What Is a Pocket Screw?
The screw is a tool that uses the physical and mathematical principles of the circular rotation and friction of the bevel of the object to gradually tighten the objects and parts. Screw is a common term for fasteners, spoken daily. Screws are an indispensable industrial necessity in daily life: extremely small screws used in cameras, glasses, clocks, electronics, etc .; general screws for televisions, electrical products, musical instruments, furniture, etc .; as for engineering, architecture, bridges, large Screws and nuts; transportation equipment, airplanes, trams, cars, etc. are large and small screws. Screws have important tasks in industry. As long as there is industry on the earth, the function of screws is always important. The screw is a common invention in people's production and life for thousands of years. According to the field of application, it is the first invention of mankind.
- [luó s]
- The screw is a circular rotation using the bevel of the object and
- Screw, some people call it "
- The first person to describe the spiral was the Greek scientist Archimedes (ca. 287 BC-212 BC). The Archimedes spiral is a huge spiral in a wooden cylinder that is used to lift water from one level to another and irrigate the field. The real inventor may not be Archimedes himself. Maybe he just described something that already existed. Maybe it was designed by artisans of ancient Egypt to use irrigation on both sides of the Nile.
- In the Middle Ages, carpenters used wooden or metal nails to connect furniture with wooden structures. In the 16th century, nailmakers began to produce spiral-shaped nails, which could connect things more securely. That was a small step from this type of nail to a screw.
- Around 1550, the earliest metal nuts and bolts used as fasteners in Europe were made by hand on a simple wooden lathe.
- A: Metric screws B: American screws C: Imperial screws
- A: Metric Machine Screw: Metric
- Ex: M3 x 6 PPB: M3 machine screw, 6mm long, cross, round flat head, black plated.
- Finish Code: appearance treatment specifications
- Head Code: The shape of the head.
- Screw head shape. Cylindrical head. Half head. Sink down. Spherical cylindrical head. Pan head. Round head. Hex Head.
- The main purpose is to make the industrial products form a fixed body. In use, it often occurs that the teeth cannot be closely adhered to each other, the screw head is disconnected if it is tightened too hard, or the tooth pattern is not locked properly. Precision issues. Screws are "quantity products", not hand-made works of art. In mass production, the purpose is to provide consumers with high-precision and stable quality and popular prices. The accuracy of the screw is usually 6g (level 2, American standard "IFI" is 2A teeth), and the rough screw for construction engineering is 8g (level 3, "IFI" is 1A teeth). The value of screws is very important. In the world, there are examples of bankruptcy of automobile factories due to poor screw quality; there are also examples of aircraft crashes and vehicle overturns due to poor screw quality.
- Common screw types
- A: Machine Screw:
- The main classifications include ordinary screws, machine screws,
- 1. First remove the mud on the surface of the broken screw. Use the center to stab the center of the section and then use a drill to install a drill with a diameter of 6-8 mm. After drilling the hole, remove the small drill bit and replace it with a 16 mm diameter drill bit. Continue to expand and drill through the hole of the broken bolt.
- 2. Take a welding electrode with a diameter of less than 3.2 mm and use a small and medium current to cut the half of the bolt's entire length from the inside to the outside of the bore of the broken bolt. The start of the overlay should not be too long. In order to avoid burning through the outer wall of the broken bolt. After surfacing to the upper end of the broken bolt, surfacing welding continues to produce a cylinder with a diameter of 14-16 mm and a height of 8-10 mm.
- 3. After surfacing, hammer the end surface with a hand hammer to make the broken bolt vibrate in its axial direction. Due to the heat generated by the previous arc and the subsequent cooling plus the vibration at this time, the broken bolt and the thread of the body will be broken. Looseness occurs.
- 4. Carefully observe that when a small amount of rust leaks from the fracture after striking, you can take the M18 nut on the surfacing stigma and weld the two together.
- 5. Slightly cool after welding, use a plum wrench on the nut to twist left and right, or twist it back and forth while hitting the end face of the nut with a small hammer so that the broken bolt can be removed.
- 6. After removing the broken bolts, use a suitable tap to process the wire fasteners in the machine frame to remove rust and other debris in the holes.
Screw inspection method
- There are two types of screw surface inspections. One is inspection before the screws are produced without plating, and the other is inspection after the screws have been plated. That is, after the screws are hardened, the screws are surface-treated. After the screws are produced and before plating, we inspect the screws in terms of dimensions, tolerances and other aspects. See if it meets national standards or customer requirements. After the surface of the screw is treated, the screws we plated are inspected, mainly to check the color of the plating and whether there are any bad screws. In this way, when we send the screw to the customer, the customer can pass the customs smoothly. Inspection after screwing:
- I. Appearance quality requirements
- The appearance of screws is inspected from various aspects such as appearance and plating.
- Second, the inspection of the thickness of the screw coating
- 1.Gage method
- The amount used has a micrometer, vernier caliper, plug gauge, etc.
- 2.Magnetic method
- The magnetic method for measuring the thickness of a coating layer is a non-destructive measurement of a non-magnetic coating layer on a magnetic substrate with a magnetic thickness gauge.
- 3.Microscopy
- The microscope method is called metallographic method. It is to enlarge the etched fastener on a metallographic microscope with a micrometer eyepiece to measure the thickness of the coating on the section.
- 4.Timed flow method
- The timed flow method is to inject a solution capable of dissolving the plating layer on the local surface of the plating layer, and calculate the thickness of the plating layer according to the time required for the local plating layer to be dissolved. There are plating method, anodic dissolution Coulomb method and so on.
- Third, the inspection of the adhesion strength of the screw coating
- There are many methods to evaluate the adhesion between the coating and the base metal, and there are usually the following.
- 1. Friction polishing test; 2. File method test; 3. Scratch method; 4. Bending test; 5. Thermal shock test; 6. Extrusion method.
- Fourth, the corrosion resistance of screw plating
- The test methods for corrosion resistance of coatings are: atmospheric exposure test; neutral salt spray test (NSS test); acetate salt spray test (ASS test); copper accelerated acetate spray test (CASS test); and corrosion paste corrosion test (CORR test) and solution drip corrosion test; immersion test, immersion corrosion test, etc.
Application range of screws
- There are many names for screws. Everyone's name may be different. Some people call them screws, some call screws, some call standard parts, and some call fasteners. Although there are so many names, they all have the same meaning, all screws. Screw is a common term for fasteners. The principle of the screw is to use the physics and mathematical principles of the circular rotation and friction of the bevel of the object to gradually and gradually tighten the tool and the tool.
- Screws are indispensable in daily life and industrial production. Screws are also called industrial rice. It can be seen that screws are widely used. The scope of application of screws is: electronic products, mechanical products, digital products, power equipment, electromechanical products. Screws are also useful in ships, vehicles, hydraulic engineering, and even chemical experiments. Anyway, screws are used in many places. Such as the precision screws used in digital products. DVD, miniature screws for cameras, glasses, clocks, electronics, etc .; general screws for televisions, electrical products, musical instruments, furniture, etc .; as for engineering, construction, bridges, large screws, nuts; transportation equipment, aircraft, trams, automobiles Use the same size screws. Screws have important tasks in industry. As long as there is industry on the earth, the function of screws is always important.
- There are many types of screws, whether they are very small screws for glasses or large screws for large heavy electrical engineering. The accuracy of the screw is usually 6g (level 2, the American standard "IFI" is 2A teeth), and the rough screw for construction engineering is 1g.
- The use of screws is so extensive, so the screw market must be relatively large, and the demand must be relatively huge, and there must be more screw manufacturers in the screw industry. When choosing a professional screw purchaser, buyers must first understand some professional basic knowledge of screws, such as screw classification standards and American screw specifications.
Performance of screws
- If we are going to use a screw, then the first thing we need to do is to understand the performance of this screw , which is its characteristics, so that we can use the screw in the most correct place. Because there are many types of screws, the performance of each of these screws is different, so the screws have different uses. In order to prevent us from using the screw incorrectly, we must have a certain understanding of the performance of the screw, so that we can use the screw in the most correct place.
First of all, let's take a look at self-tapping screws. For self-tapping screws, there are 0.8mm to 12mm self-tapping screws. Generally, these screws have a high hardness. Self-tapping screws are subject to a screw-in test, that is, the screws are screwed into a test version, and then the hardness of the screws meets the standards. If they do not meet the standards, they need to be analyzed. Where is the problem? In order to find a solution.
Another type is the tail screw . As the name implies, the tail of the screw generally shows the shape of the tail. The hardness of this screw is also very strong. Compared with ordinary screws, it not only maintains a better ability, but also has a better ability to connect objects. The aspect effect is also very strong. Generally, for this type of screw, auxiliary processing is not required. You can directly drill a hole on the object to lock the object. Not only is it very convenient to use, but it can also greatly improve the work. effectiveness. This drilling screw is the first choice for workers in various fields.
From the above we can find that when we use screws, it is very important to understand the performance of various screws .
Screw anti-corrosion technology
- Stainless steel screws are made of metal, and there are four main methods for metal corrosion protection, namely the nature of the material, the environment in which it is used, the interface between the data and the environment, and the design to improve the metal structure. Unless there is a special need, it is not practical in terms of economic concepts, or it is difficult to completely isolate the appearance of the screw from the environmental elements that will cause corrosion, which may not be feasible in practice. Improving the design of the metal structure can improve the impact of special circumstances under certain conditions, but the design of most stainless steel screws cannot be fully modified, and its maintenance effect is not eternal. Therefore, this method cannot basically deal with the problem. Corrosion protection, that is, the appearance of anti-corrosion treatment is the most widely used method.
- Stainless steel screw surface anti-corrosion treatment refers to the application of various methods to apply a maintenance layer on the metal surface. Its role is to isolate the metal from the corrosive environment to prevent the corrosion process from occurring or to reduce the contact between the corrosive medium and the metal surface. The purpose of avoiding or mitigating corrosion.
- The maintenance layer shall be able to meet the following requests:
- 1.Corrosion resistance, wear resistance, high hardness,
- 2. Tight structure, intact, and small pores.
- 3. Strong separation and good adhesion from the base metal.
- 4. Spread evenly and have a certain thickness.
- The maintenance layer is usually divided into two types: metal coating and non-metal coating. Metal coating refers to the use of a metal or alloy with strong corrosion resistance to form a maintenance layer on the surface of easily corroded metals. This coating is also called plating. There are many methods and varieties for generating metal coatings, the most common of which is electroplating, followed by molten metal dip plating (hot dip plating) and chemical surface treatment. Non-metallic coating refers to the use of organic polymer materials such as paint and inorganic materials such as ceramics to form a maintenance layer on the surface of metal equipment or parts. This maintenance layer can completely isolate the base metal from the environmental medium and prevent the base metal from corrosion due to contact. Corrosion in stainless steel standard parts.
Moisture-proof measures for screws
- If the iron screw is wet, or if it is wet with liquid. It is very likely to get rusty if it is wet or wet. and so,