The most commonly used taps are extrusion taps, spiral groove taps, straight groove taps, tip taps, pipe taps, nut taps and hand taps, which have different uses and different performances.
Extrusion tap (NRT)
The difference between extrusion tap and cutting is that there is no cutting discharge during tapping, while the machined surface of internal thread is made by pressing and has a beautiful appearance Smooth.
The material iron wire is not cut continuously, the thread strength is increased by about 30%, and the accuracy is stable.
Due to the large core diameter of the extrusion tap, it has high endurance and torque strength, long service life of the tap and is not easy to break. Suitable for materials with high ductility.
Iron plate, copper plate, aluminum plate, stainless steel plate and pipe processing.
However, the requirements for the bottom hole of the extrusion tap are high: it is too large and the amount of base metal is small, resulting in too large internal thread diameter and insufficient strength.
If it is too small, the closed extruded metal has nowhere to go, causing the tap to break.
The calculation formula is: bottom hole diameter = nominal diameter of internal thread – 0.5 pitch.
Spiral groove tap (SFT)
The spiral groove tap has a good effect on tapping in the blind hole and cutting the continuously discharged steel material.
Because the right-hand spiral groove cutting of about 35 °can be discharged from the hole, the cutting speed can be 30% – 50% faster than the straight groove tap, and the high-speed tapping effect of the blind hole is good, because the cutting is smooth.
It has poor effect on materials such as cast iron cut into fine pieces.
Straight groove tap
Straight groove tap: it has the strongest versatility.
It can be processed through or through holes, nonferrous metals or ferrous metals, and the price is the cheapest.
Related reading: Ferrous vs Non-ferrous Metals
But the pertinence is also poor. We can do everything and do nothing best.
The cutting cone can have 2, 4 and 6 teeth.
The short cone is used for through hole and the long cone is used for through hole.
As long as the bottom hole is deep enough, the longer cutting cone should be selected as far as possible, so that there are more teeth sharing the cutting load and longer service life.
Tip tap (POT)
Because the front edge groove of the leading tap has a special design of the barrel edge groove, it is easy to arrange and cut, with small torque and stable precision, which improves the durability of the tap to a higher level;
When machining threads, the chips are discharged forward.
Its core size is designed to be large, with good strength, and can bear large cutting force.
The effect of processing non-ferrous metals, stainless steel and ferrous metals is very good.
The leading tap should be preferred for through-hole threads.
Pipe tap (SPT)
There are two kinds of pipe taps: PF (G) thread tap based on mechanical combination (JISB4445) and thread oblique tap based on tightness (JISB4446).
There are inclined thread taps PT (RC) and straight thread taps PS (RP) for pipes, as well as American thread taps NPT, NPS, NPTF, etc.
Nut tap (SNT)
Nut taps are specified in JIS, which are mainly used for tapping processing of nuts.
Considering the processing characteristics of nuts, the tooth and shank are relatively long (JJS4433).
JIS specifications include long shank taps and short shank taps, but the tooth length is the same.
Hand tap (HT)
The straight groove shape of hand twisted wire cone is generally widely used and is the most common.
JIS stipulates that there are food and pay lengths divided into 1# (9 mountains), 2# (5 mountains) and 3# (1.5 mountains).
Three branches are combined into a group, and the working energy rate can be increased.
Single tapping teeth can also be used.