This is a ballpark figure to calculate thread depth. I had forgoten to mention, be sure to touch off your tool carefully and accuratly. A deep touchoff or starting point will potentially cut your pitch dia. too deep. I also neglected to say this calculation is for single depth. If your machine has 1 for .001 dials you have to double the sum of your equation. An evan simpler equation is .866 divided by # of threads Ex: 1/2-13= .866 / 13= .066 Dont forget the -.005
