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There is no thing as directional dies either. The reason a flange seems to stretch long ways as you just said is that your die is covering the whole width of the steel. it is stretching side ways to the same amount. the flange will get wider too as it gets thinner.
use that same die in the middle of a sheet and see what happpens. It will just raise a buldge as would any shape die. hammer a 1 inch square piece of sheet metal. use a 1" long narrow hammer face. travel from one side to the other ot the piece. it will have grown in both directions the same. Now when you do the next inch in a flange it also grew the same in both directions but the combination of the two inches long vs. the 1 inch width it will now have grown longer then wider only because the piece isn't wide enough to grow the one direction. Also the real narrow longer die will stretch faster for it has less area in the hit. meaning it takes less force to smash the metal. A round die would do exactly the same thing on a flange but will take more force to do it for it is hitting in a bigger area.
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The Rod Doctor, Richard Crees |
#42
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[QUOTE=John Buchtenkirch;7738]OJ, now that you mentioned that you tig welded that roof I have a new theory, your weld bead was so proud in your first photo I thought / assumed you had mig welded it./QUOTE]
That was my first real attemp at doing this type of welding, when i went across the top i just welded the metal together and i could see that it was kinda 'undercut' and people on here have talked about the 'proud' so that i thought i was doing it wronmg on top and made it proud going around the corner. i broke my camera chip so i can't do a picture and yes since that experience i have been welding without filler metal, i just finished doing a door for a COE White that is much much better. As far as directional pounding goes, damn if i know if i am. I thought i was. I'll say that the metal is doing what i want - maybe not the first nor the second time i try something but i am persistant. I don't think i can really do anything 'wrong', i just might get some unexpected results that if i can repeat effectively i have learned something. As i said, i am having a ball. I try to read and learn, but i think i have gained more insight from this discussion than any other book or article. You two (Richard and John) are discussing the nature of 'how' the metal moves. Priceless. Thanks, oj |
#43
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!1s111.jpg !1s112.JPG !1s113.JPG !1s114.JPG !1s115.JPG |
#44
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[QUOTE=ojh;7761]
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You can always strike a piece of soft un-marred aluminum with your hammer to see what your hit point actually is. You can also reshape a hammer face on a belt sander to be a directional hit if you don't have one. Good luck. ~ John Buchtenkirch |
#45
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John,
I don't have enough time right now to explain again. But your last picture is perfect to do so. I will try to help you understand one more time. Tomarrow maybe. This is a subject that most don't understand. And therefore very hard to convince most.
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The Rod Doctor, Richard Crees |
#46
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Thanks Richard and John for not taking this personal. It isn't, I for one does not know what to think (yet).
But John, if you could do as Richard suggests in the revious post and run both dies over one sheet each. Cut exactly square cornered pieces and measure before and after to see which way the stretch goes. It would also be a good way to learn if there's more to it than the shape of the dies. Can a directional shrink be done by the path the die follows when hammering? When hammering a linear path with a round die each hit will escape easier in the direction of the previous hit because the sheet is already raised there? No, this is not a statement of fact, but a question. This is how I learned the little I know before coming to these forums. Make a test piece, does not work, clang in the bin. Do again a bit differently until it does work. Seeing is believing and I can see the sheet, but I cannot see the molecules moving.
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Akershus (Follo) Norway. Einar (at-sign) sjaavik (dot) no. |
#47
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This is a great subject. It probably should be in it's own thread.
Richard I remember that discussion on Metal Meet.I tried to find it this morning but had no luck. It is probably lost in a thread. I was in total agreement with you when I read it but now seeing the pictures that John just put up, I'm on the fence now. It sure looks like the directional dies are pulling the metal from side to side causing it to curve downward. I highly respect the both of you, so I am just enjoying the hell out of reading this. If anyone finds the link on Metal Meet please post the link. I would love to re-read it. This is what these forums are all about.
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Johnny Arial This forum is dedicated to Metal Shaping. Please stay on topic. |
#48
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I’m attaching a photo of a 1” strip I curved on my CP hammer maybe 10 years ago. I hung it on the wall to show potential customers directional stretching. I did it with a directional lower die that has the hit point tighter on one end and tapering off to looser other. I’m not saying that the strip is still exactly 1” wide to the thousandth of an inch but you can see the width is still very consistent. It’s an easy to see example of directional stretching that was done on one side of the strip with a directional die. If someone attempted to make the same piece with round (radial stretching) dies by hammering along one edge they would end up stretching the edge and loosing their consistent width of the strip. Hell, I made literally hundreds of stainless elliptical collars where one flange was directionally stretched with directional dies that had a tapering off hit point for the Osprey vertical take off plane. They were pretty thin (.027) stainless so I hammered them in stacks of four on the Pettingell. Tipped the lower die a bit by putting a shim under half of the anvil. Had a plywood template clamped on just below the anvil so I could check my stretching / curving progress constantly & quickly. Did so many that my dies started to develop a step from the edge of the part ! The second attached photo shows me with 50 or more pieces on my arms. ~ John Buchtenkirch !1ric2.JPG A res#17.jpg |
#49
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#50
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I use dies and hammers like John is talking about a TON and for the way I work, they are invaluable. Mine arent angled or anything, I remember discussions once on that, they are basically dead flad and I just feed progressivley from the edge of a panel to get it to do what I want it to do. Would a round die do the same thing? yes, but with 3x the amount of blows. i use a round die sometimes when I want to sneak up on something.
Marty
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