What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
An embodiment of Guangdong Yueluo Hardware Industry Co., Ltd. provides a screw slotting device, as shown in Figure 1, which includes a workbench 1, a vibrating plate 2 is arranged on the upper part of the workbench 1, and a conveying device 3 is arranged on the vibrating plate 2. Below the discharge port, the slotting device 4 is arranged on one side of the conveying device 3, and the slotting device 4 is provided with a reciprocating cutting wheel 42 that can slot the screws in the conveying device 3 when it extends out. The device 4 is also fixedly provided with a fixed wheel 48 for grinding the grooved screws. Using the screw slotting device, the screws can be automatically sorted by the vibrating plate 2, which improves the production efficiency. The reciprocating motion of the cutting wheel 42 can greatly reduce the probability of knife breakage. Sanding, fixes burrs and roughness.
(1) The screw-in performance test is to screw the self-tapping locking screw sample into the test plate until one complete thread completely passes the test without breaking. (2) The destructive torque test is to clamp the stem of the self-tapping locking screw specimen in a thread mold or other device that matches the screw thread, and uses a calibrated torque-measuring device to measure the screw. Torque is applied until fracture, which should not occur in the clamped threaded portion. (3) Carry out a tensile test on the screw sample to check the minimum tensile load for failure. The fracture should be within the length of the rod or the unthreaded thread, and should not occur at the junction of the nail head and the rod. Before the sample breaks, it should be It can reach the minimum tensile load specified by the corresponding performance class. (4) Hydrogen embrittlement is a problem that must be strictly paid attention to in the surface treatment process of self-tapping locking screws. In the pickling process, the screw is stirred in dilute hydrochloric acid, and the amount of hydrogen absorbed by the pickling steel increases linearly with the square root of time and reaches the saturation value. Less than 100%, a large number of hydrogen atoms will be produced, which will be attached to the surface of the screw, resulting in hydrogen infiltration, and the steel will become brittle due to the absorption of hydrogen. The self-tapping locking screw takes 6~8h to drive hydrogen, and the temperature is 160~200℃ (phosphating) and 200~240℃ (electroplating). However, in the production process, the hydrogen drive time should be determined according to many production conditions such as core hardness, surface roughness, electroplating time, coating thickness, pickling time, and acid concentration. It is best to do it before passivation and just after electroplating.
hand screw is a screw with a plastic head, and the user fixes the hand screw by turning the plastic head by hand. At present, a hand screw is disclosed in the market publication number CN202203253U, which includes a plastic head and a screw rod, the plastic head and the screw rod are connected together, and the height of the plastic head is higher than that of an ordinary screw, and the height is 12 cm. The screw of the hand screw is fixed in the plastic head by glue. After a period of use, the aging of the glue leads to the loosening of the screw and the plastic head. When the plastic head is stressed, the screw rod comes out of the plastic head, which affects the normal use of the hand screw.
Type 1 nut refers to an ordinary hexagonal nut with a nominal height of m ≥ 0.8D. Its type and size should meet the requirements of GB/T6170; while the height of type 2 nut is higher than that of type 1 nut, its type and size should comply with GB/T6170. T6175. There are two purposes to increase the type 2 nut: one is to obtain a relatively inexpensive nut that does not require heat treatment by increasing the height of the nut. Because D≤M16 grade 8 type 1 nuts do not need heat treatment, among grade 8 nuts, only the specifications of D>M16~39 use type 2 nuts. Obviously, type 1 nuts that do not need heat treatment cannot reach grade 9 nuts. Mechanical property requirements. Another purpose of specifying Type 2 nuts is to obtain a more ductile grade 12 nut. As the height of the nut increases, the guaranteed stress index can be achieved at a lower quenching and tempering hardness, so the toughness of the nut is increased. Classified by tooth spacing: standard teeth, regular teeth, fine teeth, very fine teeth and cross teeth. Classification by material: stainless steel hexagon nuts and carbon steel hexagon nuts, copper hexagon nuts, iron hexagon nuts. Classification by thickness: hexagonal thick nuts and hexagonal thin nuts. Classification by usage: hot melt copper nut, hot pressed copper nut, embedded copper nut and ultrasonic copper nut
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