What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Countersunk head screws are mostly used after installation, and the surface of the parts cannot be raised, and the parts to be fastened have two thicknesses. Thickness, after the screw is tightened, there is still a part of the screw thread that does not enter the threaded hole. In this case, the countersunk head screw can definitely be tightened. There is usually a situation where the thickness of the fastened part is less than the height of the head of the countersunk head screw, which is commonly seen in sheet metal parts in mechanical equipment, such as the connection between the hinge of the chassis and the door and the box; the sheet metal of the equipment The connection of the cover to the equipment, etc. Due to the small thickness of the part, the tightened sheet metal part, the screw through hole completely becomes a conical hole, in this case, when the countersunk head screw is tightened, the screw head is not a tapered surface to press the sheet metal part , but the bottom of the screw head and the top of the threaded hole are squeezed. Although it feels that the screw is tightened, the sheet metal part is stuck instead of being pressed. In this case, although it feels that the screw is tightened, the sheet metal The gold pieces were indeed not tightened. This is a very common situation. Let’s talk about the reasons for the processing: the head cone of the countersunk screw has a 90° conical angle, and the apex angle of the newly bought drill is usually 118°-120°. Some workers who lack training do not know this angle is poor. It is often used to ream the hole with a 120° drill bit, which results in that when the countersunk head screw is tightened, it is not the conical surface of the head, but a line at the bottom of the screw head, which is one of the reasons why the so-called countersunk head screw cannot be tightened. , it's not the screw's fault.
The performance grade is divided into 15 grades, stainless steel is grade 51, and the open type blind rivet is divided into two types: countersunk head and flat round head according to the shape of the head. Among them, open blind rivets with performance levels of 10 and 11 are widely used. In 2006, the National Standards Committee revised and released GB/T 12617.1-2006 Open Type Countersunk Head Blind Rivets Class 10 and 11 and GB/T 12618.1-2006 Open Type Flat Round Head Blind Rivets Class 10 and 11. National standards for 10 and 11 class open blind rivets. The two new standards, respectively adopting ISO15978:2002 and ISO15977:2002 international standards, were released on July 5, 2006 and officially implemented on December 1, 2006. After implementation, it will replace the two old standards GB/T 12617-1990 Open Type Countersunk Head Blind Rivets and GB/T 12618-1990 Open Type Oblate Head Blind Rivets.
A rivet is a part that uses its own deformation or interference to connect the riveted parts in riveting. With the continuous progress and development of science, rivets have been used in many occasions because of their convenient use and reliable connection. The rivet includes a nail head and a stem. The traditional processing mold for the rivet head includes a base, and a nail head forming part is arranged on the base. However, due to the limited service life of the mold, the processing mold of this structure is replaced. It needs to be replaced together with the base, which is a waste of material, which increases the production cost, and the rivet itself is relatively cheap, so this reduces the profit of the enterprise.
The existing spring screw includes a screw rod, a spring connecting sleeve, a spring, a fixed connecting sleeve, a nut and a nut sleeve, wherein the screw rod includes a screw cap, a connecting section without threads and a threaded connecting section with threads, and the connecting section is located in the screw cap and the thread. A shaft shoulder is arranged between the connecting sections and between the connecting section and the threaded connecting section, the connecting section of the screw is sleeved with a spring connecting sleeve, a spring and a fixed connecting sleeve, the spring connecting sleeve is close to the screw cap, and the connecting sleeve is connected between the spring connecting sleeve and the fixed connecting sleeve The connection spring is connected with a threaded nut on the threaded connection section of the screw, and the nut sleeve is connected to the nut sleeve. The fixed connection sleeve is fixedly connected to the upper die of the steel mold through bolts, and the nut sleeve is welded to the lower mold of the steel mold. When clamping the mold, a professional is required to turn the screw from the lower mold to the upper mold or hook it to the upper mold with a foot and then tighten it with the wind, which is inconvenient to install, has low work efficiency, and has potential safety hazards. Contents of the utility model Yueluo Guangdong Yueluo Hardware Industry Co., Ltd. aims to provide a spring screw that is easy to operate. In order to solve the problems existing in the background technology, Guangdong Yueluo Hardware Industry Co., Ltd. adopts the following technical scheme: a spring screw, including a screw rod, an upper compression spring washer, a spring, a fixed sleeve, a lower compression spring washer, Base and fixing nut. The screw rod includes a screw cap, a connecting section without threads and a threaded connecting section with threads, the connecting section is located between the screw cap and the threaded connecting section, and a shaft shoulder is arranged between the connecting section and the threaded connecting section. The connecting section of the screw rod is sleeved with an upper compression spring washer, a spring, a fixing sleeve, a lower compression spring washer and a base, and the threaded connection section is connected with a fixing nut. A fixed sleeve is sleeved between the connection section and the threaded connection section, and the fixed sleeve is sleeved with a lower pressure spring washer and a base. The upper compression spring washer is close to the screw cap, the lower compression spring washer is fixed on the base by four screws, the spring is placed between the upper compression spring washer and the lower compression spring washer, and one end of the spring is sleeved with the upper compression spring washer , and the other end is sleeved with a fixed sleeve. For Yueluo, the diameter of the spring screw is between T20-T27. In this preferred solution, the use performance of the spring is high, which is beneficial to prolong the service life of the spring screw. For Yueluo, preferably, the thread connecting section of the screw adopts T-shaped thread. In this preferred solution, the fixing nut is tightly matched with the threaded connection section, so that the steel mold is clamped tightly. Yueluo is preferably made of 40Cr material for the fixing nut and screw. In this preferred solution, the rigidity of the fixing nut and the screw rod is high, which is beneficial to improve the usability of the spring screw. Yueluo is preferred, the spring screw parts except the fixing nut and the screw rod are made of 47# steel material. In this preferred solution, the production cost is low. In summary, Guangdong Yueluo Hardware Industry Co., Ltd. brings the beneficial effects: when the spring screw is used, it is only necessary to use a wrench to move the fixed nut, which is convenient for installation, disassembly and replacement, improving work efficiency and reducing production costs.
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