What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
Commonly used standards are broadcast. For hexagonal nuts, the commonly used standards are: GB52, GB6170, GB6172 and DIN934. The main differences between them are: the thickness of GB6170 is thicker than that of GB52, GB6172 and DIN934, commonly known as thick screw cap. The other is the difference between the opposite sides, the opposite sides of DIN934, GB6170 and GB6172 in the M8 nut series are 13MM smaller than the opposite side 14MM of GB52, and the opposite sides of M10 nuts, DIN934 and GB52 are 17MM. The opposite side of GB6170 and GB6172 should be 1MM larger, M12 nut, DIN934, GB52's opposite side is 19MM larger than GB6170 and GB6172's opposite side 18MM is 1MM larger. For M14 nuts, the opposite side of DIN934 and GB52 is 22MM, which is 1MM larger than the opposite side of GB6170 and GB6172, which is 21MM. The other is the M22 nut. The opposite side of DIN934 and GB52 is 32MM, which is 2MM smaller than the opposite side of GB6170 and GB6172, which is 34MM. (Besides the thickness of GB6170 and GB6172 are the same, the width of the opposite side is exactly the same) The rest of the specifications can be used in general without considering the thickness.
There are two typical pin shearing fixture tooling, among which the traditional fixture shown in Fig. 1 is more complicated and consists of fixture, spacer, washer and shearing block guide post, hardened bushing, shearing block and so on. The cylindrical pin is installed in the hardened bushing, and the axial load is applied through the shear block to complete the shear test. The fixture is complicated in manufacture and has many consumables, because the size of the hardened bushing is similar to that of the cylindrical pin. , and to keep the notch of the cylindrical pin upward, it is difficult to install before the test, and the broken cylindrical pin after the test remains in the hardened bushing and is difficult to remove.
Thread Code Broadcast Coarse Thread Series UNC Fine Thread Series UNF Extra Fine Thread Series UNEF Fixed Pitch Series UN Marking Method Broadcast Marking Method: Thread Diameter - Number of Threads per Inch Serial Code - Accuracy Grade Example: Coarse Thread Series 3/8—16 UNC— 2A Fine pitch series 3/8—24 UNF—2A Extra fine pitch series 3/8—32 UNEF—2A Fixed pitch series 3/8—20 UN—2A The first digit 3/8 indicates the outer diameter of the thread, in inches , to convert to metric unit mm, multiply by 25.4, that is, 3/8×25.4=9.525mm; the second and third digits 16, 24, 32, 20 are the number of teeth per inch (the number of teeth on the 25.4mm length); The text code UNC, UNF, UNEF, UN after the third digit is the series code, and the last two digits 2A are the precision grade. UNC: Unified Coarse Thread.
With the continuous improvement of automation technology, human participation in the production process is gradually decreasing, especially in the processing of some small parts, the manual processing efficiency and accuracy are low. Whether the screws can be stably picked up and installed automatically is of great help to improve automated production.
The above content is uploaded by Yueluo or the Internet. If there is any copyright issue, please contact [email protected].
