[mentorDon]

The drill/tap combo (DRAP) is best used on a CNC machine. The amount of material thickness must be less than the drill length of your tap of course. No blind holes! And for your case, the inside diameter of the pipe must be larger than the combined length of the cutting portion of the drap. The machine is programmed at a surface speed for drilling depending upon material and diameter. A feedrate is calculated to match material and speed. At a programmed 'z' depth after material brake through, the spindle speed is reduced and a new feed rate to match the rpm and pitch of the thread. After reaching the lower 'z' setpoint, the spindle is reversed and the tapping portion is fed out using the previous feedrate. Once the tool is clear, spindle direction is reset to clockwise, rpm increased, and moved to the next location. There are special tapping heads with springs to allow for inaccuracies of rpm and feedrates.