What is the screw model and size specification table?

1, screw size code is m, h and g, in which internal threads are marked with capital letters and numbers, including 7H and H7.

2. External threads are marked with lowercase letters, such as 6g and g6, where 6g represents the tolerance of threads, g6 represents the tolerance of cylinders, code 7h represents the tolerance of threads, and h7 represents the tolerance code of cylindrical threads.

3. In addition, screws are divided into left-handed threads and right-handed threads. The lengths of left-handed threads are marked with L and H, and the rest are right-handed threads.

4. Usually, the length of the screw is expressed by sml. Generally, the length of the screw is not marked, and only these letters are used, such as m20, 5g and 6g.

Extended data:

Applied common sense

1. First, remove the silt on the surface of the broken wire, countersink the center of the section with a center chisel, and then use an electric drill to mount a bit with a diameter of 6-8 mm to countersink the hole in the center of the section, paying attention to the hole must be drilled through. After the hole is drilled through, remove the small drill bit and replace it with a drill bit with a diameter of 16 mm, and continue to expand and drill through the hole of the broken bolt.

2. Take covered electrode whose diameter is less than 3.2mm, and carry out surfacing welding in the hole of the broken bolt from inside to outside with medium and small current. At the beginning of surfacing, take half of the total length of the broken bolt. When surfacing welding is started, the arc should not be too long to avoid burning through the outer wall of the broken bolt. After surfacing to the upper end face of the broken bolt, continue surfacing to 14- 16 mm in diameter and 8- 10 mm in height.

3. After surfacing, knock the end face with a hammer to make the broken bolt vibrate along its axial direction. Due to the heat generated by the previous arc and the subsequent cooling and vibration at this time, the thread between the broken bolt and the machine body will become loose.

4. Observe carefully. When there are traces of rust leaking from the fracture after knocking, the nut of M 18 can be sleeved on the surfacing column head and welded together.

5. When welding is hot or cold, put a ring wrench on the nut and twist it back and forth. You can also twist back and forth while tapping the nut end face with a small hammer to take out the broken bolt.

6. After taking out the broken bolt, process the thread on the frame with a suitable tap to remove the rust and other sundries in the hole.

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