Tapping machine tap usually points single or group. Small and medium size through hole thread available single tap once tapping. When processing blind hole or large size screw hole often uses group tap, that is to say use more than two branches taps successively finish a screw hole processing.
Thread is the most common ways of mechanical part connection, tap is also the most commonly used tools of machining internal thread. So correctly choose tap machining internal thread, can guarantee the quality of threaded connection, improve the work efficiency.
Choose tap tolerance zone
China machine tap all logo intermediate diameter tolerance zone code: H1, H2, H3 respectively show tolerance zone same position, but the tolerance value is different. Hand tap tolerance zone code is H4, tolerance value, screw pitch and Angle error are larger than machine tap, material, heat treatment and production technology are not as good as machine tap.
Choose the thread system
At present common normal thread have three systems: metric system, inch system, unify system (also called American system). Metric system is based on mm units, thread tooth profile angle 60 degrees. Inch system is based on inch units, thread tooth profile angle 55 degrees. Unify system is based on inch units, thread tooth profile angle 60 degrees.
Choose tap type
Common tap types include: straight fluted tap, spiral fluted tap, screw tip tap, extrusion tap. Different kinds of taps, performance is also different, each one has his good points.
Straight fluted tap commonality is strongest, the price is the cheapest. Spiral fluted tap is suitable for processing blind hole thread, in processing chip out back. Screw tip tap processing thread chip out forward, has good strength and can withstand a larger cutting force. Extrusion tap is more suitable for processing non-ferrous metal, extrusion forming internal thread of metal fibre is continuous, tensile, shear strength is higher, the processing surface roughness is also better.