Yes, it is stainless steel + bronze and it is indeed rather hard and tough. I use hard metal drill bits whenever possible. Even the HSS ones specially made for "normal" stainless wear much too fast. You are also right that it is very easy to break the smaller taps, because the torque needed is so large. Nevertheless, the smallest done so far was M1 for the screws holding the lid on the circle valve. The secret is to drill larger holes than the standard says, using high performance tapping grease and to make sure you tap straight. By the way, the tap you see in the last picture is an M3 thread former. I´m getting more and more fond of using formers since the day I managed to make 64 M1.6 threads in AISI 304 (1.4301 X5CrNi18-10) without breaking the tap (I did brake one or two drill bits, though). As you know, 304 is good for welding but hard to cut, since it cold hardens. In my experience, the stainless steel + bronze from Shapeways is even tougher than the 304.
