Basic Knowledge Summary for Fastener
Description of fasteners needs to be marked with the following parameters: name (standard), specifications, material, strength grade, surface treatment. For example, DIN912, M4-0.7×8, SCM435, Grade 12.9, blackened.
1,Name (standard)
For example, DIN912, the Chinese name: hexagonal cheese head screws, is the product’s name.
But the most accurate practice, or the need to call the standard, because GB70 is also the same name; but the two measures have many places where the dimensions are not consistent.
The world’s more influential standards are German standards (DIN), international standards (ISO), Chinese national standards (GB), American standards (ANSI), Japanese standards (JIS).
2,Specifications of fastener
General screw designation is the diameter of the tooth pattern designation * screw length.
Tooth pattern called the diameter, the metric system commonly used: M2, M3, M4, M5, M6, M8, M10, M12, etc.
American system commonly used are: 4#-40, 6#-32, 8#-32, 10#-24, 1/4-20, 5/16-18, 3/8-16, 1/2-13, etc.
And the length of the screw is the adequate size buried into the object being loaded. So, for example,, countersunk head screws are loaded inas the total length, half countersunk head screws add half the head length, while the length of the cylindrical head screws does not include the head size, for example.
For specifications, the full name is preferable to add the tooth pitch. For example, M4-0.7×8, four refers to the outer diameter of the tooth is 4mm, 0.7 refers to the distance between the two crests of 0.7mm, 8 refers to the effective length of 8mm buried in the object being loaded.
To simplify, do not write the tooth distance; we default the coarse teeth as the standard teeth because the most common; so that you do not need to mark out. This point is metric only, the U.S. system products or to keep the tooth pitch.
Here focus on the specifications of the U.S. system screws, such as 6 #-32 * 3/8, 6 # is the outside diameter of the tooth, close to 3.5mm; 32 is the length of the thread per inch in 32 teeth (equivalent to the metric screw pitch); 3/8 is the length of the screw (precisely the same as the metric screw).
Here are 2 formulas to remember: The outside diameter of the tooth A# = (Ax0.013+0.06) x 25.4 (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. In addition, the number of teeth corresponding to each specification of the screw must also be familiar with: 2#-56, 4#-40, 6#-32, 8#-32, 10#-24, 1/4-20, 5/16-18, 3/8-16, 1/2-13 (U.S. standard teeth).
Note: US-made UNC teeth are standard teeth, UNF are fine teeth. We take coarse teeth as regular teeth by default.
Materials are the most common: carbon steel, stainless steel, stainless steel, copper, aluminium, 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).
General C1008 material is playing ordinary grade products, such as 4.8-grade screws, regular grade nuts; C1015 general play hanging ring screws; C1018 general do machine screws, of course, there are also used to do self-tapping nails; C1022 general used to do self-tapping nails; C1035 play 8.8-grade screws; C1045/10B21/40Cr play 10.9-grade screws; 40Cr/ SCM435 to play 12.9-grade screws.
Stainless steel has SS302/SS304/SS316 as the most common. But, of course, it is also popular now a large number of SS201 products, or even lower nickel content, we call the non-authentic stainless steel products; appearance looks similar to stainless steel, but the anti-corrosion performance is much different.
4,Strength grade of fastener
Strength grade mainly refers to the carbon steel class fasteners.
The standard strength grade of carbon steel screws is 4.8, 5.8, 6.8, 8.8, 10.9, 12.9. Nuts are correspondingly available: grade 4, grade 6, grade 8, grade 10, grade 12.
Generally, screws below grade 8.8 are called ordinary screws, while above grade 8.8 (including grade 8.8) are high-strength screws. The difference is that high-strength screws are required to go through the tempering heat treatment.
5,Surface treatment of Fastener
Surface treatment mainly increases the anti-corrosion properties, but also partly takes into account the colour, so mainly for carbon steel products, generally need to go through surface treatment.
Common surface treatments are blackening, galvanizing, copper plating, nickel plating, chromium plating, silver plating, gold plating, Dacromet, hot-dip zinc, etc.
There are many types of zinc plating, including blue and white zinc, blue zinc, white zinc, yellow zinc, black zinc, green zinc, etc., and also divided into environmental protection and non-environmental protection. Each plating has a variety of plating thickness to meet different salt spray test effects.
1. Bolts
A type of fastener consists of two parts: a head and a screw (a cylinder with external threads), which is used to fasten two parts with a through-hole in conjunction with a nut. This form of connection is called bolt connection. If the nut is screwed down from the bolt, the two parts can be separated, so the bolt connection is removable.
2. Stud
There is no head, only a class of fasteners with external threads on both ends. When connected, one end must be screwed into the parts with internally threaded holes, the other end through the details with through holes, and then screwed on the nut, even if the two parts are fastened and connected into a whole. This type of connection is called a stud connection and is also a removable connection. Mainly used for one of the thicknesses of the connected part is significant, requires a compact structure, or because of frequent disassembly, should not be used for bolting occasions.
3. Screw
It is also a class of fasteners consisting of two parts: head and screw, and can be divided into three categories according to the use: machine screws, set screws and special-purpose screws. Machine screws are mainly used for fastening threaded hole parts, and a fastening connection between parts with a through-hole, without the need for a nut fit (this form of connection is called screw connection, also belongs to the removable connection; can also be used with a nut fit, for fastening connection between two parts with a through-hole. Fastening screws are mainly used to fix the relative position between two components. Special purpose screws, such as lifting ring screws, are used for lifting parts.
4. Nuts
With an internally threaded hole, the shape is generally shown as a flat hexagonal column. It is also a flat square column or flat cylindrical, with bolts, studs or machine screws, used to fasten the connection of two parts so that it becomes a whole.
Similar to machine screws, but the thread on the screw is a particular thread for self-tapping screws. Used to fasten the connection of two thin metal components, making it a whole, the components need to make small holes in advance, due to the high hardness of this screw, can be directly screwed into the recesses of the details so that the components to form a response to the internal thread.
6. Wood screws
Also similar to machine screws, the thread on the screw is a particular thread for wood screws, which can be screwed directly into the wood component (or parts), used to connect a metal (or non-metal) part with a through-hole to a wood component fastened together. This connection is also removable.
7. Washer
The shape of a flat ring-shaped class of fasteners. Placed in the bolt, screw or nut support surface and connected parts between the surface, playing a role in increasing the contact surface area of the corresponding elements, reducing the pressure per unit area and protecting the surface of the related parts from damage; another type of elastic washer, but also to prevent the role of the nut back loose.
8. Retaining ring
For installation, equipment, shaft groove, or hole groove play a role in preventing the shaft or hole on the parts to move around.
9. Pin
Mainly for parts positioning, some can also be used for parts connection, fixed amounts, power transmission or lock other fasteners.
10. Rivet
A type of fastener consisting of two parts, the head and the nail bar, is used to fasten the connection of two parts (or components) through holes so that it becomes a whole. This connection form is called riveted connection, referred to as riveted. It is a non-removable connection. Because to make the two parts connected, the rivets on the parts must be broken.
11. Combination parts and connection sub
Combination parts refer to a combination of the supply of a class of fasteners, such as a machine screw (or bolt, since the supply of screws) and flat washers (or spring washers, lock washers) combined supply; connection vice refers to a particular bolt, nut and washer combination supply of a class of fasteners.
12. Welding nail
Due to the light and nail head (or no nail head) constitutes a different type of fasteners, with welding methods to connect him fixed in a part (or member) above, to then connect with other factors.
13. Steel wire bushing
Steel wire sleeve is a new type of threaded connection component made of high-strength, high-precision corrosion-resistant diamond-shaped wire refined. Shaped like a spring, installed in a specific screw hole of the substrate, its inner surface forms a standard thread, and when cooperating with screws (bolts), it can significantly improve the strength and wear resistance of the threaded connection; especially in aluminium, magnesium, cast iron, plastic and other low strength materials. Locking type is to add one or several turns of locking ring based on the standard type.
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