slotted and or drilled rotors

MISF (called that to protect him) drilled his street car rotors in about 1988. They cracked from the holes, rapidly. He drives all of his vehicles pretty hard. Told me that he felt no gain and I know that it took a long time to do. He hasn't done it since. I'm sure that he did everything wrong because that's how he usually does things, but it serves as a worst case example in my book.

69_340_GTS said

I work as an engineer in jet engine repair. A lot of times a small crack can be stopped by drilling a hole at its end. How does the "stress riser" crowd explain that?

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Presents a discontinuity to the crack. That means that it does stop the crack, but that doesn't mean that new cracks can't propagate from the hole. Many times in castings the crack is following a slight flaw or was started by a slight flaw. Those flaws are also stress risers or the crack would not have developed unless the part had too low of an SF.

This is all well documented stuff, find a Carroll Smith book ("Engineer to Win" being the best one) if you're not into dry engineering reading.