Thread: Where to buy an 8-40 forming tap (or set)

It's not an oddball thread, its a standard imperial size. It's just not common in NZ any more. An 8-40 cut thread is fine in this size, but be aware that you will be removing the anodizing "hard layer" which won't make the thread last as a factory one would. If the ridge from forming is an issue, hand countersink it with a drill bit to remove the ridge, easy as. To be fair, you are removing the anodizing when you damage the threads anyway so if you want to recover the rings you don't have a choice.