When manufacturing combined screws and customers place orders for them, it's common to hear that the quality is just fine. But how can you actually assess whether the quality of a combined screw is good? Here's a brief introduction from the manufacturer of combined screws:
The quality of a combined screw starts with the wire used in its production. The screw wire is the first factor that determines the overall quality of the combined screw. If the wire is substandard, even with advanced machinery and skilled workers, it's impossible to produce high-quality combined screws.
Next, you can evaluate the quality by looking at the overall appearance of the combined screw. A well-made screw should have a properly sized head, a flat washer with a smooth surface, and threads that pass the stop gauge test. These are all important factors that need to be checked. A good combination screw should meet national or customer specifications in terms of size and finish.
Finally, the plating color is another indicator of quality. While iron-based combined screws typically require plating, stainless steel ones usually undergo passivation to improve their corrosion resistance. Poorly controlled plating can lead to uneven coloration, which affects the visual appeal of the product.
Key Points to Consider When Installing High-Strength Bolts
1. Quality Considerations
(1) Ensure that any rust, oil stains, burrs, or welding spatter on the bolt hole walls are thoroughly cleaned.
(2) After treating the friction surface, ensure it meets the required coefficient of friction. High-strength bolts must be used with matching nuts and washers.
(3) During installation, avoid contaminating the treated friction surface with oil, dirt, or other debris.
(4) Keep the friction surface dry during installation and avoid using it in rainy conditions.
(5) Before installation, carefully inspect and correct any deformation in the connected steel plates.
(6) Avoid hammering the bolt during installation to prevent thread damage.
(7) Regularly calibrate the electric wrench to ensure accurate torque and follow the proper tightening sequence.
2. Main Safety Measures
(1) Use an adjustable wrench that matches the nut size. Never use a small wrench with an extension. For high-altitude work, use a dead wrench, and if a spanner is needed, secure it with a rope.
(2) When assembling connecting bolts on steel components, never insert your hands into the connection area or the screw hole. When handling horn plates, keep your fingers on both sides of the plate.
Overview of Locknut Characteristics and Applications
A locknut is a fastening component used to securely connect mechanical equipment. It works by engaging with a screw of the same thread size. For example, an M4-0.7 nut only fits with an M4-0.7 screw (where "M4" refers to the inner diameter of about 4mm, and "0.7" indicates the distance between threads). Similarly, American products like a 1/4-20 nut only match with a 1/4-20 screw (with an inner diameter of approximately 0.25 inches and 20 threads per inch).
The DISC-LOCK locknut consists of two parts with staggered cam mechanisms. Its internal wedge design has a slope angle greater than the bolt’s nut angle, allowing it to grip tightly when vibration occurs. The convex parts of the locknut move against each other, creating tension and providing excellent anti-loosening performance.
Main Features: Easy to install; no need for washers; easy to disassemble and reusable; made from medium carbon steel; compatible with high-strength bolts like 8.8 and 10.9; tested under US military MIL-STD 1312 Vibration Test 7, Junker Test, and Dynamic Test.
Applications: Automotive (cars, trucks, buses), compressors, construction machinery, wind power equipment, agricultural machinery, foundries, drilling equipment, shipbuilding, military, mining equipment, oil rigs (onshore/offshore), public facilities, rail transit, transmission systems, metallurgical equipment, rock hammers.
Rivet Nut and Its Characteristics
A rivet nut, also known as a self-locking nut, is used for attaching thin sheets or sheet metal. It has a circular shape with embossed teeth and a guiding groove on one end. The principle involves pressing the embossed teeth into a pre-drilled hole in the sheet metal. The hole is slightly smaller than the rivet nut’s teeth, and when pressure is applied, the rivet nut is squeezed into the material. This causes plastic deformation around the hole, pushing the deformed material into the groove and creating a secure lock.
Rivet nuts come in different types, such as fast-cut steel S-type, stainless steel CLS-type, stainless steel SP-type, and copper or aluminum CLA-type, each suitable for specific environments. They are commonly available in sizes from M2 to M12. There is no unified national standard for rivet nuts, but they are widely used in chassis cabinets and sheet metal applications.
Difference Between Screws and Bolts
Screws and bolts serve different purposes. Screws are typically used to fasten fixed parts and are designed for easy installation and removal. Their strength is generally lower than that of bolts. Bolts, on the other hand, are stronger and often used in load-bearing applications, where they can withstand significant forces. A well-designed system allows bolts to handle tension or compression without being subjected to shear forces.
In most cases, screws are threaded directly into a part’s threaded hole and rarely used with nuts. Bolts, however, are usually tightened with a nut and less frequently used in threaded holes. Of course, there are exceptions, and unconventional usage isn't always wrong, but it should be done with care and flexibility.
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