First, the parameters that describe fasteners need to be marked are: product name (standard), specifications, materials, strength levels, surface treatment. Such as: DIN912, M4-0.7x8, SCM435, 12.9, black.
1. Product name (standard): Note: For screws without standard, which are non-standard, drawings are required.
For example, DIN912, the Chinese name is: Hex Socket Head Cap Screw. This is the product name.
However, the most accurate method still needs to call the standard, because GB70 is also the same product name; but there are many places where the two standards are not the same size.
The most influential standards in the world are: German Standard (DIN), International Standard (ISO), Chinese National Standard (GB), American Standard (ANSI), Japanese Standard (JIS).
2, specifications, the general name of the screws are toothing name diameter * screw length.
Tooth pattern diameter, commonly used in metric system: M2, M3, M4, M5, M6, M8, M10, M12, etc .;
Commonly used in the US are: 4 # -40, 6 # -32, 8 # -32, 10 # -24, 1 / 4-20, 5 / 16-18, 3 / 8-16, 1 / 2-13, etc.
The screw length refers to the effective length of the embedded object. For example: the countersunk head screw is loaded with the total length, the half countersunk head screw is added to the length of the half head, and the length of the cylinder head screw does not include the head size. Such as:
For specifications, the full name is best to add tooth pitch. For example, M4-0.7x8, the outside diameter of the 4-finger teeth is 4mm, 0.7 means the distance between the two tooth peaks is 0.7mm, and 8 means the effective length of the embedded object is 8mm.
For the sake of simplicity, we do not write the pitch, we default the coarse tooth to the standard tooth, because it is the most common; so it will not be marked. This is only available in the metric system, and American products still need to be marked.
Here focus on the specifications of American screws, such as 6 # -32 * 3/8, 6 # is the outer diameter of the teeth, close to 3.5mm; 32 is 32 teeth per inch of thread length (equivalent to the teeth of metric screws Distance); 3/8 is the length of the screw (specifically the same as the metric screw).
There are 2 formulas to keep in mind here: tooth outside diameter A # = (Ax0.013 + 0.06) x25.4 (mm), 1 inch = 25.4mm.
Among them 2 # = 2.2mm, 4 # = 2.9mm, 6 # = 3.5mm, 8 # 4.2mm, 10 # = 4.8mm are the data to be memorized. The number of teeth corresponding to each type of screw must also be memorized: 2 # -56, 4 # -40, 6 # -32, 8 # -32, 10 # -24, 1 / 4-20, 5 / 16-18 , 3 / 8-16, 1 / 2-13 (American standard teeth).
Note: American UNC teeth are standard teeth and UNF are fine teeth. We default coarse teeth to standard teeth.