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Screw accuracy grade
The grade of the thread is generally determined by drawings at the time of design of the threaded product.
To meet the thread accuracy of the drawing instructions, it must pass the inspection on the thread gauge.
The approximate application is as shown in the table, but please check the drawing instructions for selecting a gauge during thread processing.
Thread accuracy is expressed in the following grades:
Accuracy of various screws (grade)
| name | Screw Grade | ||||||
| Types of screws | division | Harsh ←←←←←← →→→→→→ Loose | |||||
| Metric Thread (M) | Conventional JIS | 1st grade | Level 2 | Level 3 | remarks | ||
| Current JIS | external thread | ４ｈ |
6h (M1.4 or less) 6g (M1.6 and above) |
８ｇ |
alphabet lowercase |
||
| internal thread |
4H (M1.4 or less) 5H (M1.6 and above) |
5H (M1.4 or less) 6H (M1.6 and above) |
７Ｈ |
alphabet capital letter |
|||
| Unified Screw (U) |
JIS ANSI |
external thread | ３Ａ | ２Ａ | １Ａ |
The unify screw is If you get 3, it will be a strict grade. |
|
|
JIS ANSI |
internal thread | ３Ｂ | ２Ｂ | １Ｂ | |||
| whitworth screw （Ｗ） | Level 2 | Level 3 | Level 4 | ||||
| Usage | Screws that require a snug fit | for general machine tightening | General Machine Utility Screws | Black Leather Bolt |
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*About the existing JIS and current JIS: The JIS standard for metric screws was revised in 1973.
See below for details. What is the revision of the JIS standard for metric screws?
The permissible limit dimensions for each grade (tolerance range class) in the typical size of metric screws are as follows.
