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Machining pipe conundrum

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  • Machining pipe conundrum

    I need to machine both ends of a piece of 1 1/2" pipe two accept roller bearings for a axle.
    My plan was

    1 - to put a temporary center in the end of the pipe (I don't have a bull nosed center), with a center drilled in it, for the tailstock support, my lathe doesn't have a big enough spindle bore to take the pipe.

    2- with one end in the chuck and the other supported by the temp. center to turn the OD of the pipe, at the end, for the steady rest.

    3- mount steady with outboard end of pipe on it.

    4- face and bore the end to fit the bearing.

    5- turn end for end and repeat.

    Now why this won't work. Pipe isn't round or straight inside or out, at least not by machining standards. While I may get the ends square and bored perpendicular to the faces, it is extremely unlikely that this method will result in the axis's of the bearings, once installed, being inline let alone parallel. Because of the inaccuracies of pipe, putting a temp. center in the pipe won't put the tailstock center inline with the center of the pipe so all machining will be off center.

    Any ideas on how to do this right.
    The shortest distance between two points is a circle of infinite diameter.

    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

    Southwestern Ontario. Canada

  • #2
    Use DOM tubing.
    ...lew...

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    • #3
      Center and hold the pipe with a temporarily modified follower rest. Mount a boring tool in the four jaw chuck so its off center and sweeping through the bore dia you need. Support the loose end of the pipe in the steady rest.

      Dunno? Just thinkin out loud JR

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      • #4
        Originally posted by Lew Hartswick View Post
        Use DOM tubing.
        ...lew...
        +1
        In my experience, BIP is not the easiest material to machine. It is kind of gummy.
        If I was going to build your project DOM tubing would be my choice also.
        Dan.

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        • #5
          If you had a cathead..you could eliminate step 1 ... just centre it of the cathead using the steady rest as step 2 .

          You could add the extra step of creating a steady rest bearing surface ,so you could remove the cathead , then re centre and machine the actual bearing surfaces.

          Hack admission: I have in the past used an old geased up tailstock mounted chuck as a three prong bull nose...while machining the steady rest bearing surface at the chuck end...but it wasnt for anything important.

          Rob

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          • #6
            Use a four jaw chuck. A steady rest and the center you made for the end of the pipe. Set up the pipe in the four jaw the other end supported with the center. Adjust the four jaw so the pipe runs near true. Turn a band on each end of the pipe that is the same size for the steady. Install the steady at the chuck end and adjust to fit, now move the steady to the tail stock end. It should fit the band without adjusting. Remove the tail stock and bore for the bearing. Reverse the pipe in the lathe. Put the steady on the band at the tail stock end. Adjust the four jaw so the the band now at the head stock is running true then bore the tail stock end to size.

            Bob

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            • #7
              DOM tube is out, it is a project for a friend and he gave me pipe.
              The shortest distance between two points is a circle of infinite diameter.

              Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

              Southwestern Ontario. Canada

              Comment


              • #8
                Originally posted by Lu47Dan View Post
                +1
                In my experience, BIP is not the easiest material to machine. It is kind of gummy.
                .

                I have the opposite experiences. BIP is quite ductile and machines beautifully -almost mirror like. I use carbide and a fairly high sfm.

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                • #9
                  Cheat!! Bore both ends a few thou oversize. Get a shaft that is a good fit to the i.d, of the bearings. Coat inside of bored recesses with Loctite, drop bearings into place and immediately insert the "alignment" shaft. Let cure 24 hours. Works like a charm.
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

                  Comment


                  • #10
                    Originally posted by lakeside53 View Post
                    I have the opposite experiences. BIP is quite ductile and machines beautifully -almost mirror like. I use carbide and a fairly high sfm.
                    I'm in the "it's kind of gummy" camp..... never got a mirror finish on pipe or 1018 without grinding. You must have that thing spinning fit to take off.
                    CNC machines only go through the motions.

                    Ideas expressed may be mine, or from anyone else in the universe.
                    Not responsible for clerical errors. Or those made by lay people either.
                    Number formats and units may be chosen at random depending on what day it is.
                    I reserve the right to use a number system with any integer base without prior notice.
                    Generalizations are understood to be "often" true, but not true in every case.

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                    • #11
                      Put a center in both ends, and turn between centers with a lathe dog to drive it.
                      ----------
                      Try to make a living, not a killing. -- Utah Phillips
                      Don't believe everything you know. -- Bumper sticker
                      Everybody is ignorant, only on different subjects. -- Will Rogers
                      There are lots of people who mistake their imagination for their memory. - Josh Billings
                      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                      Don't own anything you have to feed or paint. - Hood River Blackie

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                      • #12
                        Originally posted by J Tiers View Post
                        I'm in the "it's kind of gummy" camp..... never got a mirror finish on pipe or 1018 without grinding. You must have that thing spinning fit to take off.
                        1000-1250 rpm, 3/4 BIP made in korea (from Home depot!). it does not turn like 1018... way way better. I don't know if all BI pipe is like this, but what I have in my shop is.
                        Last edited by lakeside53; 09-26-2014, 01:18 AM.

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                        • #13
                          Pipe is not round- true. But by machining a press-fit disc with a bored center hole, you'll get it averaged to a central point about as well as can be. If you don't use too much pressure, the pipe won't distort much, and your bored hole will be about as close to center as you'll get. Machine a stub to fit the bored hole and hold that in the tailstock however suits- a chuck would be fine. It may or may not be inline with the lathe axis, but it won't matter much. Machine the OD just until all the original surface has been cleaned away.

                          When you reverse the pipe and use the same disc, that end will center pretty much exactly like the other end did. Machine the OD there. If you want to be critical, reverse the pipe once more and recut the OD. The spindle chuck will be holding onto a machined OD at this point, and the pipe will be as wobble-free as you'll get it. Once you'd done machining the first OD again, remove the disc and turn the spindle slowly. Whatever wobble you see, tap on the 'high' side of the pipe until it turns wobble-free. At this point set up your steady rest and machine the ID.

                          Loosen only the upper steady rest arm and reverse the pipe, machine the other ID. Those bores are now going to be about as inline as you'll get. The shaft that is supported in the bearings may not be totally centered within the pipe, but it will be centered to the machined OD portions. If the OD of the whole length of pipe needs to be centered, then you'll have to machine it. But I doubt that will matter. If pipe is the chosen starting material, you will have done the best that can be done with it.
                          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                          • #14
                            Don't know this might really "solve" your problem, my "solution" was to start far away from size i.e. pipe that was far thicker wall and larger than needed OD enough so that I knew several boring and external passes could both be made before getting close to size. I guess effectively I was putting the tube shape I needed within the walls of the material I had so that even if out of align it still fit.
                            It then became a matter of getting an interior and exterior surface machined by repeated flipping of the part (could not machine any surface fully due to holding material), using one then the other surface as "true", two external and two boring passes and it was within reason (I was working towards the "spindle" of a welding positioner, needing to maintain as large a bore as possible so no vital measurements and still fit the bearings on the exterior, the OD important as to fit).

                            IMO the suggestion about establishing a running surface for a steady rest and the working from there is what should be done, I just did not think about it (if I am thinking about it correctly, at the very least it would add accuracy to the method you describe by allowing the interior plug to be fit more exactly re: alignment to axis)

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                            • #15
                              Originally posted by loose nut View Post
                              DOM tube is out, it is a project for a friend and he gave me pipe.
                              Well! If he had given you a tree stump would you try to use that? :-) In some cases the "offered"
                              or "supplied" material just isn't suitable. :-)
                              ...lew...

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