I little tip I picked up years ago was to save the filings, and bits of metal kicked out when filing or drilling any type of metal. You can also cut up some steel wool with scissors into little small bits. When I mix up my JB Weld, I add some of this mix into it to strengthen the mix. About one third to one half of the total volume. It makes for a very solid repair, that can still be smoothed, drilled, or even drill and tap it. I've only ever used it with JB, but I imagine that it'll probably work with any epoxy compound.