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grinding a weld inside a pipe 8' from the

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  • grinding a weld inside a pipe 8' from the

    I need to butt weld 2 sections of steel tubing that are 8 feet long, 4" ID. The function of these tubes requires that the ID is ground smooth and flush at the circumferential weld. The welding process will generate and internal weld bead about 1/16" inside the tubing bore which I need to grind/finish.

    So here is the million dollar question: How would you grind the weld seam inside a 4" tube that is 8 feet from the opening.?

    The tubing is seamless DOM.

    Whatta think?


  • #2
    Piece o' cake. Just cut the tube off close to the weld, so you can get at it with conventional grinding tools, and weld it back together again when you've finished grinding. Ta-dam, finished!

    You do realize this might not be seriously intended..?


    • #3
      Is there any posabililty you could make a connector sleve and then do two lap welds after sliding the ends of the pipe into the connector sleve?


      • #4
        1) 4" opening is large enough that it's conceivable to make a customized pneumatically powered grinder jig with you can send down the 8 feet length. I have no doubt that such a machine have been built before for specialized applications.

        2) Machine a sleeve which will go over the two pipes. Using MIG, you may be able to weld the two outter seams without distorting the ID of the tubes.

        3) Machine a round copper bar who's OD is the same as the ID of the tube. Slip the copper in the tube where the butt joint will be and carefully MIG weld around the tube. The copper will minimize the bead information inside the tube. Knock the copper bar out once the welding is done.

        4) Electron beam welding may work but the 8 foot length may pose a problem



        • #5
          The scenario described seems very similar to one Guy Lautard presents in Machinist's Bedside Reader (either # 1 or #2), wherein he depicts a homebrewed scheme for boring out large cylinders. It had a kind of racheting fed cutter traversing back and forth thru the bore. I don't have that handy now, and can't recall exact details. So don't know how it might be adaptable to a grinding setup. I mention this mainly to possibly help stimulate other ideas from any familiar with Lautard's article. Of course 16 ft is a pretty long traverse!

          Tho Dr Rob's idea has merit I guess. After all, one could cut one of the pipes into 16 six inch pcs, weld on one piece, grind that bead, then weld on the next, grind, ...,weld, grind, ...etc. (joking of course)
          Lynn (Huntsville, AL)


          • #6
            Here's another possibility: There's a company called "Extrude Hone" and specialized in getting a smooth surface in areas not normally accessable to grinding tools. Their process involves a putty like substance with abrasive materials mixed in. They then squirt that through whatever needs to have a smooth surface under high pressure. (GM uses them to polish the air intakes for the Corvettes.) You could either get them to do the clean up for you, or figure out a way to do it yourself.


            • #7
              If you're not committed to the welding process that leaves the internal 1/16" bead you need to remove, you might consider laser welding. Lasers give an extraordinary control over heat and penetration. It's possible you could do the weld to your strength requirements without the internal bead. It's probably worth asking a shop in your area. Good Luck!


              • #8
                Great feedback ...thank you!

                The design of the workpiece is fixed. It is a high volume production piece. The scenario of 2 pieces welded together is economically the most feasible as well as meeting all of the design goals. I expect the cost savings of the butt joint/internal grind design to far surpass the cost to develope a technigue and tooling to make the parts.

                So for the fun of it, let's say that there is an unlimited budget to develop a process and tooling to grind the ID.



                • #9
                  Check with Ladish Tri-Clover, or other manufacturers of sanitary or dairy tubing products. They do this regularly, heli-arc with purge, grind and polish.
                  I am thinking something like a cylinder hone on long shaft, but they may be able to supply the equipment or provide the assembly.
                  Jim H.


                  • #10
                    How about an air powered die grinder. Mount excentric in a sleve with acme thd on OD - sleve is in holder less than 4"OD - holder has 3 cam locks on OD that lock the holder in position and centers it. Moving the holder to the center of the pipe puts the grinding wheel in contact with the pipe just in front of the weld. The grinding wheel drag on the pipe ID and Weld causes the sleve to rotate moving forward on the acme thd. The grinder has a rotating coupling so as to not wind up the hose. May have to put a drag break on the sleve with the die grinder turning 8-10K

                    After I went through this I realilized every thing could be on the out side on the end of an 8' arm. That way the feed could be controled.


                    • #11
                      Good ideas all. What about using a cylinder hone on a long extention. Using a coarse stone and spray a coolant inside with a long tube


                      • #12
                        Rustybolt's reply is like several others, it misses the point. That is that "all" the cutting must be done on a single point, the weld bead. A hone cutts over a cylindical surface defined by the lenght of the stones on the hone. This is a good way to finnish up after the weld bead is cut out.

                        This bouncing back and forth is what I miss. I got down sized, right sized, out sized several months ago. Most of what I posted was ideas from all the previous posts in a different order. Keep it going and one of us will get it right.


                        • #13
                          I think Albert had the most logical and lowest cost solution - a machined copper plug. However, you may have to water cool it to be able to extract it in a reasonable time as the welding heat will expand it and you want a snug fit for a smooth bore.

                          This will allow full weld penetration, BTW. If the finish is critical then it could be bored out with a gunn drill.

                          The problem with that is the abrasive would affect the entire tube instead of just the weld. I was invited to their boot at IMTS to see their new micro-tech stuff (had a dance with a doctor instead). It is a neat process - Ultra-slow waterjet !

                          [This message has been edited by Thrud (edited 11-12-2002).]


                          • #14
                            Maybe you could use a cylinder ridge reamer with a long extension, and bring it down to where a hone could finish it off?


                            • #15
                              OK. What about something like a 16 ft wide pyramid roller with the cutter/grinding wheel sandwitched in the middle of the top roll.The top roll would be the high speed spindle and the lower rolls would be the low speed regulating rolls.

                              Rob. what are these some kind of long air cylider?