I was removing the exhaust manifold on my 1986 Turbo Diesel when it happened. My studs were doused with penetrant, and I was heating the nuts with a fine tipped oxygen-acetylene torch to a nice cherry color, and I still managed to break two studs.
I had a set of Milwaukee metal drill bits right handed, and set of Century Bits that cost $50 from Ace True Value that had never been used. I ordered these per recommendation of my auto mechanic mentor. The difference between the quality of the Milwaukee bits up to the Century Bits was about the same between the Century Bits up to the Irwin bits. On top of that the Irwin bits are half the price! These Irwin bits are SHARP, and HARD. I'm not saying these are the best bits on planet earth. But they cut better than a set of $50 left-handed bits, by a factor of 2.
I always use a mixture of F-type ATF and Acetone as a lubricant for my drill bit, and a penetrant on nuts and bolts. I dip the bit in synthetic (red) greese to collect any metal shavings that collect, and wipe it clean frequently.
The biggest reward was having the drill bit grab a hold of what was left of the stud and back it the rest of the way out. The beauty of left-handed bits!
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