As we know, old zinc prewar flanges are brittle and tend toward breakage. After a traumatic experience with UPS, I found myself with a broken flange to my 1930 Florentine. Since the value of this rare instrument is very much bound up in this particular part, I set about to repair it, come hell or high water. I'll tell you this takes patience, as I broke more of the flange at first as I tried to fix it. It seemed hopeless at one point, but the key was getting used to working with SteelStik epoxy putty made by JB Weld. This is amazing stuff that gives you about 5 minutes of work time and then hardens all at once. Bottom line: You can be your own clamp. I reinforced the breaks with customized washers and aluminum strips underneath. On the front side I filled in the cracks (where needed) with drywall mud and then finished the areas with 24kt gold leaf. Granted, there is a lot going on with the engraving on this flange that makes the repairs less noticeable. I'm thinking you could still use the same repair technique on a nickel flange and finish it with silver leaf. Or if you can join the cracks cleanly enough, you probably don't need any cover. BE AWARE, the repaired section will never be as stable as the original zinc (weak as it is), so you need to go easy and not push, pull or park your car on it. Be especially careful not to push down on the flange when you reseat the banjo on the resonator (like I did...). I hope this furthers The Knowledge about how to fix these wonderful old instruments.
I believe you can repair a pot metal flange, but it will eventually fail in another place. It might be more practical to invest in a new flange for playing, but keep the old flange tucked away for posterity.
In my other life I restore old violins. Some are 200+ years old. You repair their injuries, bring them back to life and they sing. Some repairs will last 100 years. Others won't and a future luthier will step in and continue the tradition -- and probably with new techniques and materials. Old Gibson banjos are no different.
Be especially careful not to push down on the flange when you reseat the banjo on the resonator (like I did...).
I really appreciate that last piece of advice about not pushing on the flange! I have been pushing on the flange of my early SSS TB-11 to seat the banjo securely in the resonator (carryover habit from newer banjo), and never thought much about it, until now. Thanks! Also, your repair looks great!
Yes, a high bridge was looking pretty good when UPS did its number. The pot was on the way to having the new neck fitted by Renee Karnes in California. I had the banjo heavily insured and I did receive a reasonable settlement for the damage. But a one-piece Florentine flange is as rare as hens teeth. Engraving and replating another prewar nickel flange was an option as a replacement, but it dramatically reduces the value of the instrument. Necessity is a mother...