One characteristic of the faucet is that the lead in the grooves is the number of teeth per slot, which is actually used to remove the material. The larger the number of teeth, the less of the cutting force required for each tooth, so the likely lifetime of contact will be longer. So, whenever possible, increase the chamfer length of the tap. The valve is designed to be applied through the hole, and the final thread form is not limited by the hole bottom, which usually USES a slot hole of 3.5 to 5 threads. Holes used for blind holes or holes usually require a bottom or semi-contact tap, with a shorter slot between 1.5 and 3 threads.
The two most common touch base contacts are type E and Form c, sometimes referred to as “full” bottom taps, in which the type E faucet has 1.5 to 2 threads. The C – shaped tap is sometimes referred to as a semi-contact tap, because the length of the slot is 2 to 3 threads. In most applications, c-type is the best, because the length of the chamfer has slightly increased, so the cutting force of each tooth is reduced. When a part is pulled out, a full thread is required at the bottom or near the hole. The bottom contacts usually have a spiral flute design to pull the chip out of the hole.
The faucets of type B groove are 3.5 to 5 threads, which are called plug or hole taps. The most common plug-type plug is the “spiral point” plug (also known as the “barrel of a gun”), and its cutting edge is easier to replace than the edge of the center line. This feature allows the faucet to continuously break the chip and spray it into the slot to prevent the chip packaging. This improves the efficiency of the faucet, but is usually only used when holes are made.