I quickly calculate proper tap-drill diameters using this simple formula. Tap-drill diameter equals nominal diameter minus thread pitch. I quickly calculate proper tap-drill diameters using this ...

I just got a set of Dewalt Titanium drill bits with the hope of reaming out a couple of holes that were too small. One hole was .49" and needed to be .5", and the other was .36" and needed to be .375" ...

When I was drilling through a hardened steel I went to a specialty metals shop and they recommended cobalt bits. They were also much cheaper than lows but unfortunately have since gone out of business ...