Using a stretcher

I know this probably seems like simple stuff to most of you guys, but does anyone have any tips on how to use a sheet metal stretcher? I spent all day trying to make a curve and had every piece split. I used a light touch, but no matter how lightly i worked it there was a point where it would just bite in and snap, another cracked piece. I have never been so frustrated!!!! Any ideas would be much appreciated

 

Steel or Aluminum? What gauge? What part are you trying to make?

 

whos stretcher? HF, MB?

 

a picture is worth a thousand words.

 

Place stretcher on ground, Lay flat on back ontop of stretcher, Have nurse with big jugs administer medical attention !!! >>>>.

 

Its the set at school, so I have no idea what brand, but the set looked like this....

 

Shit, I didn't know I had an option!


Angel of Sin

Those look like lancasters.

What part are you trying to make? (what radius ???)

 

sounds like either you're working with a really thin guage metal or your working in too small of an increment while creating the bend. If you are stretching and are only pulling the metal along the the jaws after each stretch a super small amount that could be the problem..you'll get overlapping stretches

You could get thicker metal...or try sliding the metal through the jaws in slightly bigger increments while stretching. Also don't lay into the same spot over and over while trying to adjust your curve or it will split..that could be your problem too.

 

this is what we're making. 2 brackets one stretched the other shrunk. They're supposed to fit back-to-back when they're finished. I had no problems with the shrinker...

 

looks like too many pulls on the machine..and possibly some overlapping in the cracked areas ...you could get the same shape spacing the stretches a little further out

 

A lot of good questions have been asked and need an answer to give good advice. Assuming that you are using Lancaster style stretcher from HF the jaws have very aggressive teeth that mark the material very badly and set up stress risers. If you keep trying to stretch in the same spot the material will tear. To really help we need to know the type of material, gauge, and size of the section you are trying to stretch. As stated in an earlier post pictures would also help.

Stippled face dies that can be purchase from Gitzit will reduce the marking a lot and help with stretching.

 

Looks like you stayed full depth on every stroke. I start all the way in and work my way out a little. That die you are using must be very aggressive.

Another way to put the stretch in the outside edge would be with a Hammer and dolly(post dolly, steel table, anvil,ect.)

 

or just weld the crack up..ha

 

That could result in a cracked piece too though, couldn't it?

 

Didn't see your post with pictures. When you shrink or stretch you need to do this in a triangle shape. This means that the outside need to be worked more than the section next to the flange that is being bent by the shrinking or stretching. Your picture looks like you are going full depth with every stroke of the shrinker or stretcher. Make a pass going in about 1/3 the depth and then repeat it with another pass about 2/3 the depth. Finally a pass at full depth. Use light pressure it will help reduce the marking a little. Hope this helps.

 

### yee -- haw !!!! >>>>.

 

Is the material you are working with stainless? What gauge it looks very thin. Stainless is harder to work with because it will work harden very quickly.

 

Joe nailed it.

This is how I do it also.

 

Thanks guys. I have a much better picture of how to go about this tomorrow. Most of the variables are set by the instructors, but the technique is where I have been lacking. The working it like a triangle thing makes sense. I can totally visualize how that'd work. Thanks again, I can't wait to get back to the machines tomorrow