What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
1. Ordinary outer hexagon - widely used, characterized by relatively large tightening force, the disadvantage is that there must be enough operating space during installation, and adjustable wrench, open-end wrench or glasses wrench can be used during installation, all of the above wrenches require a large amount of space. operating space. 2. Cylindrical head hexagon socket - is the most widely used of all screws, because it has a relatively large tightening force, and can be operated with a hexagon wrench. It is very convenient to install and is used in almost all kinds of structures. The appearance is more beautiful and neat. The disadvantage is that the tightening force is slightly lower than the outer hexagon, and the inner hexagon is easily damaged due to repeated use and cannot be disassembled. 3. Pan head inner hexagon - rarely used mechanically, the mechanical properties are the same as above, mostly used in furniture, the main function is to increase the contact surface with wooden materials and increase the ornamental appearance. 4. Headless inner hexagon - must be used in certain structures, such as the top wire structure that requires a large top-tight force, or where the cylindrical head needs to be hidden. 5. Countersunk head hexagon - mostly used in power machinery, the main function is the same as the inner hexagon. 6. Nylon lock nut - a nylon rubber ring is embedded in the hexagonal surface to prevent the thread from loosening, and it is used on strong power machinery. 7. Flange nuts - mainly play the role of increasing the contact surface with the workpiece, mostly used in pipes, fasteners, some stamping parts and casting parts. 8. Ordinary hex nut - the most widely used and one of the most common fasteners.
Screw model Drive Code: groove on the head, 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, the outer diameter of the screw 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. Standard specification, usually not mentioned. A-2: Length Code: Screw length: For metric screws, the screw length is directly marked in mm. The total length of the screw is marked, only the length below the head is calculated, excluding the head height. But With the exception of flat head screws, the total length of the screw is marked with the head height. A-3: Drive Code/ Head Groove, Features.
Locating pins are widely used in mechanical equipment and automated assembly lines. There are many types of locating pins, including fixed locating pins, replaceable locating pins, tapered locating pins, edged locating pins, standard diamond locating pins, spring locating pins, etc. The function is to limit the free movement of parts and objects. Users often choose different positioning pins according to the actual conditions of the parts, for example, according to the occasion of use, requirements and performance, etc., to reasonably choose positioning pins of different shapes and performances. At present, users usually use a combination of cylindrical pins and edge-cutting positioning pins as the positioning method for gripper positioning methods in automatic line accompanying tooling and automatic grasping.
Common fastening screws include self-tapping screws, fine-pitch drywall screws, traditional wood screws, and fiberboard screws. The following are the characteristics of commonly used screws, everyone should choose them reasonably. Self-tapping screws The correct application of self-tapping screws should be used for the fastening and connection of metal materials with pre-drilled holes. It has the function of automatically tapping out the internal thread on the metal body, and can complete the thread engagement with it to play a tightening role. However, due to its high thread bottom diameter, when it is used in wood products, the cut into the wood will be shallower; and because the thread pitch is small, there is less wood structure between every two threads. Therefore, it is unreliable and unsafe to use self-tapping screws for wood mountings, especially loose wood. Drywall Screws The proper use of fine-pitch drywall screws is for fastening and joining between metal studs and plasterboard. It suffers from similar drawbacks as self-tapping screws when used on wood mountings. Moreover, due to the large diameter of the head of the dry-wall screw, the embedding of the head is poor, and it is easy to cause unevenness between the head of the screw and the surface of the mounting part after installation. Traditional wood screws Before using traditional wood screws, pre-drilling holes are required on the wooden mounting parts, otherwise it is easy to cause wood cracking. In addition, since the traditional wood screws are not heat-treated, the use of electric tools can easily cause the groove shape to be damaged, and manual installation is very laborious. Fiberboard screws are relatively new types of wood screws, suitable for power tool installation. However, due to its relatively simple thread design, it still cannot effectively solve the stubborn problem of easy cracking when used on hardwood, and it does not have any advantages in screwing speed and screwing torque. [2]
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