What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
(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.
In another embodiment of Guangdong Yueluo Hardware Industry Co., Ltd., the slotting device 4 includes a motor 41 and a motor 43, the cutting wheel 42 is fixedly arranged at the output end of the motor 41, and the motor 41 drives the cutting wheel 42 to rotate to open the screw. slot, the motor 43 is fixedly arranged on the workbench 1, the motor 41 is arranged on the motor 43, a track 47 is arranged between the motor 41 and the motor 43, the motor 41 can reciprocate through the track 47, and when the screw is slotted, the motor 41 drives the cutting wheel 42 to move in the direction of the screw. When the slotting is finished, the motor 41 drives the cutting wheel 42 to retract. The fixed wheel 48 is arranged at the output end of the motor 43. The fixed wheel 48 is located directly below the cutting wheel 42. The surface of the middle screw is in contact, and the motor 43 drives the fixed wheel 48 to rotate to grind and polish the surface of the slotted screw to make the surface smooth. Preferably, the direction of rotation of the cutting wheel 42 and the fixed wheel 57 is opposite.
The quality of electroplating is measured primarily by its corrosion resistance, followed by appearance. Corrosion resistance is to imitate the working environment of the product, set it as the test condition, and perform a corrosion test on it. The quality of electroplating products shall be controlled from the following aspects: 1. Appearance: Partial uncoated, scorched, rough, gray, peeling, crusted, and obvious stripes are not allowed on the surface of the product, and pinholes, pitting, and black plating are not allowed. Slag, loose passivation film, cracks, peeling off and serious passivation marks. 2. Coating thickness: The operating life of fasteners in corrosive atmosphere is proportional to its coating thickness. The general recommended thickness of economical electroplating coating is 0.00015in ~ 0.0005in (4 ~ 12um). Hot-dip galvanizing: the standard average thickness is 54 um (43 um for diameter ≤ 3/8), and the minimum thickness is 43 um (37 um for diameter ≤ 3/8). 3. Coating distribution: With different deposition methods, the aggregation method of the coating on the surface of the fastener is also different. During electroplating, the coating metal is not uniformly deposited on the peripheral edge, and a thicker coating is obtained at the corners. In the threaded portion of the fastener, the thickest coating is located on the thread crest, gradually thinning along the flank of the thread, and the thinnest deposit is at the bottom of the thread, while hot dip galvanizing is just the opposite, the thicker coating is deposited on the inside corners and On the bottom of the thread, mechanical plating tends to deposit the same metal as hot-dip plating, but is smoother and has a much more uniform thickness over the entire surface [3]. 4. Hydrogen embrittlement: During the processing and processing of fasteners, especially in the pickling and alkali washing before plating and the subsequent electroplating process, the surface absorbs hydrogen atoms, and the deposited metal coating then traps hydrogen. When the fastener is tightened, the hydrogen is transferred towards the most stressed parts, causing the pressure to build up beyond the strength of the base metal and producing microscopic surface cracks. Hydrogen is particularly active and quickly seeps into the newly formed fissures. This pressure-rupture-penetration cycle continues until the fastener breaks. Usually occurs within a few hours after the first stress application. To eliminate the threat of hydrogen embrittlement, fasteners are heated and baked as soon as possible after plating to allow hydrogen to seep out of the plating, typically at 375-4000F (176-190C) for 3-24 hours. Since mechanical galvanizing is non-electrolyte, this virtually eliminates the threat of hydrogen embrittlement, which exists in galvanizing using electrochemical methods. In addition, due to engineering standards, it is forbidden to hot-dip galvanize fasteners with hardness higher than HRC35 (Imperial Gr8, metric 10.9 and above). Therefore, hydrogen embrittlement rarely occurs in hot-dip plated fasteners. 5. Adhesion: Cut or pry off with a solid tip and considerable pressure. If, in front of the blade tip, the coating peels off in flakes or skins, exposing the base metal, the adhesion shall be considered insufficient.
Gaskets are widely used in the machinery industry. According to the different needs of machinery and equipment in different industries, the structural forms of the sealing points are also different. Plum washer is one of the commonly used seals. It is commonly used between the pump and the motor coupling. In the actual production process of the enterprise, it is found that due to the influence of the material and structure, this type of gasket in common use can withstand impact force. Small, the septum is easily damaged. Because the current plum washers are all one-piece structures, even if one or several of the partitions are damaged, they need to be replaced as a whole. Although the value of a single plum washer is low, it needs to be shut down for maintenance and replacement almost every week. It also seriously affects the normal production of the enterprise, and the one-piece plum blossom gasket is also difficult to repair, adding unnecessary use costs to the enterprise. For this reason, the plum blossom gasket needs to be improved to strengthen the impact resistance of the gasket, and can be repeated Maintenance and use, prolong the maintenance cycle of the equipment, and ensure the normal production of the enterprise. The purpose of the utility model Yueluo is to solve the above-mentioned deficiencies in the existing technology, improve the existing technology, and provide a simple structure, which strengthens the impact resistance of the gasket, and can be repeatedly maintained and used to prolong the maintenance of the equipment. The cycle guarantees the plum blossom elastic washer normally produced by the enterprise. In order to achieve the above purpose, Yueluo is achieved through the following technical solutions-namely a plum blossom elastic washer, including an elastic washer body with a partition, the technical point is that the washer body is composed of a washer base and a partition that is independent of each other. , the septum and the gasket base are fixedly connected into one through the fixing piece. In order to further strengthen the impact resistance of Yueluo, the contact parts of the spacer and the washer base are respectively processed with a limited clamping table and a matching groove, so that the spacer and the washer base can be better integrated into one. According to the different specifications of the torx washer, the spacer and the washer can be fixed as a whole by rivets; or by screws. In addition, a semi-rigid tightening ring with grooves is embedded inside the washer base, and the width of the tightening ring is smaller than the width of the washer base; the ends of the rivets or screws are located in the grooves of the tightening ring, so as not to affect the performance of the torx washer JH is often installed. After the above improvement, Yueluo has improved the one-piece structure of the plum-blossom washer into a split structure and adopted a variety of fixed structure forms, so it has a simple structure, strengthens the impact resistance of the gasket, and can be repeatedly maintained and used. , Extend the maintenance cycle of the equipment and ensure the advantages of the normal production of the enterprise.
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