Now tap brands on the market a lot, due to the use of different materials, with the specifications of the price a lot of difference, so that buyers like smoke and mirrors, I do not know what a good buy, Changzhou too good to teach you the following a few simple ways:
     When buying (because there is no testing equipment, except slotless taps) can simply detect (M6 for example):
     1: Look at the front end of the threaded tap Grinding (chamfered) is uniform, whether there are fast cutting blade slot mouth, good positively seven fonts, bad inverted seven words or U-shaped (will cause twice when exiting wire tapping cutting, easy to break and affect the accuracy of the thread);
     2: Detection heat treatment conditions: Tap into the air pull parabola (5 meters) level fall is broken, broken description brittleness;
     3: knock off the tap to see if it is plagioclase fracture, fracture in the molecular particles (microstructure 10.5 #) fine knot, indicating that the heat treatment and the material is good, flat or inclined too short, molecular particles (microstructure) the crude is not good.
     For good or bad depends on tap its original material, heat treatment, groove, precision, equipment, speed and processed material, hardness, and so the quality of the operating staff have a relationship! The selection of tap, tap on the original material, heat treatment, groove to pay special attention, for different machining holes, it is recommended to choose different types of taps!