There was recently a thread with instructions on how to make taps "the old fashioned way". In the past I've tried to grind homemade taps in the same manner as commercial ones and had no success at all. I needed a M6x0.35 tap, so decided to give it a try. Cut the appropriate sized thread on a piece of O1, heated the tip to red and quenched it. Then I ground four 30 degree flats, a bit hollow from the wheel actually. I was skeptical, but by gosh, the thing cuts like a dream. Can't remember the thread, but my thanks to whomever suggested this.