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flycutting a taper

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  • flycutting a taper

    Today I needed to taper the bottom side of a piece of angle iron. It had to go from 1/4 inch thick to 1/8 thick across a span of 1-1/2 inches of the width. I figured to hold it in the vise, with some wire or something laying in the bottom so it would cock sideways a bit, then a similar thickness of wire at the top of the other jaw so it would close up evenly and tightly on the angle iron. Might have worked, but then I realized that the other side of the angle had been cut down to less than an inch, leaving basically nothing to work with in the vise. I thought to maybe grip it across the width, with one edge high- maybe set it up on different parallels to give it the angle I needed- but then it would just pop out of the jaws, probably taking out the flycutter and handing me a bad evening. Then I thought of the angle vise. I could clamp it in that and set a slight angle- could have worked I suppose, but again I didn't think it would remain in place very well. The angle is 3x3x1/4 and 5 ft long- the taper needed to be about 17 inches long from one end, and as I said about 1-1/2 wide, bringing the edge down to 1/8 at the thinnest.

    In hindsight, the angle vise would have worked had I not already cut most of one edge off the angle iron. Then I remembered the custom angle mounting jig I had made to machine some dovetails. I set it up on the mill, with the angle I needed, then used a pair of C clamps to hold the workpiece to it. The taper was flycut between clamps, then the workpiece moved along and reclamped, flycut, etc. The job got done and it doesn't look too bad either, though that doesn't matter since it won't be seen. This thing is a custom fence that you can raise and lower, and it rotates backwards as you lower it- thus the need for the bottom taper so it can sit flat against the other part that I can't move.

    My drum sander sits about 4 ft away from the center of the mill, so I was able to rig up a support on it for the long end of the angle iron to rest on. A universal support of some kind would sure be an asset in the shop- I'll have to get or make something useful like that.

    Anyway, I got the job done. How would anyone else have done this?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Could you tip the head on the mill?



    • #3
      I would have placed a rod along the slot of the mill. Balance the angle on top of that. Set a V block upside down on the top of the angle iron. This should present a flat surface that can be easily clamped parallel to the mill's tale.

      Oh, shim the rod to the required angle.

      As an alternative, place the piece sideways in the vice, with the V towards the jaw. Put a 2x1 rectangular piece against the other jar as a spacer. You will want to support the end with 246 blocks or something to prevent deflection as you cut.

      Pictures would have been nice.

      At the end of the project, there is a profound difference between spare parts and extra parts.