Screw thread insert (STI) taps create an oversized thread inside a hole so that a helical-coil screw thread insert can be installed in the hole. The insert distributes the load across the length of the threads and improves the threads' strength when a fastener with a standard screw thread size is screwed into the hole. Straight-flute STI taps move chips into the taps' flutes but do not evacuate the chips during threading. Spiral-flute STI taps pull chips out and away from a hole during threading, which helps prevent chips from packing in the hole. Spiral-point STI taps push chips in front of the tap during threading and eventually force the chips out of the hole, which prevents chips from clogging in the taps' flutes. Thread-forming taps produce cleaner, stronger, and more accurate threads than STI taps that cut threads, and they don't create chips. Pipe STI taps create internal threads in thread standards and sizes that are used on pipe and pipe fittings.