cobalt drill bits are the only answer. These powerful drill bits for cast iron, aluminum, and even stainless steel are made ...

It turns out that a hot solution of alum (ammonium aluminum sulfate), which is available in the spice rack of your local supermarket, will dissolve the steel ... for larger drill bits, but the ...

We learned a lot by sharpening 100 dull drill bits, including carbon steel, high-speed steel, titanium-coated, and cobalt options. Some of the sharpeners were less expensive and others were easier ...