When tapping thin sheet metal, is there a general rule of thumb regarding how many threads there should be? I get the impression that the thinner the sheet, the more threads per inch there should be so that there are enough threads in the thickness of the panel. In order to save some cash, I'm looking to use 1/16" stainless if possible. What size screw should I be looking at for this size metal? Or does it not really matter?
That would be tapping. Not taping. And yes, the more threads per inch yields more thread to hold on to. But why not reinforce it with another piece of SS bonding it with either JB Weld or some other thing.
I could never get it right, whether it was 'taping' or 'tapping'. Either way I fixed it. I'd rather avoid JB Welding another plate to add thickness. That complicates things and detracts from the clean look that I'm going for. If 1/16" is too thin to tap, I'll just use 1/8" aluminum. It's cheaper though I was hoping to use SS for it's durability.
I'm curious. Wouldn't the bonded piece be hidden behind the sheet? It wouldn't have to be a big piece, either. It could be a nut bonded to the back of the sheet.
I'm sorry, I should have been more clear. When I said that it would 'complicate things', I meant that it would be a pain in the ass as well as ruin the case's structural integrity. I plan on using square tubing so placing anything on the opposite side would be near impossible without hacking it up.
Hm... the only good method I had when doing this in the past was to JBWeld a normal nut to the backside of the sheet metal, and use a normal hole. You simply can't get reliable threads on metals that thin, or at least not for any screw size that's structurally useful. Not ideal, but short of riveting things into place (don't, unless you know you never want it apart again - drilling them out is always a pain), I think an epoxied on nut is probably going to be the only thing that works.
normally you would need 3 threads to make a good threaded hole. On most threaded holes in cases, the hole is pushed backwards, so that there is more room for threads, I'm not sure how that is accomplished though.
Generally, only a very small hole is drilled (say 1.5mm for an M4 hole), then a (for e.g. 4mm) punch is driven through the small hole. this enlarges the hole, while bending the edge back so it can be tapped.
capnPedro is right you can add more thickness using a punch(it shifts material back), but for 1/16th stainless you should be able to use a size up to Metric 5mm. I like metric because of the fine threadswhick give it stability in the hole.
