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The difference between bolts and screws
Date：May 3rd,2023
From the bolts and screws listed in the national standard, the characteristics of bolts is that its head has three forms (except anchor bolts, live bolts and other special bolts), hexagon head, square head (including T bolts) and round head, round head bolts are generally countersunk bolts with tenon or neck. The head feature of the screw is basically round, with a word slot, a cross slot and an inner hexagonal hole (including the inner hexagonal flower hole in the circle). In one sentence to judge whether it is a bolt or a screw, the head is round without tenon and neck, the rest is a bolt, this is the most intuitive way for us to judge whether it is a bolt or a screw.
Bolts and screws (excluding self-tapping screws and wood screws, unlike the type of machine screws, and the same type of machine screws) are threaded fasteners including bolt connection, double stud connection and screw coupling (including tightening screw connection).
The characteristic of bolt connection is that the connecting part of the connection part is through the hole, and the bolt connection pair is generally composed of bolts, nuts and washers.
The characteristic of double-head stud connection is that one of the joints needs to be processed into threaded holes, and the rest of the joints are processed into through holes. The double-head stud coupling pair generally includes double-head stud, nut and gasket. This kind of connection is suitable for the structure cannot be bolted, such as one of the connections is too thick to make through holes.
Screw connection (without tightening screw) is characterized by one of the connected parts also needs to process the threaded hole, the rest of the connecting parts are processed into the hole, the screw directly into the threaded hole of the coupling, but the screw connection does not need a nut, only screws and washers. This coupling is simpler and more compact in structure than the double-headed stud. Its use is similar to that of the double-head bolt connection.
Tightening screw connection is to use the end of the screw screwed into the thread hole of the part to resist the surface of another part or into the corresponding pit, to fix the relative position of the two parts, and can transfer little force or torque.
From the concept of fastener connection, the significant difference between screw and bolt is whether the connection is nut.
Currently in national standard bolt type has 57 (including 15 combinations and bolt connection auxiliary bolts, and 2 bolt standard in the 5th edition of the mechanical design manual, but has been abolished), national standard screw type 68 (including 10 combinations used screws, two standard with bolts).
In general, 57 national standard bolts are used in bolt connection occasions, and 68 national standard screws are used in screw connection occasions. However, in some cases, bolts are used for screw connection (usually hexagon head bolts) and bolts are used (rarely used).
Bolts and screws (excluding self-tapping screws and wood screws, unlike the type of machine screws, and the same type of machine screws) are threaded fasteners including bolt connection, double stud connection and screw coupling (including tightening screw connection).
The characteristic of bolt connection is that the connecting part of the connection part is through the hole, and the bolt connection pair is generally composed of bolts, nuts and washers.
The characteristic of double-head stud connection is that one of the joints needs to be processed into threaded holes, and the rest of the joints are processed into through holes. The double-head stud coupling pair generally includes double-head stud, nut and gasket. This kind of connection is suitable for the structure cannot be bolted, such as one of the connections is too thick to make through holes.
Screw connection (without tightening screw) is characterized by one of the connected parts also needs to process the threaded hole, the rest of the connecting parts are processed into the hole, the screw directly into the threaded hole of the coupling, but the screw connection does not need a nut, only screws and washers. This coupling is simpler and more compact in structure than the double-headed stud. Its use is similar to that of the double-head bolt connection.
Tightening screw connection is to use the end of the screw screwed into the thread hole of the part to resist the surface of another part or into the corresponding pit, to fix the relative position of the two parts, and can transfer little force or torque.
From the concept of fastener connection, the significant difference between screw and bolt is whether the connection is nut.
Currently in national standard bolt type has 57 (including 15 combinations and bolt connection auxiliary bolts, and 2 bolt standard in the 5th edition of the mechanical design manual, but has been abolished), national standard screw type 68 (including 10 combinations used screws, two standard with bolts).
In general, 57 national standard bolts are used in bolt connection occasions, and 68 national standard screws are used in screw connection occasions. However, in some cases, bolts are used for screw connection (usually hexagon head bolts) and bolts are used (rarely used).