Common thread has coarse tooth and fine tooth cent, same nominal diameter can have a variety of pitch, among them the person with the largest pitch is called coarse tooth thread, the rest is fine tooth thread.
Along the axis direction, clockwise rotation of the thread becomes right-handed thread, counterclockwise rotation of the thread is called left-handed thread.
The tooth type, large diameter, pitch, line number and rotation direction of the thread are called the five elements of the thread, only the five elements of the same internal and external threads can be rotated together.
Coarse teeth: do not need to mark the pitch, such as M8, m12-6h, m16-7h, etc., mainly do connection thread use, and fine tooth thread than, because the pitch is large, the thread Angle is also large, poor self-locking, general and spring washer with the use: pitch is large, the tooth is deep, the strength of the body is also large.The advantage is easy to disassemble and assemble, with its complete set of standard parts, easy to exchange.
Fine thread: must indicate pitch to show difference from coarse thread, characteristics and coarse thread on the contrary, in order to supplement coarse thread can’t satisfy the special requirements and regulations, also have fine thread pitch series, mainly used in hydraulic system of metric pipe fittings, mechanical transmission parts, insufficient strength of thin-walled parts, being limited by the space of machine parts and self-locking to demand higher shaft etc.
Judge screw thread is coarse tooth or fine tooth, judge the use of screw thread roughly first, measure the length of n pitch with caliper of uncertain reoccupy, after dividing n computation, check screw thread table again can.
Characteristics of coarse and fine teeth（bolt）：
1, fine teeth spiral Angle is smaller, more conducive to self-locking thread, so fine teeth generally used in the need to prevent loose places.
2, fine tooth thread pitch is small, in the same thread length, more teeth, can play a role in reducing fluid leakage, so it is used in the need to seal the occasion.
3. Less teeth of the same length of coarse thread, larger section size of each tooth, better stress, more suitable for bearing larger pulling force and impact force.
4, fine tooth thread should also have the advantage of small pitch can play the role of fine tuning
Post time: Aug-05-2019