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The basic knowledge of fasteners (specification Part) describes the parameters of fasteners that need to be marked: product name (standard), specification, material, strength grade and surface treatment. Such as DIN912, m4-0.7x8, SCM435, grade 12.9, blackening.
1. Product name (standard): Note: for screws without standard, which are non-standard parts, drawings need to be provided.
For example, DIN912, the Chinese name is: Hexagon socket head cap screw, which is the product name.
However, the most accurate way is still to call the standard, because gb70 is also such a product name; However, the two standards are inconsistent in many aspects. The most influential standards in the world are German standards (DIN), international standards (ISO), Chinese national standards (GB), American standards (ANSI) and Japanese standards (JIS).
2. Specification. Generally, the designation of screw is tooth pattern diameter * screw length.
The commonly used metric system for tooth pattern diameter is m2, m3, M4, M5, M6, M8, M10, M12, etc;
The commonly used American systems 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, countersunk head screws are loaded with the total length, half countersunk head screws need to add the length of half head, while the length of cylindrical head screws does not include the head size. For example, for the specification, the full name is better to add the pitch. For example, m4-0.7x8, 4 refers to the tooth outer diameter of 4mm, 0.7 refers to the distance between two tooth peaks of 0.7mm, and 8 refers to the effective length of the embedded object of 8mm.
In order to simplify and not write the tooth pitch, we default the coarse teeth to the standard teeth, because it is the most common; So you don't have to mark it. This is the metric system. American products still need standard pitch.
Here we will focus on the specification of American screw. For example, 6 × 32 * 3/8 is the tooth outer diameter, which is close to 3.5mm; 32 is 32 threads per inch of thread length (equivalent to the pitch of metric screws); 3/8 is the length of the screw (specifically the same as metric screw).
There are two formulas to remember here: tooth outer diameter a \0=(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 data to be memorized. The number of teeth corresponding to each specification 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.
3. Material: the most common materials are carbon steel, stainless steel, stainless iron, copper, aluminum, etc.
Carbon steel is also divided into low carbon steel (such as c1008/c1010/c1015/c1018/c1022), medium carbon steel (such as c1035), high carbon steel (c1045/c1050) and alloy steel (scm435/10b21/40cr). Generally, c1008 is made of ordinary grade products, such as grade 4.8 screws and ordinary grade nuts; C1015 generally install eyebolt; C1018 is generally used to make machine screws. Of course, some are also used to make self tapping screws; C1022 is generally used to make self tapping screws; C1035 make grade 8.8 screws; C1045/10b21/40cr with grade 10.9 screws; 40cr/scm435 with grade 12.9 screws.
Stainless steel has 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 are called non authentic stainless steel products; The appearance looks similar to that of 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: grade 4.8, grade 5.8, grade 6.8, grade 8.8, grade 10.9, and grade 12.9. The nuts are grade 4, grade 6, Grade 8, grade 10 and grade 12.
Generally, screws below grade 8.8 are called ordinary screws, while screws above grade 8.8 (including grade 8.8) are high-strength screws. The difference is that high-strength screws need to undergo quenching and tempering heat treatment.
5. Surface treatment: the main purpose of surface treatment is to increase the anti-corrosion performance, and some also take into account the color, so it is mainly for carbon steel products, which generally need surface treatment.
Common surface treatments include blackening, galvanizing, copper plating, nickel plating, chromium plating, silver plating, gold plating, Dacromet, hot dip galvanizing, etc;
There are many kinds of zinc plating, including blue white zinc, blue zinc, white zinc, yellow zinc, black zinc, green zinc, etc. at the same time, they are also divided into environmental protection and non environmental protection. Each kind of plating has a variety of coating thickness to meet different salt spray test results.
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