To sharpen carbide bits, look for a sharpener that comes with diamond wheels ... won’t have the hard coating that makes them so useful. Q. How often should you sharpen drill bits?

The DC180 Supreme drill comes in two grades: The WJ30EZ grade has a K30F fine-grained carbide substrate with a multi-layer aluminum titanium nitride (AlTiN) coating; and the WJ30EY ... consists of ...