How to distinguish between good and bad batches?

Bits made of good materials do not require surface decoration. The surface of a good bit is the color of the steel itself, which is exactly the same from the inside to the outside. The quality of the bit depends on the inner material and whether its hardness can reach the standard of use. It cannot be too high or too low. Too high hardness can easily cause brittle fracture, and too low hardness can easily cause slippery teeth. In addition to hardness, it also depends on the torque of the bit. Before the batches leave the factory, the torque test is done to increase the torque limit as much as possible. The precision of the batch head should meet the needs of precision assembly production, and the precision of the batch head should be good.