What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Nuts and bolts are one of the most widely used fasteners in modern mechanical structures. At present, the common metric bolts and nuts are generally trapezoidal in cross-section. The connection between the bolt and the nut is prone to loosening under severe vibration, or even falls off by itself, and the tightening force of the bolt and nut thread is mainly concentrated in the bolt thread and Between the teeth of the first few threads where the threads of the nut are in contact, resulting in loosening of the fastener and sliding pressure of the threads
In the automobile industry, it is often necessary to install bolts at the opening of a closed cavity to fix and connect other parts. However, the diameter of the opening of the closed cavity is often larger than that of the head of the bolt, so it is necessary to set a strip-shaped spacer on the head of the bolt, so that the spacer can penetrate the opening longitudinally, and then block the opening horizontally, so as to be stuck with an upside-down buckle. Bolt head. However, since the bolt body of the bolt has a certain length, the manual vertical and horizontal turning operation after the strip spacer penetrates the opening is very difficult, and it is easy to drop the bolt and the spacer into the airtight cavity together, which greatly increases the assembly time. Increased labor costs.
Sometimes, the iron screws are often seen broken, and sometimes, the stainless steel screws are also seen broken. But generally speaking, stainless steel screws rarely break. Because the stainless steel screw wire itself is relatively hard. But under certain circumstances, stainless steel screws can still break. So what are the main reasons for stainless steel screws to break? The reasons for the fracture of stainless steel screws are as follows: 1. The quality of raw materials used for stainless steel screws is poor, and the quality of stainless steel screws is not good. There are many impurities, impure, resulting in insufficient hardness of stainless steel screws. 2. The production process of stainless steel screws. For example, stainless steel screws with eccentric head and eccentricity, and the Q value is too deep and the R position design is too small during the down punching operation during production. 3. The customer uses too much force when using stainless steel screws. Generally, you do a torque test to see how much the minimum breaking force is, and then adjust the torque. Of course, stainless steel screws must be broken for more than three reasons. But the above three reasons are the main reasons for the fracture of stainless steel screws. When the stainless steel screw is found to be broken, it can be checked step by step. Find out what's causing it.
The first is to use two identical nuts to screw on the same bolt, and add a tightening torque between the two nuts to make the bolt connection reliable. The second is a special anti-loosening nut, which needs to be used together with a kind of anti-loosening washer. The special lock nut is not a hexagonal nut, but a medium round nut. There are 3, 4, 6 or 8 notches on the circumference of the nut (depending on the size of the nut and the product series of the manufacturer). Several notches are both the focal point of the tightening tool and the snap-in of the lock washer bayonet. The third type is to drill through threaded holes from the outer surface of the nut to the inner thread surface (usually 2, which are distributed at 90 on the outer surface), which are used to screw in small-diameter countersunk head screws. The purpose is to give the thread Apply a centripetal force to prevent the locknut from loosening. The better quality lock nut sold on the market is inlaid with a small copper block that is consistent with the thread of the lock nut on the inner surface of the nut to prevent the radial jacking screw from directly contacting the locked thread and damaging the latter. . This kind of lock nut is gradually applied in the shaft end locking of rotating motion parts, such as the anti-looseness of the bearing at the mounting end of the ball screw. The fourth type of lock nut is composed of two parts, each part has staggered cams. Since the slope angle of the internal wedge design is greater than the nut angle of the bolt, this combination is tightly integrated into a whole. When vibration occurs When the lock nut is moved, the raised parts of the lock nut move with each other to generate lifting tension, so as to achieve a perfect anti-loosening effect. The fifth is structural anti-loosening. Through the design and improvement of the threaded structure, a self-locking function is obtained without the help of other external factors. Therefore, its applicability is wider than the above methods, and the requirements for the environment are also relatively high. Low. There are many types of lock nuts, such as nylon nuts and flange nuts. In short, this kind of lock nuts plays a role in preventing loosening. Twist the nut onto the screw, screw, bolt, etc., so that it will not come loose. So that they can be actively connected together, so that it is firm, and the stability can reach a high degree.
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