What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
As shown in FIG. 1 and FIG. 2 , a rivet die in the prior art includes a set of top die 1 and cover die 2 arranged opposite to each other. The top die 1 is provided with a cavity 1 in the center that matches the shape of the rivet dome head 3-1. -1, the center of the cover mold 2 is provided with a mold cavity 2-1 that matches the shape of the rivet dome head 3-3.
Guangdong Yueluo Hardware Industry Co., Ltd. discloses a telescopic screw. The main point of its technical solution is that it includes an upper screw rod, one end of the upper screw rod is provided with a screw head, and the other side of the upper screw rod opposite to the screw head is provided with a lower screw rod, and the lower screw rod is provided on the other side. A fixing rod is provided, a limiting hole is set on the fixing rod, a sliding rod is set on the upper screw rod, a limiting block matching the limiting hole is set on the sliding rod, and a cover plate is slidably sleeved on the sliding rod. An inner thread is arranged on the plate, a thread matching the inner thread is arranged on the fixing rod, an elastic member is sleeved on the fixing rod, and both ends of the elastic member are respectively in conflict with the upper screw rod and the lower screw rod. Guangdong Yueluo Hardware Industry Co., Ltd. telescopic screw is provided with a telescopic mechanism between the upper screw and the lower screw. Therefore, the screw can be suitable for threaded installation holes with the same diameter and different lengths, avoiding the screw being limited by the length of the threaded hole and unable to be installed.
The bolt performance grade label consists of two parts of numbers, which represent the nominal tensile strength value and yield ratio of the bolt material respectively. For example: a bolt with a performance level of 4.6, its meaning is: 1. The nominal tensile strength of the bolt material is 400MPa; 2. The yield ratio of the bolt material is 0.6; 3. The nominal yield strength of the bolt material is 400×0.6=240MPa Grade 10.9 high-strength bolts, after heat treatment, can reach: 1. The nominal tensile strength of the bolt material reaches 1000MPa; 2. The yield ratio of the bolt material is 0.9; 3. The nominal yield strength of the bolt material reaches 1000×0.9=900MPa class
1. The taper of the reaming hole should be 90°. It should be guaranteed that it should be less than 90° rather than greater than 90°. This is a key trick. 2. If the thickness of the sheet metal is less than the thickness of the head of the countersunk head screw, you can replace the screw with a smaller size, or it is better to ream a smaller hole instead of reaming the hole to increase the diameter of the bottom hole and cause the parts to not be pressed tightly. 3. If there are multiple countersunk head screw holes on the part, it should be processed more accurately. Once it is drilled crookedly, it will be ugly to assemble, but as long as the error is not large, it can be tightened completely, because when tightening, if the diameter of the screw is not very large. Large (about no more than 8mm), when there is an error in the hole distance, the screw head will be deformed due to the force when it is tightened or it will be tightened.
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