0005 to .0007 under the bore size
                and it will slide right on. Drill and tap the end and hold the part with a SHCS and washer.
                Lee

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                • #9
                  Center drill both ends and turn as wierd descibed. Then chuck in four jaw and indicate od till it turns true. Drill and bore. Check run out before finish pass. Wierd's way is just as good this is just doing same thing backwards.

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                  • #10
                    Of course, the easiest answer is to have a piece of material that you can chuck in the lathe and do it all in one setup. No fiddling with mandrels, centers etc.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      I hate to say it, but Brent and WS are right - but then so is Keith. I would use Keith's method - the first that came to my mind. Keiths method works every time - my sister could even do it...

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                      • #12
                        If you wish to be really concentric the fit on the mandrel is important. If you have an expanding mandrel use it. When I build a mandrel I like to turn it between centers and use a threaded portion and a nut washer combination to lock part on. That way you have both a headstock and a tailstock center for support.
                        Maybe I overbuild or maybe I am too fussy or maybe I just like to single point threads. I would go with all three. I usually have several mandrels from other projects hanging around---these are turned down until they fit the current need. When they get too small they go in the scrap bin.

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                        • #13
                          Thanks guys,
                          Lots of good thoughts. Concensus seems to be turn OD last on some sort of mandrel.
                          Thanx again,
                          Bob

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