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  #51  
Old 09-04-2009, 09:00 PM
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tdoty tdoty is offline
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How about "the rearragement of the metal causes the tucks to form"? In reality, the surface area can change very, very little and still cause tucks to form. How much are you stretching the metal when using tucking forks? The surface area does not change until those tucks are hammered out.

As an example, would you say that a rubber mallet would do little to stretch a piece of metal? I would. Yet, I can work a piece of metal over the hollow of a stump with that rubber mallet and cause tucks to form. Very little, if any, stretching has taken place, yet the tucks have formed from the metal being rearranged.

You can stretch metal.

You can shrink metal.

You can cut and weld metal.

You can also significantly rearrange it without doing any of the above 3. Ruffling the edges of a panel can be done without significantly impacting the surface area. The perimeter area will become smaller, but the surface area is approximately the same (or, the same, depending on the methods used, the material and the care taken during the work).

Thumbnail shrinking is tuck shrinking, and, to my mind, the same as the rubber hammer over a hollow example I gave above. The metal is moved into a position that facilitates gathering it and allowing shrinking to occur, thereby making the metal thicker. Planishing those tucks out, after shrinking, will indeed cause some amount of stretch as you even out the metal thickness in the worked area.

Leaving heat out of it, the forms of shrinking we tend to use are methods of "stack shrinking". You basically stack the metal up to reduce its surface area. That happens on a molecular level, as you obviously do not want the pieces of the sheet to stack up (a major no-no when shrinking). Therefore, I think of stretching on the same level and not in broad, general terms.

Tim D.
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  #52  
Old 09-04-2009, 09:49 PM
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I had to try something.

I took a piece and just bent it over.This should be minimal stretching except for maybe the edges of the fold.

quill holder 146.jpg

quill holder 149.jpg

Then I straightened it out and it left a loose tuck.

quill holder 150-1.jpg

I hammered out the tuck,same results.
quill holder 152.jpg
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  #53  
Old 09-04-2009, 10:28 PM
Barry Barry is offline
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Quote:
Originally Posted by tdoty View Post
...Drawing as a side effect (or even an intention, I guess) is pulling in metal from an area outside what is being worked.

However, most processes we use to stretch metal will also draw in material from other areas of the panel. That drawing in of material is what causes the tucks to form. In general use, it may not be at all practical to stretch without the drawing in to occur, but it is that drawing in of material, not the stretch, that causes the tucks to form.Tim D.
Expounding on this, and bringing it back the the mention of the e-wheel and no drawing effect happening there, would it be fair to say that elastic stretching (Fay Butler's term I believe) will result in a drawing effect from the surrounding metal - ie hammering or applying force where the metal on the opposite side is not constrained (or not significantly constrained)?

Compressive stretching on the other hand (a die, anvil or dolly on the oppsite side of the force constrains the metal and doesn't allow movement of the metal out of the existing plane) won't have the drawing side effect....
The forces in the plane of the metal in the immediate area being worked are pushing outwards in compressive stretching - forcing the metal to rise up as a result.

With elastic stretching the "rising up"(as seen on the opposite side of the metal) is the primary effect, the drawing in from the outside is a result...


Man this business of putting coherent (to me anyways)thoughts into coherent language is tough stuff - no wonder we have wars
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  #54  
Old 09-04-2009, 10:33 PM
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Kerry Pinkerton Kerry Pinkerton is offline
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Metal flows to/from the path of least resistance....
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  #55  
Old 09-05-2009, 01:27 AM
Dyce Dyce is offline
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Thumbnail dies on the pullmax and the stump do a good job "trapping" the metal as the tuck is being hammered down.
Quote Barry
"With elastic stretching the "rising up"(as seen on the opposite side of the metal) is the primary effect, the drawing in from the outside is a result..."

Barry you are a deep thinker man! Any method you decide to use to shrink will be more effective if you have the drawing Barry and Tim talk about. The drawing is one way to "trap" the tuck. The tension you put in the panel stretching the center is pulling the metal together as you shrink around the stretch.

If you want to shrink to shape a panel you need to draw or pull the metal together. You need to pull the tuck and hold it, or the tuck just goes flat with no (or not much) shrink. I know hitting the end to is supposed to trap the tuck, but it's very limited. I remember Kirks shrinking fixture that trapped the tuck, and David Gardiner's video showed another way to "trap" the tuck. You could do this with the stump if you made a tuck with a tucking fork and crushed it in the stump.

Barry is right!!
"Man this business of putting coherent (to me anyways)thoughts into coherent language is tough stuff - no wonder we have wars"
That's my understanding of tuck shrinking.
Jeff


I use shrinking to make panels, just because shrinking speeds it up. I'm not afraid to stretch though. Just for the heck of it sometime take a micrometer and check the thickness of some of the panels you are reproducing. The factory pressing is nearly all stretch. I'm not concerned making a panel with stretch for this reason.

Last edited by Dyce; 09-05-2009 at 01:31 AM.
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  #56  
Old 09-05-2009, 04:13 AM
David Gardiner David Gardiner is offline
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Sorry to come back late - its that time zone thing again. For the record I enjoy a debate as well otherwise I would not be on here and I have enjoyed discussing this topic. Thanks Tim for your views and having read your last posts I see what you are saying but I think that Johnny has nailed it with his photos, the metal is deformed and you then have to dress the puckers out. stetching occures as well when the part is hit with the hammer/mallet to repeat myself this is kind of what happens to metal when it is drawn I imagine so forming in this way by hand is kind of like drawing in slow motion.

I dont have much time at the moment I will try to clarify the terms I mentioed earlier soon.
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  #57  
Old 09-05-2009, 09:50 AM
David Gardiner David Gardiner is offline
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Quote:
Originally Posted by jhnarial View Post
Your totally correct David.

It has been a interesting topic.
Thank you Johnny for saying so.

David
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  #58  
Old 09-05-2009, 09:55 AM
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Your welcome

I enjoy are discussions.It has even got me out to the shop a few times.

I believe the more we talk about it the more we discover.
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  #59  
Old 09-05-2009, 10:13 AM
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John Kelly John Kelly is offline
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(Snip)

Quote:
Originally Posted by Dyce View Post

If you want to shrink to shape a panel you need to draw or pull the metal together. You need to pull the tuck and hold it, or the tuck just goes flat with no (or not much) shrink. I know hitting the end to is supposed to trap the tuck, but it's very limited. I remember Kirks shrinking fixture that trapped the tuck, and David Gardiner's video showed another way to "trap" the tuck. You could do this with the stump if you made a tuck with a tucking fork and crushed it in the stump.
If you drive your hammer blows at an angle starting at the top outer edge of a tuck, you can trap it very easily without clamping. You are hammering against a strong buckle this way instead of straight down which will flatten the tuck if everything is not just right including the steepness of the tuck, and how hard you hit. Picture attached.

12.jpg

John www.ghiaspecialties.com
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  #60  
Old 09-05-2009, 12:26 PM
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Chris Bspoke Chris Bspoke is offline
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David ,
I didn't think that you or anyone else was getting mad , just looking at it from the view of someone new looking at this thread and it might of seemed like it was a heated debate. I think that this is a great disscusion going on just wish that i was in a position to add , i've been work with metal for about 15 years now but panel beating / metal shaping is a very new thing for me , I can say that this thread is very informing to me and i hope that it keep's going.

To all i think Johhny had a good idea with starting a new thread on the terms of metal shaping , Who's up for starting it so us newbee's can have a good understanding of the traditional terms and techniques.
Cheers Chris C
hope you all have a good weekend
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