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mother of invention

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  • mother of invention

    Well, as the saying goes, I had to invent a way to hold a workpiece for a particular machining operation. I needed to bore the inner diameter of a tube that was too long for the lathe, and to machine the end of it square. I looked at the lathe and it was too short for this job, and too small of a spindle through hole as well. I looked at the mill and there wasn't a way to mount the tube to do the desired operation. Or was there? I ended up drilling a hole in some mdf for a close fit for the tube, then clamped the mdf to the table, with the hole over the side of the table. With the tube pushed into the hole, and most of the tube hanging straight downwards between the legs of the stand, I could now rotate the head on this ROUND COLUMN mill so that the endmill could be directed down into the open end of the tube. After positioning the x and y to bring the endmill close to the inner wall of the tube, using a level I made the tube vertical and clamped a couple of guide blocks to the stand to keep it that way. I also clamped a block to proper height to support the lower end of the tube. With the cutter set to depth, I slowly advanced the y axis until the cutter started cutting. I held the tube from rotating by hand while doing this, then rotated it by hand to machine the inner circumference. A few repeat adjustments of the y axis, and some checking the tube for vertical, and I was able to 'bore' enough out for a press fit of a bearing.
    Obviously, in order to be able to use the mill this way, the quill has to be positionable so it can look straight downwards towards the floor, without the table, the base, or the stand getting in the way. On my stand, I have about 40 inches between floor and the top surface of the table, so that means I would be able to 'mount' that long of a tube vertically. Turning it by hand against the cutter isn't something I'm going to recommend, but it worked for me, and wasn't hard to do. I got a pretty good finish on the bore, not great, but good enough in this application, and I got the bore quite much rounder than it started out. Milling the end of the tube square this way was a snap, still rotating the tube by hand, and against the cutter rotation. I can just imagine what would happen if I tried rotating the tube the opposite way, which would be giving the equivalent of climb milling. It would probably have generated some excitement to say the least.
    I've used this 'hang it off the side of the table' method before for making a blind slot in the end of a long workpiece, and for drilling the ends of long pieces.
    Anybody have any other clever mounting setups?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Darryl...That's one thing they have to give to our round column mills! I had a customer bring in a long shaft that needed a 3/4" hole drilled in the end. It didn't have to be perfect and he was in a hurry. I have a crude homemade V block made from angle iron. Tacked this to the shaft and clamped it to the base frame on the mill. Trued it up as best we could with a level. Spun the head around and drilled the hole.
    I have tools I don't even know I own...


    • #3
      Not exactly a set up but I was making some trays to rack mount a bunch of computers. It was a tight fit as the computer was 17" wide (tall) and the rack has an 18" opening. With 1" for the slides, that didn't leave any extra for things like screw heads. I had intended to countersink the holes for mounting the slides before bending the trays. I even had the drill press set up with the CS for the exact depth. But they were rushing me and I forgot.

      I tried it with a pan head screw and no go. So I had to countersink. Six of the eitht holes were no problem as there was clearance for a hand drill inside the tray. But two were about 1/4" from the bottom and no drill would fit. The trays were aluminum and the problem holes were next to the open front.

      What I did was make a 36" long countersink. Hand ground a conical tip on a 3/8" CRS rod and then cut four "flutes" with the Dremel. Had to relieve the edges carefully with the Dremel and a hand stone. Crude, real crude.

      Surprise! Surprise! It worked. The 3 foot countersink allowed me to reach the holes at about a 5 deg. angle from square and the screws fit perfectly. Shows you what you can do at 11PM on a Saturday.

      Paul A.
      Paul A.
      SE Texas

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


      • #4
        Thought I would add you can do it with a Bridgeport also. A place I worked at had a flat back chuck mounted on a large disk that allowd you to get the spindle bore past the table. Or you could use a large V-block or an angle plate with a fence and C-clamps.

        I find this angle plate very handy.

        Setting up can be the hardest part of a job so keep the tips coming.
        Jon Bohlander
        My PM Blog


        • #5
          That looks like a handy angle plate. Must be nearly time to visit a tool store again.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-