These seem to be very popular lately. You see the dimple holes for roll bar gussets, mounts, etc. I picked up a quality dimple die / punch die set from a downsizing shop. The question is: do these type of dimpled holes belong on traditional rods, old school race cars, gassers etc. I believe they date back to the early aircraft industry. Seems most of the old photos I've seen have lots of swiss cheesed sheet metal cut with regular hole saws.
They may be a little too "professional" for a traditional car or Gasser because a lot of work back in the day was crude by today's standards. Hole saws and holes cut by torches were pretty common back then. With that being said, I would still use a dimple die even if I was building a traditional car, Gasser, or whatever. To me, they make a better, cleaner hole and look a lot more professional. Then again, I'm am biased. I've been in the aviation field since 1981, and I expect things to look a certain way, even if it might offend the purists. I like the look of a dimpled-died hole versus a hole-sawed hole. Less prone to cracking, also.
You're probably right Shakey. "Back in the day" young guys didn't even have hole-saws, most guys drilled a bunch of 1/4" holes to make a 2" hole We are lucky to have all these great tools available. Next we'll be building hot rods on a 3-d printer.
http://www.jalopyjournal.com/forum/showthread.php?t=746432&highlight=belled+holes Bell mouthed holes use male and female dies. Conventional drilled holes from my understanding lightens and weakens the material, adding the bell ridge strengthens the material whilst retaining lightness.
Great thread on here a while ago about the very subject. It was started by, I believe, "Falcongeorge". Very informative.
Here, this will teach you to do it with out those expensive dimple dies. http://www.youtube.com/watch?v=ja6F2xchLzU
The Jalopy Journal
