Newby trying to figure out best clamping method. 3" Tubing onto bridgeport table - Page 2
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  1. #21
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    Quote Originally Posted by Goerger View Post
    Yes. We have a really nice belt sander at work. Im going to pin the work and swing it to meet the radius spec.
    I placed an order just now through msc for a ream, a set of v blocks, a 1.5" 4"LOC 2 flute end mill and an r8 holder for its 1.25" shank.
    In the meantime im going to continue considering clamping methods but i feel confident that this is going to be successful.
    Im not too experienced using my mill with high accuracy and finish in mind. I have the older step pulley head. Would you, or anyone else give me cutting advice such as rpm, should i rough some out with one of my many used cutters saving life on the one new one? How much material should i attempt to remove on the first / subsequent passes?
    You fellas are awesome, so happy i joined this forum.
    That will almost certainly be exciting! Tube likes to flex and move. Big cutters like to suck the edges of tube in and that's too much cutter for a bridgeport. When I do stuff that's to big, I prefer to make a lot of downward strokes so that I'm only removing material in a tiny area. I think you will not possibly take the whole width with the side of the cutter. Best of luck.

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    I like kopal http://www.kopal.eu/download/Kopal_c...l_clamp_42.pdf, I don't like the price though, but you can use the chain idea with other way of tensioning.

  3. #23
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    An 1.5" 2 flute EM will grab that tube quicker than an OH..Sh.. First drill the 3/4 through hole, this provides a way to move the work into position after one of the other tools tosses the work somewhere. After the 3/4 holes are made, turn the work 90 degrees and using a 5/8 BE mill, hog off those areas that lead to the radius that you intended to use that 1.5 EM on. If your EM is BE mill now carefully feed and cut that radius. If square ended, you could turn the work back the 90, and use that monster as a drill, taking small bites. For me I would use a boring head set to the radius needed.

    That work needs real holding, how about putting a shaft through the 3/4 holes, with hold down on each side, when horizontal, and a bolt into a tee nut when vertical.

  4. #24
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    Don't rely on a hole saw to cut an accurate hole in your wooden v-blocks. They usually cut WAY oversize. Use an undersized hole saw and sand the wood to the proper contour.

    Plunge cut the internal radii. Take small bites. The cutter and holder stick out a long ways. Lots of leverage to move the head of the BP. I probably would have finished those radii using a boring head, which I assume is not available to you. When you do the straight cuts from the radii to the ends do the to and bottom edges separately. Use plenty of kerosene or WD40 during the cuts.

    For the end radii make up a couple 1 1/2" dia. bushings to fit the bolt. Use them as guides when grinding the end radii.

  5. #25
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    Copes on round tube are ALWAYS perpendicular to wall u.n.o. Cuts are perpendicular or parallel to miter. other than the 7/16 holes for 3/8 bolts (with wth tolerances?) a mill would not be my first choice of tools. You would need rotary, not index, to maintain square to wall edge. roughing it out with teeth, grinder, skill saw, rotozip, cordless router with vee base (very handy ghetto fab steady die grinder for round stuff) and then sand/file till you hit your lines. A good few copies of your paper template, with holes to match thru holes for positioning of course. A belt sander wont fit most of the cope either.

    addendum edit part:

    your drawing fails the requirements for thickness of material to hole (1xthickness between bolt hole and inside edge). It is a common mistake when people draw round stuff and fail to compensate for curve.thingy.jpg .170 < .25 . you can cheat some with chamfer tricks, well within eye trick realm, but you are not going to cheat material strength.

    later... much later, a close but rough outside wrap for perpendicular cuts, of course I haven't checked it, and I did add some material selectively to give you material for chamfer and still hit .25 wall clearance.untitled-2-converted-.jpg .
    Attached Thumbnails Attached Thumbnails untitled-2-converted-.jpg  
    Last edited by memphisjed; 09-20-2019 at 05:44 AM.


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