Technical Tipping die versus brake?

I am shortening a hood that has a moderate contour. I've done similar things on smaller pieces with a tipping die then a shrinker to put back any lost contour. On a hood, I question if I can control the roller well enough to go straight even with extra hands. Obviously, using a brake will completely flatten the piece but that's probably fixable too.

The other difference is that the hood edge will be folded back onto itself whereas the smaller piece wasn't, it retained it's right angle flange. I've also thought, just do the fold on the brake and hammer into place then replace the contour curve by hand. Not sure that's even possible.

Ideas, helpful hints?? Thanks!

 

I had not thought of a hammer form... thanks... I did also wonder if the contour would mostly come back on it's own. I'm not leaving the 90 degree flange like I was on the smaller piece, its getting flopped right over in itself... (so to speak)... I suppose another argument to support the "coming back" theory is that the hood structure underneath is still all in place less the portion I've removed. That "should" help...

 

If you were to flatten the hood as you mention, I highly doubt the flange or hem would be in a straight line. Make a paper or tape flexible pattern on the hood, lay it flat and see if I am right or not. If it is straight, then a brake could do the job with the previously mentioned issue of getting the contour back.

If it's curved AND contoured like I suspect then some sort of hammer form or a tipping die seem like great options. What is your bead roller setup? I know some have provisions for adjustable stops and I have even seen dies that have a stop built into them for tipping a consistent flange.

At that point making your cut correctly is the big thing and your roller setup will just follow along.

Someone with more experience will have to chime in, but if you make a full hem it probably won't need the same amount of shrinking (or any?) that a flange would need.

Will a hem hold the shape well enough? Would a wire bead roll be an option for reinforcement?

 

I have probably the most rudimentary bead roller possible. It's a manual TDK model that's decades old and has no guide but I can picture how that would work with a nice smooth cut in the right place. Maybe I'll add some guides, that would be pretty cool...

 

Have a picture of the tool or the project?

We love pictures.

Look at what is available for dies for Mittler bros, Rexto, Roper, Lazze and other brand rotary machines and you might get an idea of how to modify your tooling to incorporate a stop.

I think once you get past 45-60 degrees or so on the right line it should follow pretty easily right?

 

Gonna be helpful to know what hood your working on

 

Folding the cut edge back against the hood on a relatively flat hood won't be too bad. My experience (and I'm a hack) has taught me that you can bend the metal to about a 120 degree bend with mechanical leverage pretty well, but that last of the gap has to be pressed or hammered flat. If that hood has a compound curve or a dome near the cut, getting the edge folded back against itself to that 120 degrees without really distorting the compound curve is going to be rough. You may have to cut the inside flange into short sections to even get it to bend, then once flattened, you have to deal with the multiple cuts on the underside fold.

Once it is folded back and flattened, you may be able to bring it back to its original form with a proper curve on the hammer form, but you will be reforming two pieces of metal that originally would have had the same curve but now have opposing curves in them. You will have to completely reform the curved lip that is folded under, as well as recurve the original curve on the top of the fold.

The double thickness edge will have some reinforcing stability, but without additional reinforcing it can be whipped by the wind and vibration. You are also adding a fold that can hold water and will allow rust to form between the pinched, doubled metal lip.

 

You guys are the best. I hadn't even thought about the fact that the contour will be the opposite way once folded over.. That's smelling more and more like a hammer form to me. As for reinforcing, the existing hood framing is only inches away and I expect that to do the job for stability.

Here's the victim, with the smaller piece in place and the hood cut, but not bend yet...

View attachment 6036413

 

Oh, and why? You might say... The hood is going to open from the windshield end...... The smaller piece which is the first 6 inches of a donor hood will be fixed.

 

I did consider a separate piece and welding, but I'm just not confident enough in my welding and grinding skills that I won't come out with a warped POS.

 

You would be farther ahead to make a 1/2" - 3/4 "L" shaped lip, formed to meet the contours of the end of the hood and spot weld or tack weld it along that rear edge to give the edge some structure. The shape of the end of the hood is going to be very difficult to just bend a 1/2" wide 90 degree bend and leave that alone, but that would add enough reinforcing to solve the flapping in the breeze problem I believe you will have without the reinforcing. Even if that hood end is sitting on top of bracing, its going to vibrate when driven down the road. The squeak and rattle that unreinforced hood end is going to make will be very distracting when ever you drive it.

Been there, done that. Learn from my errors, or go ahead and make the same mistakes on your own.

 

Are you saying leave the 90 on the tacked on 1/2" wide piece? Maybe I don't understand, wouldn't you be looking at 2 raw edges on the leading edge of the hood?

 

So you're wanting to hem the edge?



You won't want to use a brake.

Think of it as a door skin. Tip it to start the flange, hammer/dolly/shrink the flange to a 90, and then hammer it over to form the hem.

 

If you are going to be using a tipping die, it won’t happen all in one pass. Good: you will have opportunity to correct any wiggle you induced. Bad: you will need probably four guys to help do the job. Two holding the back edge of the hood, one turning the wheel, and you guiding the business end and shouting directions.

If you want to do the full and flat hem you probably won’t need to do any shrink/stretch along the way. Do the last roll of the hem between two flats on your bead roller. You will need to hammer and dolly the curve back into the front edge of the hood. Shouldn’t be too bad if your helpers listened well as you were rolling.

 

I truly appreciate all the helpful ideas, guys. I think I'll come up with a fence/guide for my bead roller first. Even with that I suspect keeping the hood traveling straight could be a challenge, but I think I'll at least have a chance. Without something like has been suggested, I don't think I stand a snowball's chance in Hell. Hmmm... maybe I'll cut up an old XJ hood I have laying around to try it out before the real one...

I also think making a hammer form beforehand might be prudent even if I don't end up needing it.

So, I'll tip it, hammer it over then run it thru the roller flat (thanks alchemy) then decide if I use the hammer form or if, by chance, just a little "convincing" is all that's needed.

 

I’ve only got experience with a rubber covered tipping set. Not sure if an all steel wheel would work differently.

 

Built a fence for the bead roller. Step 1, check...

 

If using a fence your cut needs to be exact. If tipping by following a line drawn on the part you have opportunity to adjust a little as you go. Slow and steady wins the race.

 

I plan to cut and grind smooth. I just can't picture 4 or 6 hands moving the hood and staying on a line without a guide like a fence... Got any suggestions?

 

Not really sure what your after but this panel was joined in the center of the bead.
The arc was made by patiently bending with a vice grip.

I haven’t bought a tipping die for my roller. I use pliers to bend flanges. Even hem joints.
Not the fastest but works
I have a pair of these that can fold further than regular vice grips

I’d like to try these