What is the tolerance range of precision screws?
What is the tolerance range of precision screws?
The marking format of the thread mark is: Thread code - thread tolerance zone code (pitch diameter, top diameter) - screw length l) Tolerance zone code is represented by numbers plus letters (inner thread with uppercase letters, external thread with lowercase letters) , such as 7H, 6g, etc., it should be specially pointed out that 7H, 6g, etc. represent thread tolerance, while H7, g6 represent cylinder tolerance code. 2) The length of rotation is specified as short (represented by S), medium (represented by N), and long (represented by L). In general, the thread engagement length is not marked, and the thread tolerance zone is determined by the medium engagement length (N). If necessary, add the screw length code S or L, such as M20-5g6g-L. When special needs are required, the value of the screwing length can be indicated, such as M20-5g6g-30.
Moisture-proof measures Iron screws are easy to rust in a humid environment. In order to prevent the screws from rusting, the screws need to be moisture-proof and moisture-proof. The moisture-proof and moisture-proof methods of screws are as follows: (1) Vibration machinery, try to use solvent-free paint. (2) It is best to use impregnating paints that do not contain oxidative components, such as epoxy-urethane (Epoxy-urethane)-based or unmodified epoxy-based (Epoxy-)-based impregnating paints. (3) When using melamine alkyd impregnating paint, the curing temperature and curing time should be adjusted. The curing temperature should be slightly higher than 130 °C (such as 135 °C) and the curing time should be longer than 180min, and the process must be strictly implemented, especially In the hot and humid season, the drying (curing) time of the paint specified in the paint factory's samples is not necessarily sufficient from the perspective of rust prevention, and the motor has a specific inner shape. (4), use paint without volatile acid. (5) Choose paint with good hydrolysis resistance.
The main purpose of the embedded nut is to replace the direct opening of screw holes on the injection molded parts, so as to improve the strength of the screw holes of the injection molded parts. Referring to FIG. 1 , in order to lock the workpiece 3 ′ on the injection molded part 2 ′, the screw 5 ′ passes through the through hole on the workpiece 3 ′ and is screwed into the screw hole of the embedded nut 1 ′ to fix the workpiece 3 ′. The embedding between the embedded nut 1' and the injection-molded part 2' generally includes two ways. One is to heat the embedded nut 1' and then insert it into the injection-molded part 2' by hot pressing; the other is to insert the embedded nut into the injection-molded part 2'. 1' and the injection part 2' are integrally injection-molded. In order to ensure the bonding strength between the inner nut 1' and the injection molded part 2', knurling is provided on the outer peripheral surface of the inner nut 1'.
through-hole mounting nut, comprising a hexagonal portion 1 and a cylindrical portion 2, a threaded hole 3 is provided between the hexagonal portion 1 and the cylindrical portion 2, and two grooves 4 are opened on the cylindrical portion 2, and each of the two sides of the groove 4 has a The raised side 5, the two sides protruding from the sheet metal part 7, if squeezed or hit by the bolt 8, it will bend to both sides and buckle on the sheet metal part, so that it is not welded directly. Rubber can also be used. Each of the upper surfaces of the side edges 5 is provided with a convex point 6 so that the hammer will not slip when hitting.
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