Struggling with metal shrinker/stretcher
 

Guys
I am trying to build new corners for the rain water channel for the inside of the trunk. See the yellow arrows in an example picture
https://i.imgur.com/PL3ljdL.jpg
This is a C or U Channel, but I am starting with an L. I figure i can always weld the wall on and covert the L to a C/U.
As another example image, I am trying to achieve this:
https://i.imgur.com/ZPKTha6l.jpg


When i shrink i start to get pretty good movement. But with only shrink on this side I can only get so far. This picture is in process so I am able to get more radius to the bend than what is shown, but not much more.
https://i.imgur.com/E9lhXqol.jpg

So last night i tried switching to the streching die and hitting the other side. Thinking that i have done all the shrinking i can. Maybe stretching will help push the metal more to form that "C" shaped radius (from a top view). Is this the correct approach?
https://i.imgur.com/bmW9ifpl.jpg

The problem i see is that when i stretch, instead of the metal following the contour that formed from shrinking, the side of metal being stretched fans outwards. Create a fan or sea shell shape.

I used a different piece of sheetmetal to help illustrate what the stretching die does.
https://i.imgur.com/vzCWPJql.jpg

I will watch some youtube videos to try and learn how to achieve the shape i need, but wanted to get some advice from those on here.

From my experience, that will happen. I generally finish the detailing on a sharp edged dolly to get the final shape.

Also, you have a lot of shrink going on. You may consider re-positioning the piece so that your die marks are not directly on top of one another. That could lead to cracking.

Todd, I suspect your steel is getting work hardened. Lancaster machines are pretty hard on the metal. It will work great and then just quits like you are seeing. You might try some heat, bend the angle around the radius you want, and hammer down the tucks that pop up.

Hi WC,
Kerry and I are seeing that your shrink is going well until:
1) your metal gets hard
and
2) your metal gets thick.

You can also shrink when the metal is hot. Heat until it is past purple/blue and goes "black" then shrink 2 or 3 times, and then spray the jaws with alcohol to cool them (no rust).
You will find you can get more shrinking for longer if you do this, and the metal will not crack ..... at least not for me.

One basic set of hardwood dies.

Attachment 44002

Hi,

In addition to the comments above, I have had good luck with making a pass thru the shrinker with the part at half depth of the die. Once you make a pass at half depth, tucks will form, go back full depth to flatten the tucks.

Bill

When trying to shrink or stretch two parallel flanges (the C shape you referred to) I tip the flanges over at about 45* and then perform the shrink or stretch (as needed) until you have the desired radius, then use your flat body hammer to take the flanges over to 90*. This process was used the other day when making the radius corners in our console folds..:

https://www.youtube.com/watch?v=1NdR3c_S8nE


I did some repairs on a Fairlane trunk opening similar to what you are tacking now. Part of this repair had the two folded part that needed shrinking on two opposite flanges. Did the same thing here, bend to 45*, shrink, then fold to the needed 90...:

Don't go to deep on the Shrinker or Stretcher. It will move more only working about 1/3rd of the flange.

Todd
here a simpler way to do that panel
step 1 cut enough metal ( by paper pattern)
Step 2 draw with compass the curve needed + height of Chanel width and lip make sure to have enough panel steel on the other side of you chanel
step 3 bend all the width of the Chanel (height,width and lip) down on the wheel by (kicking the lower anvil up on one side) follow the inside line of your curve (this get's done bit by bit) stretch the side as you go ...you can control the curvature as you go ...in another words......not enough stretching ...the panel will be too round,
step 4 once the panel is at right angle turn the next part (been the width ) back at level plain with the rest of the panel by using a pair of pliers or... back on the wheel, stretch some more in order to keep the now downwards part ( the height) at right angle, once that is done use a piece of steel the width of the Chanel about one inch long or less and simply turn the last piece back up parallel with the height, cut what you need on the top (remember...??????) You had enough panel steel prior to scribe the curve) .....and you will have your Chanel and no welds or shrinking and stretching with machines involved
Peter

I tried annealing the original piece and that helped a little. I did a little tune up on the Shrinker dies. Here is a new attempt. Still using scrap metal:
https://i.imgur.com/SMwJTxUl.jpg
I got better curvature this time. It wasn't as difficult. I just wanted a few youtube videos by LAzze and that got me going.

I tried to figure out a way to make the U Channel then shrink but that was impossible. I then bent an "S" shape and shrunk accordingly. I struggled with that quite a bit. I Might be able to make that work with a combination of Shrinking and Stretching but gave up.

Here is what i am thinking of trying. Shrink one piece to the desired curvature. Then weld a second piece to complete the U Shape
https://i.imgur.com/Yx4O50Kl.jpg

End up with something like this:
https://i.imgur.com/b8FzEt0l.jpg

No one will really see this piece so if it doesn't look great, i can live with that. I think...

What do you guys think? I don't have a bead roller right now. I've been considering it, but don't have alot of need for it nor the garage space.