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Thread: How to form a flare on the end of Alum. Tube

  1. #1
    Whetstone is offline Aluminum
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    Default How to form a flare on the end of Alum. Tube

    I am working on a project where I want to form a slight flare on the end of a aluminum tube. I plan on using 1.125" x 4" solid stock (any recommendations on alloy?) and boring to 1", 3.875" deep. So I would end up with a 4" tube with a solid end with a 0.0625 wall. On the open end I would like to flare about 1/4" of the end out 10 degrees. What is the best way to form it? I would like to make 1-5 to start with the possibility of making a few hundred a year. I have a small (7 ton) knuckle press that I was thinking of using. What type of tool would I use? I think that I could turn a female from that held the tube ( small spring on the bottom to eject part). Drop in the turned aluminum part and have a 10 degree cone come down to form the end. Does this sound like it would work?

  2. #2
    Whetstone is offline Aluminum
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    This is what i am trying to form, a 10 degree flare about 1/4" long.
    Attached Thumbnails Attached Thumbnails imperosilca_medyellow_pump-2-1_001.jpg  

  3. #3
    Clews Machining is offline Aluminum
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    I use a die similar to what you're describing on stainless pipe and it works great. With the aluminum, you're going to have to use a formable alloy (i.e. not 6061-T6), but I don't see why it wouldn't work. With the wrong alloy, you're going to have cracking issues, but you should be able to work it out easily enough.

    Ethan

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    metlmunchr is offline Diamond
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    For decent drilling and boring you'll need to use at least 6061-T6. Anything softer will be like working bubble gum. But you'll need to anneal the end once the machining is done or it will crack when you try to flare it. 400* F for an hour or so will make it soft enough to flare with no problem.

    I think you'll need to make a sort of collet block to hold the tube. The problem if you just drop it into a hole and put it in compression is the likelihood of the entire tube swelling enough to lock itself into the hole.

    Probably the simplest and cheapest way to get there would be a 5C collet block and a 5C emergency (machinable) collet. Machine the female flare seat into the collet, clamp, insert a tool with the male flare machined on it, and give it a bump with a hammer. It won't take a lot of force to flare it, but you have to constrain the tube to make the flare occur where you want it.

    If you'd rather make something than buy the 5C stuff, you can bore a split block to grip the tube and dowel the 2 halves to maintain alignment. Clamp in a vise and use the male tool as described above to form the flare. On the male tool, in either case, its worthwhile to have a spud past the flare long enough to slide into the tube a bit to maintain alignment. No need for any super precision fit on it. Several thou clearance would be fine. All the spud does is align the tool so that you don't have to eyeball it to keep the flare concentric on the tube. We've got a set of 37* flare tools, commercially made, that work on this principle, and flaring 1" 16ga wall steel tube with them is no problem.

  5. #5
    Whetstone is offline Aluminum
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    Quote Originally Posted by metlmunchr View Post
    For decent drilling and boring you'll need to use at least 6061-T6. Anything softer will be like working bubble gum. But you'll need to anneal the end once the machining is done or it will crack when you try to flare it. 400* F for an hour or so will make it soft enough to flare with no problem.

    I would like to try this, as 6061 would be cheep and available. Is there a time frame after annealing where the metal will return to a hard state? would I be able to machine a few blanks, bake them, and form them a week or two later?

  6. #6
    Whetstone is offline Aluminum
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    I should clarify a little bit. For the female die I was planing on machining a block of steel 5.5" x 3" x 3" with a 1.125 x 5" hole borded in it (final size will be determined by spring). The extra one inch of length would hold a spring to eject the part after stamping. I imagined that the part would be fully supported bu the female die.

    I do like your idea of a lead in stud on the male die.

  7. #7
    nateman is offline Cast Iron
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    Looks like a dildo...

    my mind is in the gutter I guess...

  8. #8
    Ries's Avatar
    Ries is online now Diamond
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    looks like a bicycle pump to me, but I guess when my mind should have been in the gutter, I was working as a bike mechanic...
    adama likes this.

  9. #9
    metlmunchr is offline Diamond
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    Quote Originally Posted by Whetstone View Post
    I would like to try this, as 6061 would be cheep and available. Is there a time frame after annealing where the metal will return to a hard state? would I be able to machine a few blanks, bake them, and form them a week or two later?
    No it won't return to a harder state over time. For 6061, the T6 temper means the material has been aged at 350*F to achieve the hardness after solution heat treatment. What you'd do at 400*F is called over-aging, rather than annealling as I called it earlier. Once aluminum is over aged, the only way to recover the hardness is to start over with the solution heat treatment process. To be doubly sure you get the desired softening effect, you could bake the parts at 450*F rather than 400*.

    I should clarify a little bit. For the female die I was planing on machining a block of steel 5.5" x 3" x 3" with a 1.125 x 5" hole borded in it (final size will be determined by spring). The extra one inch of length would hold a spring to eject the part after stamping. I imagined that the part would be fully supported bu the female die.
    I'd think that will work as long as your spring is selected so that it can go solid without developing enough force to start the flare.

  10. #10
    wesg is offline Stainless
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    Form it in the lathe with a roller bearing on a bar. Or a live center if you've got a quick change toolpost and a morse taper holder.

  11. #11
    Philabuster's Avatar
    Philabuster is online now Titanium
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    Start with a larger dia bar and skip the forming operation. Just machine out the part complete. Done. Material costs are higher, but requires less labor and farting around.

    Second option would be to flare the part in the lathe at the same time you machine it (think spin forming), then part it off. I have done jobs like this and it works slick--especially when combined with a bar puller. Spin it fast and feed slow to reduce thrust load on Z axis.
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  12. #12
    ZAGNUT is offline Hot Rolled
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    i've got a long piece 6061-T6 tube, 20mmx1.2mm (same wall thickness that you want) that i use to open the skylights in the shop. within a week of using it the end was nicely flared out to an inch or more without any signs of cracking. there is also a part that i make that starts as 1" stock and gets the end flared to 1.125" while making the part in the lathe, wall thickness about 2.5mm. i just push it from the inside with a tool mounted on the cross slide. takes no real pressure to accomplish.

    so i say you should try flaring it that little bit without any annealing. might surprise you how easy it is. but i would try to do it with a gradual process like spinning rather that a quick whack.

  13. #13
    snowman is offline Diamond
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    I've got the clamping end of one of these if you want it ($20+shipping in hopefully a flat rate), I don't have a 1 1/8 die, but I've got smaller dies that could be ground out to your size, with your angle of flare.

    http://www.apsmetals.com/m50.htm

    Basically, the motor runs a live center on an eccentric, therefore you don't have the large amounts of friction of conventional flaring.

    Because you are forming each little tiny piece at a time, it's a gradual bend so you can get away with more. You may even be able to form the 6061 in it's unannealed state.

  14. #14
    Nmbmxer is offline Hot Rolled
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    I agree w/ forming it while still in the lathe. If you drill/bore it a touch over your flange length you can spin it out with a bearing while still having quite a bit of stickout from the chuck. After forming finish drilling/boring.

  15. #15
    behindpropellers is offline Stainless
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    Perfect part for hydroforming.

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