ARTU 1505 5-Pc. Multi-Purpose Drill Bit Set

I discovered these a couple years ago while looking for a way to drill out some tempered Knife blade tangs. in my drill press on max rpm you just press firmly and watch the thing plough right through. the part you are drilling will throw cherry red shavings and while typically that's a bad sign with traditional bits, these seem to work best under those conditions. the bits don't seem to get damaged, even after several holes. most recently I used the 3/8 bit to convert some 10 round sig mags to the standard 15 round. I accidentally bought the California legal mags and couldn't return them. sig mags are made of fairly hard tempered steel and this bit converted them in a few minutes with nice fairly clean holes. you still have to chamfer the edges a little to remove the sharp edge but the bit went through like butter. I haven't tried these on more exotic hardened tool steels like S7 or 10v, and I have a feeling those kinds of steels will probably destroy the bit because they are sometimes difficult to even professionally mill and very hard on tooling. but regular general purpose stuff like 1095 or 01 haven't been an issue.