External hexagonal double threaded step cylindrical bolt, step bolt, non-standard screw

"(1) The surface rust, oil stains, burrs on the bolt hole wall, welding burrs, etc. should be cleaned up.
(2) After treatment of the contact friction surface, it is necessary to meet the specified scratch resistance coefficient requirements. The high-strength bolts used should have matching nuts and washers, which should be used according to the matching requirements and should not be interchanged.
(3) When installing the friction surface of the treated components, it is not allowed to be contaminated with oil, soil, and other debris.
(4) During installation, the friction surface of the component should be kept dry and should not be operated in the rain.
(5) Strictly inspect and correct the deformation of the connected steel plates before installation.
(6) During installation, it is prohibited to hammer into the bolts to prevent damage to the bolt threads.
(7) An electric wrench that is regularly tested during use to ensure torque accuracy and operate in the correct tightening sequence.
Main safety technical measures
(1) The opening size of the Adjustable spanner shall be consistent with the size of the nut, and the small wrench shall not be used to add a sleeve. When working at heights, a dead wrench should be used. If a live wrench is used, a rope should be used to secure it, and people should fasten their safety belts.
(2) When assembling the connecting bolts of steel components, it is strictly prohibited to use hands to insert the connection surface or touch the screw holes. When removing and placing the pad iron plate, fingers should be placed on both sides of the pad iron plate"

"1. The C-grade gasket does not have the requirements for Ra3.2 and deburring. 2. Level C is suitable for medium assembly series, and Level A is suitable for precision assembly series G B848-85 is mainly used for cylindrical head screws, while others are used for standard hexagonal bolts, screws, and nuts.
4. Strength of materials property grade: steel 200HV; Austenitic stainless steel A200. 5. Marking example: Standard series, nominal size d=8mm, performance grade 200HV, plain washer without surface treatment: washer GB97.1-85 8 200HV"

Copper nuts, also known as embedded nuts and inlaid copper nuts or plastic embedded nuts, can be divided into hot-melt copper nuts, hot pressed copper nuts, embedded copper nuts and ultrasonic copper nuts according to the different use methods. This product is widely used in Mobile phone case/pen computer shell/injection molded parts/plastic inserts, and is used as an internal thread. Generally, the external circle is embossed to prevent sliding. Stainless steel hex nut (GB6170/DIN934), thin nut (GB6172/DIN439), heavy nut (metric, American), nylon lock nut (DIN985-DIN982 thick), all metal lock nut (DIN980M), cover nut (DIN1587), flange nut (GB6177/DIN6923), flange nut nylon lock nut (DIN6926), square welded nut (DIN928), hexagonal welded nut (DIN929) Butterfly hats (GB62, DIN315, American), K hats, etc. Specification: M1.6-M64

Washers are divided into: flat washer - C grade, large washer - A and C grade, extra large washer - C grade, small washer - A grade, flat washer - A grade, flat washer - chamfer type - A grade, high-strength washer for steel structure, spherical washer, conical washer, square bevel washer for I-beam, square bevel washer for channel steel, standard spring washer, light spring washer, heavy spring washer, inner tooth lock washer, inner tooth lock washer, outer tooth lock washer, outer tooth lock washer Single ear stop washer, double ear stop washer, outer tongue stop washer, and stop washer for round nuts.