Tap, it is a kind of machining internal thread cutting tool, along axial direction open groove, also called screw tap.

According to the shape of the tap, can be divided into straight fluted tap, spiral fluted tap and screw tip tap.

1, straight fluted tap, its commonality is strongest, through hole or blind hole, nonferrous metal or black metal processing, price is the cheapest. But pertinency is poorly, anything can be done, but are not doing the best. It is commonly used in ordinary lathe, drilling machine and tapping machine screw thread machining, cutting speed is slower.

2, spiral fluted tap, is suitable for processing unfair hole thread, processing chip out back. Because of the spiral Angle, tap actual cutting rake angle will be increasing with the increase of helical Angle. For example: when processing ferrous metal, choose the smaller spiral Angle, generally about 30 degrees, to ensure the strength of the helical gear. When processing non-ferrous metal, choose the larger spiral Angle, about 45 degrees, cutting sharp. Spiral fluted tap usually used in numerical control processing center drilling blind hole, processing speed is faster, precision is higher, chip removal is better.

3, screw tip tap, chips discharge forward when processing thread. Its core size design is bigger, strength is better, can bear bigger cutting force. Processing non-ferrous metal, stainless steel, black metal effect is very good. When processing through hole thread, should first uses the screw tip tap.

According to different processing method, can be divided into cutting tap and extruding tap.

Of extrusion tap is more suitable for processing non-ferrous metal, with the above cutting tap working principle is different, it is to squeeze the metal, make it plastic deformation, forming internal thread. Extrusion forming internal thread metal fibre is continuous, tensile, shear strength is higher, processing surface roughness is also better, but extrusion tap bottom hole requirement is higher. If the bottom hole is too large, base metal quantity is little, causing internal thread path is too big, strength is not enough. If the bottom hole is too small, closed extrusion metal has nowhere else to go, it is easy to cause broken tap.

Of course, according to the method of use, tap also has types of hand use or machine use. No matter hand use or machine use, are master tap what cutting common thread. However, habitual called machine tap of manufacturing higher precision high speed steel ground tap, called hand tap of carbon tool steel or alloy tool steel roll teeth(or ) incisor teeth tap. Visible, tap is essential tool of currently manufacturing operators processing thread.