Shrinking a large panel

[Bart]

Another question on shrinking this panel, its quite a large panel, im tempted to make it in 2 halves but this time i would to make it one piece. (Try )
I made these shrinking dies for my pullmax but seems to fatigue the metal and split it.
Any ideas on the shrinking dies and the amount of shrink on this panel?

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[Jaroslav]

Do you have the opportunity to shape it differently? I'm thinking of EW bulging the center and the edge lies down alone. Exactly to size.
I mean stretch in another place. Do not download.

[Bart]

Originally Posted by Jaroslav

Do you have the opportunity to shape it differently? I'm thinking of EW bulging the center and the edge lies down alone. Exactly to size.
I mean stretch in another place. Do not download.

I wheeled the center already. It doesn't have much curve. So it pretty well ok.
But the edges are lifted. I'm hesitant to use the shrinking dies I have because they have torn other sheets before.

[Bart]

I would like some advice how to improve my shrinking dies if possible?

[Bart]

I thought shrinking the edges would bring the sides down but I may have miss read the sheet. I could EW edges and bring it back to original I guess

[Jaroslav]

Bart. I think if you carefully enlarge the center in the EW, the edges will lie down on their own.

[Bart]

Originally Posted by Jaroslav

Bart. I think if you carefully enlarge the center in the EW, the edges will lie down on their own.

Thanks, ill try

[John Buchtenkirch]

Originally Posted by Bart

I would like some advice how to improve my shrinking dies if possible?

I could look at hundreds of photos of different thumbnail shrinking dies and not even be able to tell you if they shrink or not. The shrinking ability or lack of it is mostly determined by the “hit point” which shows up after running the dies in light contact with the blackest thinned drain oil between them. The “hit point” should be the Cheshire Cat’s smile swinging around slightly in front of the beginning of the thumbnail ramp for lack of any better way to describe it. Also consider if your dies close too tightly they will stretch the metal. The thumbnail should have extra clearance for 2 or 3 sheets to slide thru it. Also look at your metal after making one pass thru the dies, any dig marks in the metal should be read as being stretching and possibly an edge on your dies could be polished away to eliminate that problem. You can spend a bunch of time tuning / dressing shrink dies . GOOD luck ~ John Buchtenkirch

[Marc Bourget]

The successful thumbnails that I recall (full disclosure, no great experience here) have a longer, more gradual, transition along the length. IMHO a thumbnail is like an in-motion tuck point shrinking approach. You're trying to persuade the metal to shrink. If you have a short, rounded male, you run the risk of both stretching at the same time your shrinking and this may be the cause of your "fatigue and split" results.

[steve.murphy]

Also keep in mind that the fore and aft relationship between the top and bottom of the dies can also create stretching points if the clearance between the top and bottom dies when closed is too little.