Newby trying to figure out best clamping method. 3" Tubing onto bridgeport table
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    Default Newby trying to figure out best clamping method. 3" Tubing onto bridgeport table

    Im a sheetmetal guy but the army thinks im a machinist. I agreed to use my newly purchased bridgeport to mill some aluminum tubing that will be used as spreader bars for rigging helicopters or components inside of cargo jets. The ends of the 3" aluminum tube get holes and relief to make way for the chains. I dont own an incredible amount of tooling and this project has a deadline. I would very much appreciate advice for clamping to my table and an appropriate cutter. Its 1/4 wall 6061 al.

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    Plasma cutter with a template....Well, it would get the job done eh ?

    Do you have a couple of "Vee" blocks handy ? see if you can set them up on the bridgy table, strap clamp on top to hold the tube into the Vee blocks.

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    Quote Originally Posted by Goerger View Post
    Im a sheetmetal guy but the army thinks im a machinist. I agreed to use my newly purchased bridgeport to mill some aluminum tubing that will be used as spreader bars for rigging helicopters or components inside of cargo jets. The ends of the 3" aluminum tube get holes and relief to make way for the chains. I dont own an incredible amount of tooling and this project has a deadline. I would very much appreciate advice for clamping to my table and an appropriate cutter. Its 1/4 wall 6061 al.
    .
    .
    often just clamp 2 pieces of wood with .020" shim between and hole saw a 3" hole through them. when the 1/2 round wood pieces are clamped down to table with tubing in them, with hold down clamps since they are round shape they will not distort tubing as much as the hold down clamps alone. you could use aluminum pieces too but if tolerances not critical, wood will often work as soft jaws like a soft collet to less likely leave a mark on part being clamped

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    Lay the tube along a t slot. clamp the bottom of tube bore to table. for good result both ends need to get clamped

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    Quote Originally Posted by Bluejeep View Post
    Lay the tube along a t slot. clamp the bottom of tube bore to table. for good result both ends need to get clamped

    This was the quickest, dirtiest, simplest way that occurred to me, too.

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    Quote Originally Posted by Bluejeep View Post
    Lay the tube along a t slot. clamp the bottom of tube bore to table. for good result both ends need to get clamped
    That's always worked for me tip, if you have to clamp across the top of the tube, turn up a wood or plastic plug that's a sliding fit in the bore for the clamp to bear down on.

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    Quote Originally Posted by Bluejeep View Post
    Lay the tube along a t slot. clamp the bottom of tube bore to table. for good result both ends need to get clamped
    Unless you need that hole saw to "go all the way"....

    YouTube

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    Hardwood responds to quicky needs - holder up here was duplicated other end. Easy to rig the usual strap downs as needed
    Attached Thumbnails Attached Thumbnails 03.jpg  

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    Is this round tubing or square?

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    Having some difficulty uploading images. Sorry for confusion. Its 3" round.
    Tonight i drilled a 3" hole a little off the side of a piece of pine 2x4. The work is laying in a t slot and fairly cinched down with a clamp stack on both sided of the 2x4 (trying to equalize the squeeze.)
    The army needs 10 of these and only provided me 10 pieces cut to finished length. If my pictures dont load, i think i will duplicate my clamping for the tail end and send it. I do not have an appropriate cutter though. I found a 1.5" 2 flute hss in an extended length but it requires a 1.25" r8 holder. MSC has these imported. Do you suppose this is a good combination choice?20190918_223904.jpg20190912_105357.jpg

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    For a quick job I would buy a hole saw and mandrel from Hoe Depot or the like. Make your clamp from a 2x6 or two 2x4's on edge with the hole drilled through. Drill a small hole at each end top to bottom and spaced so you can run a clamp stud up from the table and put a nut and washer on the top.
    Bil lD.

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    20190918_223750.jpg
    Hoping you can see my method. Think it will work? 1 chance to get it right 10 times.

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    Looking good Houston

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    Set-up loose fine/Ok ..but a mill deserves a set of V blocks to make such jobs a snap.

    Your set up could have a table end stop so one measure will do all parts.

    Good to have a set of 4 v blocks even if you have to make them out of hard wood. Some times you have to get such a job off the table for facing ends or the like.
    Last edited by michiganbuck; 09-19-2019 at 09:45 AM.

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    What's your plan for the radius? And for indexing 180°?

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    Quote Originally Posted by TeachMePlease View Post
    What's your plan for the radius? And for indexing 180°?
    Shouldn't need to index. Since he's clamping to the T-slot, he should be able to go thru on that hole. Based on the width of the T-slots, the fact that he's looking at extended length endmills, and that center feature, he's gonna be butthole-clenching close to the table if he wants to take both sides off at once. Might just leave himself a big burr to take off, but it should theoretically be doable.

    Still leaves the question of rounding off the square corners that this is going to leave behind?

    Edit for clarity

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    I'm sure you can make serviceable safe parts. That said, you'll not be able to make them to print. +/- .0005 tolerance on a clearance hole for a bolt... WTF?

    I would use a 2.25" hole saw or annular cutter.

    I think the print is misleading shitty hand drawn representation of the profile left by intersecting a 3" tube with a 2.25 hole saw. What looks like a pair of radius at the bottom of the top view is really just the result of a round 2.25" diameter cut from the side. But then they up round off the ear around the bolt hole at a .75 radius.

    I don't see how your going to follow that .75 external radius without swinging the tube 180 or a cnc unless you nibble it away like an ethc-a-sketch.
    the ends of the cuts also call for a .1 full radius everywhere which follows the cut around and this is impossible to mill without 5 axis. Obviously you'll be sanding or filing those by eye.

    If you want the swing a .75 radius without cnc or nibbling, put a pin sticking up from the table and physically walk the long end of the tube around it slowly.

    I would probably make a card paper template and draw a radius with a sharpie and belt-sand them.

    tube1.jpgtube2.jpg

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    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.

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    I did not see anything in the photo but the far end needs to be held up by something so it does not tip down. It will not need the full clamp setup at the far end assuming you do one end at a time.
    Bill D

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    The two points of advice I can give are this:

    1. Don't get greedy. It will seem to take forever to remove the material .030 at a time, but just remind yourself that you are holding all this down with a 2x4. As soon as you feel the setup shift on a heavy cut, you will be kicking yourself pretty damn hard, since it would be near impossible to make the hole to spec after milling. Maybe you'd be able to realign the hole with a pin for the milled features, but that's a can of worms for sure.

    2. Leave a bit of meat on for your finishing pass. Don't try to sneak up on it .003-.005 at a time. When you get close, divide your last .040~.060 into three equal cuts, measuring in between to make sure the cuts happening are as advertised on the dial.

    Good luck!

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