Automotive or Aircraft punch/flare
 

Just wondering what you guys prefer?

I have used the automotive flares and I know it rounds the hole and has a 1/4" deep flare, where the aircraft puts a 35* bend with 1/8" flare.

anyone able to comment on which you prefer/why?

I prefer the automotive style, mostly based on aesthetics.

The deeper flare makes a slightly stiffer finished part.

Are you referring to Dimple Die sets? From what I can tell it is less about aircraft vs automotive than it is about the manufacturer of the die set. From what I have seen different manufacturers have slightly different designs. Rivet counter sinks are a little bit different story.

I think he is looking specifically at the Mittler Bros punch/die sets......I think.

Mitler bros as well as others have the two designs. I have used and actually have a couple of the automotive style punches/flares.

Was wondering if anyone used aircraft style and why they liked it. I can see pros/cons to both styles.

Just hazarding a guess here..... Aircraft are mostly Aluminum... and the curve and depth might be to reduce cracking.

I have the Mittler tools and have not seen cracking with 6061 T6. There are harder alloys like 2024 which might crack, but 2024 is for wing surfaces not bulkheads or interior panels. Aluminum will surely crack before Steel, & you do need to make sure your Belling Dies will work on aluminum.

Die by degrees
 

So no hatin' here, the aircraft flare/dimples were established waaaaay back as MS (Military Specifications) once the CAA (now known as the FAA) came into being the angles, fasteners, alloys ect were pretty much set. SAE developed the new angles in an attemped to prevent cross pollenization as they say.

As explained to me by a Airframe and Powerplant instructor. Might not make much of a difference to a car guy till they look out over a wing at 30,000 ft.

I have some rolled flares and angle flares both are from my aviation stuff. for car stuff its more about the aesthetics to me, for airplane stuff, its was about duplicating a part that needed replaced. Both will add strength but I doubt thats why your asking.