Why You Need Cobalt Drill Bits for Cast Iron
If you've ever tried boring through an old engine block or a vintage skillet, you already know that using cobalt drill bits for cast iron is pretty much the only way to keep your sanity. Cast iron is a weirdly deceptive material. On one hand, it's brittle enough to snap if you hit it with a sledgehammer, but on the other, it's abrasive and tough enough to turn a standard high-speed steel (HSS) bit into a glowing, useless nub in about ten seconds. ...