Through the investigation, we learned that many people do not have a clear description of fasteners. For example, some people want to purchase some fasteners, but when they talk about the details and what to buy, they always don’t know how to describe the fasteners they want to buy. As a veteran of fasteners, Xiaorui naturally understands it, and quietly tells everyone that when we describe fasteners, we can say from the marked parameters, which is clear and simple.
The parameters that need to be marked to describe the fasteners are: product name (standard), specification, material, strength grade, and surface treatment. Such as: DIN912, M4-0.7x8, SCM435, 12.9 grade, blackened.
1. Product name (standard): Note: For screws without standards, which are non-standard parts, drawings must be provided.
For example, DIN912, the Chinese name is: hexagon socket head screw, this is the product name.
However, the most accurate way is to call the standard, because GB70 also has such a product name; but the two standards have different dimensions in many places.
The most influential standards in the world are: German Standard (DIN), International Standard (ISO), Chinese National Standard (GB), American Standard (ANSI), and Japanese Standard (JIS).
2. Specifications: General screws are called the nominal diameter of the thread and the length of the screw.
Nominal thread diameter, metric commonly used are: M2, M3, M4, M5, M6, M8, M10, M12, etc.;
The commonly used American ones 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 embedded in the loaded object. For example: countersunk head screws are loaded with the total length, half countersunk head screws need to add half the length of the head, and the length of cylindrical head screws does not include the head size. like:
For specifications, the full name is preferably plus the pitch. For example, M4-0.7x8, the outer diameter of 4 fingers is 4mm, 0.7 means the distance between two tooth peaks is 0.7mm, and the effective length of 8 fingers embedded in the loaded object is 8mm.
For the sake of simplicity, without writing the tooth distance, we default the coarse tooth as the standard tooth, because it is the most common; so there is no need to mark it. This is only available in the metric system, and American products still need to mark the pitch.
Here we will focus on the specifications of American screws, such as 6#-32*3/8, 6# is the outer diameter of the teeth, which is close to 3.5mm; 32 is 32 teeth in the thread length per inch (equivalent to the teeth of metric screws distance); 3/8 is the length of the screw (specifically the same as the metric screw).
Here are 2 formulas to remember: Tooth outer 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 that must be memorized. The number of teeth corresponding to the screws of each specification 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: The US-made UNC tooth is a standard tooth, and UNF is a fine tooth. We default coarse teeth as standard teeth.
3. Material: The most common materials are: carbon steel, stainless steel, stainless iron, copper, aluminum, etc.
Carbon steel is divided into low carbon steel (such as C1008/C1010/C1015/C1018/C1022), medium carbon steel (such as C1035), high carbon steel (C1045/C1050), alloy steel (SCM435/10B21/40Cr).
Generally, C1008 is made of ordinary grade products, such as 4.8 grade screws and ordinary grade nuts; C1015 is generally used for ring screws; C1018 is generally used for machine screws, of course, it is also used for self-tapping screws; C1022 is generally used for self-tapping screws ; C1035 to play 8.8 grade screws; C1045/10B21/40Cr to play 10.9 grade screws; 40Cr/SCM435 to play 12.9 grade screws.
Stainless steel is SS302/SS304/SS316 as the most common. Of course, a large number of SS201 products are also popular now, and even products with lower nickel content, we call non-authentic stainless steel products; the appearance looks similar to stainless steel, but the anti-corrosion performance is quite different.
4. Strength grade: Strength grade mainly refers to carbon steel fasteners.
The common strength grades of carbon steel screws are: 4.8, 5.8, 6.8, 8.8, 10.9, 12.9. Nuts are correspondingly: 4th grade, 6th grade, 8th grade, 10th grade, 12th grade.
Generally, screws below grade 8.8 are called ordinary screws, and screws above grade 8.8 (including grade 8.8) are high-strength screws. The difference is that high-strength screws need to be tempered and heat-treated.
5. Surface treatment: Surface treatment is mainly to increase anti-corrosion performance, and some also take into account the color, so it is mainly for carbon steel products, which generally require surface treatment.
Common surface treatments include: blackening, galvanizing, copper plating, nickel plating, chrome plating, silver plating, gold plating, Dacromet, hot-dip galvanizing, etc.;
There are many types of galvanizing, including blue and white zinc, blue zinc, white zinc, yellow zinc, black zinc, green zinc, etc., and they are also divided into environmental protection and non-environmental protection. Each type of galvanizing has a variety of coating thicknesses to meet different needs Salt spray test effect.
Reminder: This is generally the marked parameter of the fastener, but if you want to elaborate, there are still many, for example, the nominal diameter of the thread in the fastener specification is divided into many, for example, there is a common thread (M) , pipe thread (C, Rc, Rp, R), trapezoidal thread (Tr) and zigzag thread (B), etc.
