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Is there an easy way to square the ends of 4" pipe?

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  • Is there an easy way to square the ends of 4" pipe?

    I have a 24" length of 4" PVC pipe and I need to trim one end square to the sides to within +-0.003". I have a vertical mill but my largest end mill has 1" loc. It seems that laying it along the x-axis and rotating it would be the way to go but I haven't come up with an easy way. Anyone have any ideas that would take less than an hour. Any longer than that and it might be faster to do it by hand with a surface plate, angle plate, hi-spot paste and a file.

  • #2
    Hang it off the side of the table and turn the turret over to reach it.
    Then you can end mill it die maker style.

    --Doozer
    DZER

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    • #3
      make a couple of tri-angles that will go over the pipe and lock them in place with set screws.Set a stop up along one of the t-slots and place the tri angles against it. now you can mill the pipe and rotate it to mill all the way around the o.d.

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      • #4
        Sounds like that will only work in Bermuda.

        --Doozer
        DZER

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        • #5
          +/- 3 thou? A decent bandsaw...

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          • #6
            Turn up a split ring to clamp on the outside, put the ring up against the vise jaws with the pipe in the vise. Mill on the end sticking out of the vise, turn as required, keeping the ring against the vise each time.

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            • #7
              I think you could easily meet your accuracy target with a power miter box with a 12" blade.

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              • #8
                A big lathe and a steady rest.

                JL.................

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                • #9
                  You can make a disc to be a tight press fit inside the pipe, then tape a square of sheet metal to the center of the disc. A fixture on the mill has a rod extended that you bring the end of the pipe up to. The rod touches the sheet metal piece at the center of rotation for the pipe. Two verticals mounted on the mill table create a pair of corners where the pipe can be held into.

                  For that thin a pipe, and plastic, I'd be holding the pipe by hand and rotating it by hand against the rotation of an end mill. The rod keeps a central point within the pipe at a fixed point, and by rotating the pipe the endmill eats at the pipe until it begins to eat all around without having gap points. At that point, the end is as square to the pipe as it will ever be.

                  Note that you will have to test rotate the pipe to determine the point where the endmill will first begin cutting away material. Once you find this point, both hands will be free to roll the pipe while the cutter chews what it can, then you re-adjust and roll it again. Repeat til done.

                  Note that that kind of pipe is seldom round, usually being at least somewhat oval in shape. This method doesn't care about that- it will leave you a flat end as well as it being square. I would normally be positioning the table to put the endmill directly above the control rod. That's not essential, but it leaves the endmill the least amount of material to have in contact with the cutting edges at any one time, so the forces you need to apply to hold the pipe against the uprights is minimized. I've squared plastic pipe this way, but also have done some solid steel rods. If thought through, it's not a particularly dangerous operation, even though you're controlling the workpiece by hand.

                  I could do this process on one end of 4 inch pvc pipe about as quickly as it's taken me to describe the process.

                  Another way to do it is in a chop saw. You still need to create a corner somehow to nest the pipe into, which is formed by the base of the saw and a large enough upright attached to the fence. The same disc method can be used to ensure a proper positioning of the center point within the pipe. Screw something together to attach to the base to give you this reference point. To make the cut on the chop saw, you will have to hold the pipe with one hand, and chop a little, then rotate the pipe a bit, chop some more, repeat until a waste piece falls away from the end of the pipe. If you were really good with the chop saw, you could lower the blade into the pipe, then hold that position while turning the pipe bit by bit with the other hand.

                  Both of these methods require that you fix a reference point at the center within the pipe, which is what the disc does, then have a 'stop' of some kind to bring that up to. If your needs for accuracy can be met by jigsawing along a line around the circumference of the pipe, then another method can give you that accurate layout line.

                  A sheet of 11x14 paper is long enough to make one complete wrap plus some around the pipe. Wrap the paper, adjusting it til the one edge meets perfectly without the paper spiralling at all. If the paper is tight to the pipe, and the edges line up where they meet, that edge defines a line around the pipe that's square to the pipe. For me that's often the first step- jigsawing a jagged end off.
                  Last edited by darryl; 02-25-2010, 12:00 AM.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    I am with Joe Lee, the easiest way is with a lathe and a steady rest. Using a mill would be the hard way.
                    It's only ink and paper

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                    • #11
                      I agree with Carl and Joe. And if you don't have a steady rest big enough, make a pipe spider and use the tailstock to steady it.

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                      • #12
                        disc sander

                        I use my disc sander all the time for this type of work. Touch, roll, touch again, feeling while you go. If your sander table is flat and square I think you can hit square within .003"

                        I suppose you could clamp a fence on the table to help since it is a big piece to handle.

                        I keep a sacrificial vee block at the sander to help with small round parts.

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                        • #13
                          Do it this way with a fly cutter in the chuck.





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                          • #14
                            The lathe would be the best, but he only said he had a mill.

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                            • #15
                              PVC cuts so easily that you could probably get away with cutting with the side of a fly cutter. Either extend it from the quill far enough that you can reach the lower edge of the pipe without the quill hitting the top or set it to a large enough diameter that the quill clears the top of the pipe. The outside of some shell mills will work for this as well.

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