The distance between two adjacent teeth on the middle diameter line corresponding to the two points in the axial direction is called the pitch. On the same spiral line, the distance between the adjacent two teeth on the middle diameter line corresponding to the two points is called the lead. The relationship between the number of lines n, the pitch P, and the lead S is: S=n·P
When viewed in the direction of the axis, the thread that rotates clockwise becomes a right-handed thread, and the thread that rotates counterclockwise is called a left-handed thread.
The thread shape, large diameter, pitch, number of lines and direction of rotation are called five elements of the thread. Only the inner and outer threads with the same five elements can be screwed together.
It is important for the screw itself and is also important for products that require screws. The screw itself refers to the quality of the screw. For products that use metal screws, this is related to the hardness of the screw, can not be used on the product, this screw can not be driven into the product or twist the nut. The screws we produce generally need to pass the stop gauge. The meaning is that the general rules must be passed, and the rules must be stopped.
Screw thread is super important for the quality of the screw. If the head is good, the screw thread can't pass the stop gauge and can't meet the customer's requirements. Then the screw can't be considered a good screw. Some customers have higher requirements for screw threads, and generally need to pass the stop gauge. But some customers don't need it. However, if you want to use the screws used in the nuts, you usually need to pass the stop gauge.