About screws

time:2021-11-10 23:07:04    browse:2330

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Various screw thread types 

A: Triangular thread (60 degrees): Combination/locking 

B: Pipe triangular thread (55 degrees): Combination/locking 

C: Trapezoidal thread (30 or 29 degrees): Power transmission 

D: Square thread ( 90 degrees): power transmission

The value of screws

There are many types of screws, whether they are very small screws for eyeglasses or large screws for large-scale heavy electrical engineering. The main purpose is to use high-level industrial products to form a fixed unit. If it is often used, the teeth cannot be closely attached. , If you tighten too hard, the screw head will break off, or if the tooth pattern is bad and the lock is not tightened, it will not meet the conditions of use, which is a quality accuracy problem. Screws are "quantity products", not hand-made artworks. In mass production, the goal is to supply consumers with high-precision and stable quality and popular prices. The accuracy of screws is usually 6g (level 2, American standard "IFI" is 2A thread), and the rough screw used in construction engineering is 8g (level 3, "IFI" is 1A thread). This book provides reference for the technical key points of the manufacturing process of hexagonal head screws and general small head screws (iron plate screws, wood screws, machine screws).


A: Machine Screw:
B: Tapping Screw: ¡¡¡¡B-1: Sheet Metal Tapping Screw.¡¡B-2: Plastic Tapping Screw.¡¡¡¡C: Wooden Screw ¡¡¡¡D: Drywall Screw  ¡¡¡¡E: Self Drilling Screws

This product is suitable for 

1 stainless steel plate, metal steel plate, galvanized steel plate, and engineering installation.¡¡¡¡ 

2 Metal curtain wall, metal light partition, etc. indoor and outdoor installation.

3 General angle steel, channel steel, iron plate and other metal materials are combined and installed.

4. Assembling projects for automobile trunks, container boxes, shipbuilding, refrigeration equipment, etc.

Features of this product: ¡¡¡¡ 

1. Drilling and tapping, locking can be completed at one time, strong binding force.

 2. Save construction time and improve work efficiency.¡¡E-1:STAINLESS STEEL SELF DRILLING SCREWS ¡¡E-2:Bi-Metal Self Drilling Screws

a.Low Carbon Steel: Carbon steel Carbon steel is divided into low carbon steel, medium carbon steel, high carbon steel and alloy steel. 

b. SS-304: Stainless Steel 304 and 316 belong to stainless steel 

c. SS-302: Stainless Steel 302: better structural toughness d. Aluminum 5052: Aluminum alloy 5052 ¡¡¡¡ 

d. Brass: Brass 

e. Bronze: Bronze 

f . UNS C11000 Copper: Antimony Copper
 

Common screw specifications and markings
A: Metric screw screw
B: American standard screws 

C: British screws 

A: Metric machine screws: Metric ¡¡¡¡ Ex: M3 x 6 ¨C PPB: M3 machine screws, 6mm long, cross, flat head, black plated. 

Finish Code: Appearance processing specifications Head Code: Head Thread Code ¡¡¡¡ 

Screw Model Drive Code: Head section groove, Characteristic Model Length Code: Screw Length (mm) ¡¡¡¡A-1: Thread Code: Screw Model Metric screws directly indicate the screw model with the outer diameter of the screw, ¡¡¡¡ such as M3, that is outside the screw The diameter is 3.00mm.; M4 means the outer diameter of the screw is 4.00mm. ¡¡¡¡Metric Thread Size x Pitch:

Note: The metric screw is behind the screw model, and sometimes the screw pitch is indicated. ¡¡¡¡ Such as M3x0.5, M4x0.70, M5x0.8 , M6x1. ¡¡¡¡ But because of the standard specifications, it is usually not mentioned. ¡¡¡¡A-2: Length Code: Screw length: ¡¡¡¡ Metric screws, directly indicate the length of the screw, in mm. ¡¡¡¡ The total length of the screw is indicated, only the length below the head is counted, excluding Head height. ¡¡¡¡Except for flat head screws, the total length of the screw is indicated including the head height. ¡¡¡¡A-3: Drive Code/ Head section groove, characteristic.

 

Common specifications
a. Slotted: One character (Minus)

b. Phillips: Cross (Plus) various common screws (20 sheets) ¡¡¡¡ 

c. Phil-Slot: One character/cross 

d. Hex Scoket: Hex socket 

e. One Way: One way ( Can only be locked in, not exited) ¡¡¡¡A-4: Head Code/ head shape. ¡¡¡¡a. Flat: Flat head (after locking, the top is flush with the work piece) ¡¡¡¡b. Oval: Salad head, O head, semi-sunk head c. Round: Round head d. Pan: Round flat head e. Truss: Big round flat head f. Hex: Hex head. ¡¡¡¡A-5: Finish Code/ Appearance treatment. ¡¡¡¡ Metric self-tapping screw: Mark the Tapping Type directly behind the product name. Ex: M3 x 6 -PPB, Tapping Type: ¡¡¡¡ M3 self-tapping screw, 6mm long, cross, round flat head, black plated. ¡¡¡¡ generally use product type or label, and then judged as Sheet Metal or plastic parts. ¡¡¡¡***Thread is Number of teeth per inch.***

 

Screw length
The U.S. standard screw length must be converted to the metric system mm size. ¡¡¡¡ conversion formula: (Length Code / 32) x 25.40 = metric length mm ¡¡¡¡ B-3, B-4, B-5: The marking method is the same as the metric system.
Edit this paragraph inch screws

C-1: Thread Code: ¡¡¡¡ indicates that the denominator is 8, and then directly called the number of the numerator. ¡¡¡¡Ex: 1/8 x 0.50 ¨CPPB: 1 cent screw x 0.50¡± long, PPB ¡¡¡¡Ex: 5/16 x 0.50 ¨CPPB = 2.5/8 x 0.50-PPB: 2 half screw x 0.50" long, PPB ¡¡¡¡Ex: 5/32 x 0.50 ¨CPPB =1.25/8 x 0.50-PPB: 1 minute 2 half screw x 0.50" long, PPB Ex: 1/4 x 0.50-PPB= 2/8 x 0.50-PPB: 2-point screw x 0.50" long, PPB ¡¡¡¡ Note: Sometimes it may indicate coarse or fine teeth. ¡¡¡¡UNF: Fine teeth: more commonly used in the electronics industry. ¡¡¡¡UNC : Coarse thread: Heavy mechanical structure is more commonly used. ¡¡¡¡Ex: 3/8 x 0.50 ,UNF-PPB: 3 points fine screw x 0.50¡± long, PPB. ¡¡¡¡C-2: Length Code: ¡¡¡¡ is the inch mark, must be multiplied by 25.40 to convert¡¡¡¡ is measured with a buckle gauge. It is a metric thread that is consistent with a metric thread, and an inch thread is consistent with an inch thread. ¡¡¡¡ You can also use a caliper to measure the outer diameter and pitch of the thread. ¡¡¡¡ The outer diameter of the metric thread is in millimeters, such as 6 , 8, 10, 12, 18, 20 mm, etc. The pitch is also in millimeters, such as 0.5, 0.75, 1, 1.5, 2, 3, etc. The outer diameter of the inch thread is in inches, (each inch is equal to 25.4 Mm) such as 3/16, 5/8, 1/4, 1/2, etc. Therefore, the reading of the outer diameter with a metric caliper often has irregular decimals.

The imperial pitch is expressed by the number of teeth per inch. Set the caliper at 25.4 mm, align one ruler tip with the thread tip, and the other ruler tip should be an inch thread if it is aligned with the thread tip. If it is not aligned with the thread tip, it should be a metric thread.¡¡¡¡ When measuring the thread pitch, it is best to print the tip of the thread on the white chalk. The mark on the chalk is relatively clear and easy to measure. To measure the metric screw pitch, you should measure a length, such as 10, 15, 20, millimeters, etc., count how many teeth it contains, and calculate the pitch in inches. The thread specification is inch thread, such as: G1". The metric unit is specified in millimeters. The thread specification is metric thread. For example: M30. ¡¡¡¡The inch system is determined by how many teeth are in one inch (24.5 cm), generally 55 degrees. The metric system is the pitch of the two tooth tips, which is determined by the number of MM. 60 degree angle anchor screws: screws used to fasten machines on the ground. Also called anchor bolts. ¡¡¡¡ The difference between inch screws and American screws is difficult to distinguish by visual inspection. The difference between British and American screws lies in the twisting angle of inch screws It is 55 degrees, while the screw thread angle of the American screw is 60 degrees. These two standard screws can be used in most of the time, but the 1/2 specification screw is not available, because the standard thread of the inch 1/2 standard is 1 /2-12 teeth, while the US version is 1/2-13 teeth.
 

 

Screw classification
The main categories include ordinary screws, self-tapping screws and expansion screws.¡¡¡¡ Cap screw used to be limited to full-tooth fasteners, but this is not the standard usage now.¡¡¡¡ Hex cap screw and large hex bolt Hex bolt, as the name implies, are externally threaded fasteners with a hexagonal head, which are designed to be rotated by a wrench. According to the ASME B18.2.1 standard, the hexagon head screw (Hex cap screw) has a smaller head height and rod length tolerance than the general large hexagon bolt (Hex bolt). Therefore, the ASME B18.2.1 hexagon screw is suitable for installation on all hexagon bolts that can be used. Places, including places where large hexagon bolts are too large to be used. Socket cap screw, also known as socket cap screw or Allen bolt, is a screw with a hexagonal inner hole on the head. It can only be inserted into the inner hole with a hex key (Allen wrench or Allen key). Tighten or loosen. Hexagon socket screws are the most commonly used cylinder head screws, the head diameter is about 1.5 times the main diameter of the thread (1960 series), other head types include the Bottom head cap screw (bottom head cap screw) for beautiful surface and suitable for tapered screw holes Countersunk head cap screw (Countersunk head cap screw). The counterbore design allows the screw head to be able to rotate without being exposed on the surface of the fixed object, so it is mostly used in places where the surface is small and traditional wrenches are inconvenient to use.¡¡¡¡Machine screw is generally a screw (4#~12#) with a diameter less than ¼ inches (4#~12#), usually full thread and rotated by a screwdriver, such as slotted, cross or hexagon socket.


The value of screws Screws are indispensable industrial necessities in daily life: such as very small screws used in cameras, glasses, watches, electronics, etc.; general screws for televisions, electrical products, musical instruments, furniture, etc.; as for engineering, construction, and bridges Use large screws and nuts; transportation equipment, airplanes, trams, cars, etc., use both large and small screws. Screws have important tasks in industry. As long as there is industry on the earth, the function of screws will always be important. There are many types of screws, whether they are very small screws for eyeglasses or large screws for large-scale heavy electrical engineering. The main purpose is to use high-level industrial products to form a fixed unit. If it is often used, the teeth cannot be closely attached. , If you tighten too hard, the screw head will break off, or if the tooth pattern is bad and the lock is not tightened, it will not meet the conditions of use, which is a quality accuracy problem. Screws are "quantity products", not hand-made artworks. In mass production, the goal is to supply consumers with high-precision and stable quality and popular prices. The accuracy of screws is usually 6g (level 2, American standard "IFI" is 2A thread), and the rough screw used in construction engineering is 1g (level 3, "IFI" is 1A thread).

Screw use
1. First, remove the sludge on the surface of the broken screw and use the center blaster to kill the center of the section. Then use an electric drill to install a 6-8 mm diameter drill to drill the hole at the center of the section. Note that the hole must be drilled through. After the hole is drilled, remove the small drill bit and replace it with a drill bit with a diameter of 16 mm, and continue to enlarge and drill the hole of the broken bolt. 2. Take a welding rod with a diameter of less than 3.2 mm and use small and medium current to carry out surfacing from the inside to the outside of the hole of the broken bolt. Take half of the entire length of the bolt at the beginning of the surfacing. When starting the surfacing, do not start the arc too long So as not to burn through the outer wall of the broken bolt. After welding to the upper end of the broken bolt, continue to weld a cylinder with a diameter of 14-16 mm and a height of 8-10 mm. 3. After the surfacing is completed, hammer the end face with a hand hammer to cause the broken bolt to vibrate along its axial direction. Due to the heat generated by the arc before and the subsequent cooling plus the vibration at this time, the bolt and the thread of the body will be broken There is looseness between.¡¡¡¡4. Observe carefully. When it is found that there is a trace of rust leaking from the fracture after knocking, you can take the M18 nut and put it on the surfacing stigma and weld the two together.¡¡¡¡5. After welding, use a torx wrench to set the nut on the nut while it is still warm. You can also twist it back and forth while tapping the end face of the nut with a small hand hammer to take out the broken bolt.¡¡¡¡6. After taking out the broken bolts, use a suitable wire hammer to process the threads in the frame to remove the rust in the holes

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Dongguan Wenli Precision Hardware Co., Ltd.