Why is my lid jig a miserable failure?

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Bolster
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Why is my lid jig a miserable failure?

Post by Bolster » Mon Nov 18, 2013 6:15 pm

I want to make a lightweight lid of aluminum flashing (.010 thickness) for an aluminum mug (an Imusa mug which is 3.9" ID). I'd like to take the mug and lid backpacking, and be able to boil a bit of water in the mug for rehydrating meals. The lid is the sort that sits down into the mug about a quarter inch, then toward the edge bends vertically up, and then bends back to horizontal at the edge, to sit on the rim of the mug. Here's a photo of someone else's lid--perfect, exactly what I want to make. (If I can't make one myself I may have to buy one from this guy, who apparently possesses an IQ about quadruple of mine.)

Image

I thought about how I might bend the desired ledge into a circle of aluminum flashing, with the tools I have, and came up with the idea of (left to right in photo) a "fulcrum" with pivot screw for holding the lid at its center, allowing it to rotate; and an "anvil" and "presser foot" which would bend the edge into shape. The orientation of the lid is upside down during fabrication, and the mill is turned off--nothing is spinning here(!), except for the lid blank, which I turn by hand on the pivot screw as I work around the edge.

Image

The anvil is radiused (along the Y axis, you can see it) a little under the dimension I need, at 1.75 in. The presser foot does not have a similar radius (a problem?), I left it square, as you can see. I use the quill of my mill to move the presser foot up and down (Z axis), gently, while slowly rotating the blank. There is a horizontal (X axis) space between the hammer and anvil of about .1 inch, which I've been keeping wide, in hopes it will allow gentler bending.

Regarding the sharpness of the working edges themselves (both anvil and presser foot) they are only slightly filed.

Result: Miserable failure!

Image

Even when I try to gently massage the desired rim onto the blank, I get all kinds of problems. First thing is that the blank starts to warp or bow, popping into different non-flat curves as I go around. If I keep up the work, I start to get wrinkles at the lip. And if I forge onward, I eventually open up a circular rip in the lid, like a can opener would do.

Clearly I'm doing at least one, and possibly, several things wrong. I think I am stretching the metal so there is "more of it" around the rim, which must be causing the warping and bowing. I'm considering radiusing the presser foot to see if that might help. I think there'd be less metal stretching, as I can see the square edges of the presser foot making imprints around the lid as I work.

Very frustrating, after taking the time to make the jig, to have such an unpleasant result. Help appreciated.
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ctwo
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Re: Why is my lid jig a miserable failure?

Post by ctwo » Mon Nov 18, 2013 9:00 pm

you need to take very small bends over and over. Look up metal spinning on youtube for some though provoking demonstrations...
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Bolster
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Re: Why is my lid jig a miserable failure?

Post by Bolster » Mon Nov 18, 2013 9:05 pm

Thanks--I should have specified the speed at which I was working. Going around in a circle, I'd take maybe 20 very small presses (the slightest bend appears), then the next rotation, 20 more (a little more bend), each time pressing only the amount that the metal seemed willing to give. I think I gave up after maybe 15 rotations (15x20 = 300 small presses). I thought I was working at an agonizingly slow pace. Maybe not slow enough?

I'm vaguely familiar with metal spinning but don't have a lathe. You think it can be done on a mill? Is it a better process than what I'm trying, do you think?
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Re: Why is my lid jig a miserable failure?

Post by Harold_V » Mon Nov 18, 2013 10:13 pm

I am not a die maker, nor have I worked in that capacity, in spite of my many years in the shop.

Doing it progressively, in steps, isn't likely to work well, as the metal has to stretch properly, otherwise you'll get the distortion you're experiencing.
If you're enjoying playing with this project, try turning a male and female die, then press the piece in one operation. You may have to apply modest pressure to the starting material, so it is controlled as the depression forms. It would have to be able to be pulled without allowing puckers.

If I had experience, I'd know exactly how to go about this project. Perhaps one of the die makers who frequent the board will provide better guidance, and set me straight.

Alternately, you could easily spin the profile (as ctwo suggested), using your metal lathe, spinning against a wooden form. I've done that with acceptable results. Use a live center against an aluminum plate, holding the material against the form. Use some stick wax for the spinning process. Place a piece of hardwood in your tool post and use it to cause the aluminum to form against the pattern you make, which would represent the inside of the lid and the flange area. Once formed, you can trim the piece to the desired diameter. Run the spindle at a modest speed. I expect that if you work from the center, out, you should enjoy success.

Harold
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Re: Why is my lid jig a miserable failure?

Post by mechanicalmagic » Mon Nov 18, 2013 10:22 pm

A few thoughts, probably all wrong.

1. Aluminum for flashing is probably already hard tempered, just from the rolling process. You might try to anneal the stock, then temper after forming.

2. The only time I have had much luck with 3D curved surfaces was to press a rubber plug into the aluminum, while the Al was on a die. In this case I would think a wood female die might be enough.
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Re: Why is my lid jig a miserable failure?

Post by Grantham » Mon Nov 18, 2013 10:55 pm

This is probably blasphemy to us guys who enjoy building stuff. You may find it's one of those things where it's easier, cheaper, faster, etc. to just buy an aluminum mess kit. $10 buys a nice little kit.

Aluminum flashing is not suitable for forming. I tried annealing it in my heat controlled oven and it melted before getting to temperature. The coating also stinks to high heaven when heated. For metal spinning, 1100-0 aluminum seems to be the only thing that works reliably for me. You can see it in my metal spinning video. But, back to my first comment, the cost of a sheet of 1100-0 costs more than a camping kit.

Rod

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Bolster
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Re: Why is my lid jig a miserable failure?

Post by Bolster » Mon Nov 18, 2013 11:37 pm

Thanks, guys.

My jig sounds like a dead-end project. I should have checked with you guys before starting, and saved the fabrication time. So now, I guess I chalk this up to "practice."

Interesting about the flashing being too hard to work--I had not thought about that. I'd been using flashing to make windscreens with good success, but that's a much simpler task with no forming required.

I think I'll cut up a beer can and see what happens when I use a softer metal. Perhaps something other than flashing will give me a shot at this.

I'm also going to radius the presser foot (along the Y axis, that is), so that there is a relatively small area where the bend is actually occurring; that *might* reduce stretching somewhat. As I mentioned, I can see the corners of the non-radiused presser foot contacting the flashing and poking little dimples in it. (None of this happened, mind you, when I visualized this in my head!!)

And, Grantham, you are correct; someone called "smokeeater" has made a big heavy press-die to make Imusa mug lids and will sell me a lid for $7. (Never mind that the mug itself costs $2.) But you know how these things go...sometimes you get a bee in your bonnet and say, "Heck, I could make that myself..."

Ha! "Too soon old, too late smart."

If interested, see Smokeeater's video, around 7:00

http://www.youtube.com/watch?v=kv5RDx7D1pA
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steamin10
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Re: Why is my lid jig a miserable failure?

Post by steamin10 » Tue Nov 19, 2013 12:41 am

I agree that flashing material will be wrong because of its hardness, and tendancy to crack, in the normal thickness.

I have had some success forming an 1/8 disc into a dome with a bearing mounted to shove into the blank, on a wooden form. Stability is a problem, but it can work fairly well.

Cans and most thinly formed aluminum objects are progressive die forming, which is another ball of wax. Round blank, drawn to a cup, drawn to a shell, drawn to a can blank. Its amazing. The machine I saw ran 4 abreast, at about 20 strokes per minute. I have no doubt things have changed since.
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Re: Why is my lid jig a miserable failure?

Post by ronm » Tue Nov 19, 2013 9:19 am

How about making a female & a male die from 2" steel plate, laying the material between them, & smacking the male w/a 12-lb. sledge? I have no idea if that would work, & it's for sure not cost-effective, but it sounds like fun...maybe I just like to smack things w/a big hammer... :twisted:

Or maybe I've just had too much coffee this morning? :roll:

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Re: Why is my lid jig a miserable failure?

Post by tornitore45 » Wed Oct 15, 2014 8:30 am

From an old post from Dave, bless his soul.
1. Aluminum for flashing is probably already hard tempered, just from the rolling process. You might try to anneal the stock, then temper after forming.
How do you temper aluminum? And what happens to the metal?

As an aside...

Temper is a ambiguous term. In English it means to reduce the hardening following a heat/quench cycle by reheating to a lower temperature. It also means a short fuse.

In my mother language we take a short cut and Tempered Steel means "hardened and tempered" since there is no point in tempering unless previously hardened.
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Re: Why is my lid jig a miserable failure?

Post by Harold_V » Wed Oct 15, 2014 3:14 pm

tornitore45 wrote:How do you temper aluminum? And what happens to the metal?
Heat treatment occurs first by solution annealing, whereby the alloy is heated near the melting point, then quickly quenched. It is then given heat treatment at a specific temperature (artificial aging). Depending on the alloy, some will harden simply by aging.

Hardness occurs by grain growth. Not all aluminum alloys can be heat treated, and those that are capable can undergo various processes to achieve the end goal.

I am not well versed on the subject, but having machined weldments of 6061 in both the annealed and heat treated conditions, I can assure you, there's a world of difference.

Harold
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Re: Why is my lid jig a miserable failure?

Post by warmstrong1955 » Wed Oct 15, 2014 5:33 pm

Hardening & annealing 6061 is pretty simple.

Back from old motocross days, we used to do a lot of straightening of many things, including clutch & brake levers. After a straighten or two, any bending would cause them to work harden, they would break when you tried to tweak 'em back into shape.

No problem. It was easy enough to grind a vee in the broken ends, and heliarc 'em back together. If you let the lever cool off in the air after welding, it was then sometimes too easy to bend. Quench it in water, and it was much like a new one. I used to weld mine, and give 'em some squirts with water from an old Windex bottle immediatly after. Had to find that happy medium of hardness.

I would think that aluminum sheet, no doubt depending on the alloy, could be annealed with some patience, and a propane torch, and left to air cool....which wouldn't take long.

Bill
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