What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Some electronic products need to install some plastic parts or protective sleeves for components on the PCB, which need to be fixed by screws. The function of the fixture is to locate the PCB and the required installation parts, and increase the work efficiency. The existing screw fixture is inconvenient According to the needs of the site, the positioning station of the screw can be changed, the accurate positioning of the screw is difficult and the clamping effect of the workpiece is poor. A screw jig is proposed.
In the prior art, the independent pocketed spring is to encapsulate the springs in bags independently, connect each independent pocketed spring side by side, and then cover it with a large non-woven fabric to form a Spring cushions. This spring mat structure has many disadvantages: 1. Uneven force and low hardness; 2. Easy to deform, pit, low flatness and unsightly; 3. The spring directly contacts the non-woven fabric, causing wear and tear, and the life of the spring mat relatively short.
Round head three-combination screw The screw size in the round-head three-combination screw is GB818, and the main technical requirements of various types are: iron and stainless steel material requirements, iron low, medium, high carbon steel, stainless steel combination The materials of the screws are stainless steel 201, stainless steel 304 and stainless steel 316. The thread tolerance is 6G, and the mechanical properties of the iron combination screws are 4.8 and 8.8. The 4.8-level combination screws are ordinary steel, and the maximum allowable hardness is 255HV. The 8.8-level combination screws are generally made of wire rod 10B21. , and then undergo hardening treatment, and then dehydrogenation after hardening treatment. Hydrogen removal is to prevent hydrogen embrittlement of the spring washer in the combination screw. Prevent the spring pad from breaking. The tolerance class of the combination screws is A. The cross groove is H-shaped. The surface treatment of the combination screw has environmental protection and non-environmental protection. Such as, environmental protection blue zinc, environmental protection color zinc, black zinc, color zinc, white nickel and so on. The technical requirement of the combination screw for the spring washer is that the washer should be able to rotate automatically without falling off.
According to relevant standards, the performance grades of carbon steel and alloy steel bolts are divided into more than 10 grades such as 3.6, 4.6, 4.8, 5.6, 6.8, 8.8, 9.8, 10.9, 12.9, etc. Among them, the bolts of grade 8.8 and above are made of low-carbon alloy steel or medium Carbon steel and heat treatment (quenching, tempering) are generally called high-strength bolts, and the rest are generally called ordinary bolts. 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. Stainless steel bolts are divided into A1-50, A1-70, A1-80, A2-50, A2-70, A2-80, A3-50, A3-70, A3-80, A4-50, A4-70, A4-80, A5-50, A5-70, A5-80, C1-50, C1-70, C1-110, C4-50, C4-70, C3-80, F1-45, F1- 60. The first letter and number represent the stainless steel group, and the second and third numbers represent 1/10 of the tensile strength. [2]
The above content is uploaded by Yueluo or the Internet. If there is any copyright issue, please contact [email protected].
