Bangle core: stainless steel
I have received quite a few emails after I posted the problem with the "broken bangle core", asking what gauge of stainless steel is recommended. I used 24 ga, which is pretty thin and it was already very DIFFICULT to make a wrapped loop with that -- so I don't recommend any thicker. The wire I used is the kind that is sold sometimes as "memory wire", and is easily found in jewelry supply stores.
The advantage of using the stainless steel core is that, because it's thinner, you can use nicer stones to make bangles (which normally come with very tiny holes), and it will hopefully not break unless you are really *ruthless* with the jewelry.
The disadvantages are that it's tricky to make a wrapped loop with such hard wire, and you have to wrap the core wire ENTIRELY, even the loops and shanks, or else the bangle looses some of the preciousness. (If you are going to take that long to make a piece of jewelry, it better look precious!).
Oh, another disadvantage is that the stainless steel is REALLY hard to cut. Don't you use your good cutters on it or you'll ruin them. Instead, get a pair of strong regular wire cutters from the hardware store.