I ran across these sheet metal dimple dies watching Hoonigan the other day. I think the concept is good that it cuts the hole and dimples at the same time.
https://www.eastwood.com/eastwood-punch-and-flaring-dies.html
Regular dimple dies are cool too & I think it would complement our shop.
Dimples add a fair amount of rigidity to a panel while lightening it at the same time. Great for pass-through holes for wiring or lines. If running these through sheet metal holes suggest something like these
This type is great for tight curves. Search term: “Grommet Edging”
Note: joint properly should be at top of hole so if for any reason it opens up wire won’t rub against metal. Yeah it’s a nit, but details count.
Punch for prepping chasis for tube based project.
Is your framee less than 16 ga??
Chassis vary in the metal and ga.
I remember seeing a variety of Greenlee punches sized for tube sockets in the various electronic mags.
You grew up near where the Apollo Command Modules were built. What direction is up on a spacecraft. Or do they make seamless grommets for that?
On the launch vehicles parts I’ve worked on (mainly Saturn second stage, some ISS), up was opposite the launch force, at least that was how the drawings would have indicated by placement. But then again, they only had survive a few minutes. Vibration dampening was a major consideration - don’t recall any large holes where something passed through that wasn’t clipped or restrained so it could vibrate. Insulating blankets (thermal and sonic) had woven stainless steel cloth panels - about 200 threads per inch, in them to allow the heated air caused by sonic vibration to escape so they wouldn’t explode. Rocket motors cause intense vibration.
On orbiting or zero G vehicles, I’d bet they used sized one piece grommets plus restraints. Expense wasn’t an issue, so they could have them made - and special designs that were light weight. Space craft are in a league of their own with redundant systems, special materials, etc.
Amazing timing this came up. There was a guy going through the tour last Thursday very specifically asking if we had dimple dies. Another member continued discussing various items on the subject but we indicated we don’t currently have them. Maybe it’s a sign we should. 
My bad, thinking of different kind of chassis.
I didn’t see a lot dimpling on commercial aerospace sheet metal since you had to prep the underlying sheet to accommodate the displaced metal. Usually there were countersinks so flush-head fasteners (almost also rivets) could be used.
If a dimple was used, the underlying material usually had something similar to a countersink put in, don’t ever recall seeing a dimple into a dimple, not sure how well the upset would work since it would be wider in diameter than dimple at the exit and would cut into the upset as it was trying to form downward and would probably want to push to manufactured head out so it wouldn’t seat properly.
Hole prep and fastener attachments were unbelievably spec’d out.
If you dimple the top sheet (for flush riveting) you can dimple the bottom sheet too if it is thin enough. Otherwise you countersink.
If you get dimple dies then you need a squeezer or c-frame to use them. They’re also expensive and will break if abused.
Did we ever wind up getting the dies and press for these?
Unfortunately we haven’t.