What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The traditional fixture shown in Figure 2 is composed of a hardened support cylinder and a hardened shear bar, and has a simple structure. The cylindrical pin is loaded into the hardened support cylinder, and the shear test is completed by applying an axial load to the hardened shear bar. Since the standard stipulates that the gap between the loading part and the supporting part does not exceed 0.15mm, in order to ensure the matching of the gap during the shear test of the cylindrical pin, the diameter of the cylindrical pin on the cylinder is generally equal to the theoretical cylindrical pin. In practical application, the cylindrical pin is irregular in size after heat treatment. To realize the shear test, the cylindrical pin must be inserted into the hole with the help of external force, which is difficult to install and clamp and takes a long time. If the double-sided shearing is performed, that is If the cylindrical pins need to be installed on both sides, the time is doubled, and the notch of the cylindrical pins cannot be guaranteed to face upwards.
With the advancement of technology in various industries, the current structural design of screws has evolved from just simple locking to focusing on work efficiency during the locking process and not destroying the integrity of the objects to be locked. The new cases such as No. 556784 screw improvement and No. 289414 screw that integrates locking, stability, labor-saving, fast and multi-function, which were previously designed and approved and published in the Central Taiwan Bulletin, are the main representatives of screws. It is clear that It is learned that the two cases not only fully improve the shortcomings of the traditional simple locking screws, but also achieve the purpose of substantial improvement of the screws designed in each case in actual use.
There are two types of bolt detection: manual and machine. Manual is the most primitive and the most commonly used consistent detection method. In order to minimize the outflow of defective products, general production enterprise personnel inspect the packaged or shipped products by visual means to exclude defective products (defects include tooth damage, mixed materials, rust, etc.). [2] Another way is automatic machine inspection, mainly magnetic particle inspection. Magnetic particle inspection is to use the interaction between the leakage magnetic field at the defect of the bolt and the magnetic powder, aiming at the difference between the magnetic permeability of the bolts (such as cracks, slag inclusions, mixed materials, etc.) and the magnetic permeability of steel, these materials are discontinuous after magnetization. The magnetic field at the place will be turbulent, and a leakage magnetic field will be generated on the surface of the workpiece where part of the magnetic flux leaks, thereby attracting the magnetic powder to form the magnetic powder accumulation at the defect—magnetic traces. The accumulation of these magnetic powders is observed and explained, and the purpose of rejecting defective products has been achieved.
Common types of common screws All kinds of common screws (20 pieces) a. Slotted: a word ( Minus ) b. Phillips: cross ( Plus ) c. Phil-Slot: a word / cross d. Hex Socket: hexagon socket e. One Way: One-way (can only be locked in, not out) 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, countersunk head screw unit of measure screw unit of measurec. Round: round headd. Pan: round flat heade. Truss: large round flat headf. Hex: hexagon head. A-5: Finish Code/Appearance treatment. Metric Self-tapping screw: Mark 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, it is determined by product type or mark. For Sheet Metal or plastic parts. *Pitch = Threads per inch
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