I need to drill and ream a 4 mm dia 55 mm deep hole in Inconel X-750, which is hard as something-or-other, a lot harder than even masonry nails though, or perhaps just plain tougher as well, though it can just about be machined with newly sharpened HSS tools. Mind, I lose about 1/10th of an inch of parting-off blade every time I part off a 12 mm rod of the stuff, it needs sharpening twice, and facing one end of a 12 mm rod blunts a tool. But it's doable.
This darn hole doesn't seem to be doable. I have tried HSS, cobalt HSS drills (which it doesn't even deign to sneer at), Wickes carbide tipped "universal" drills (about 3 mm deep, after sharpening - the original drill didn't cut at all - then the tip fell off), TiN (which got me about 5 mm deep before the coating went) and have broken two cheap solid carbide drills (and two brand new centre drills).
Help! Any suggestions? Drilling in the lathe, coolant, anything else?
A good tough solid carbide drill is about the only thing I can think of that might have a chance - somewhere around 1/8" - 3.5 mm dia, and longish, though at a pinch a jobbers drill would do - anyone know of a supplier?
Any other tips for working with metals from hell?