About the screw 'standard'
- JIS standard of screw
- "JIS standard" and "ISO standard" of screw
- About special screw
- Contents of screw standard
Even if you say "screws" at one bite, you can see that there are many screws in the world, as many screws are sold at home centers. The "standard" is used as an index to identify such screws. So, I will explain the standard of the screw.
JIS standard of screw
Screws are classified into the following standards in JIS (Japanese Industrial Standards).
- 〇Metric screw (coarse thread)
- 〇Fine screw (decommissioned in 1998, integrated into coarse screw)
- 〇Metric trapezoidal screw (metric taper screw)
- 〇Unified coarse screw
- 〇Unified fine thread screw
- 〇Parallel thread for pipe
- 〇Pipe taper screw
- 〇Wit screw (discontinued)
"JIS standard" and "ISO standard" of screw
The screw standard is an essential standard to identify the required screw type in consideration of performance and safety. In addition to the above-mentioned "JIS standard", the standard of such a screw has the "ISO standard" which is an international standard.
The JIS standard follows the ISO standard, which is an international standard. Therefore, the difference between the two is decreasing, but the JIS standard remains because, in practice, the size of the screw does not exist in the ISO standard. If you are looking for screws in Japan, basically there is no problem if you refer to the JIS standard.
About special screw
As long as the standards are the same, a screw made by any manufacturer will basically be a screw with exactly the same size and angle of thread. So, if you know the required screw standards, you can basically use any screw made by any manufacturer.
However, there are cases where standard screws can not achieve the purpose of using screws. When used for complex shapes and special applications, existing standard screws may not be able to cope. In that case, it is necessary to have the manufacturer make a "special screw".
Special screws may be manufactured from one point by some manufacturers, or may be mass-produced if necessary.
Contents of screw standard
The threading standard uses the following designations and dimension ranges.
- ■Outer diameter:Designated by M で screw, etc., M means "meter", and the number means "outer diameter (diameter of threaded shaft)"
- ■Valley diameter:Diameter based on thread groove
- ■Effective diameter:Theoretical diameter at which thread width and thread groove width are equal
- ■pitch:Distance between adjacent threads
- ■Thread angle:Angle of the screw thread (screw thread)