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What is the difference between the three concepts of bolt, screw and screw?

What is the difference between the three concepts of bolt, screw and screw?

An indispensable part of industrial castor installation is bolt. In life, bolts, screws, screws, etc., are often mentioned. What is the difference between them?

The head of the bolt is generally hexagonal and the rod part has an external thread.

The screw is small, the head has flat head, cross head, rod part with external thread.

Screw is commonly known, the standard is that there is no screw, with external threads can be called “screw”.


Other related accessories are:

Nut is commonly known, the standard is no nut, the standard should be called “nut”. The shape of the nut is usually hexagonal, the inner hole is internal thread, used to match with the bolt, tighten the relevant parts.

Stud should call actually “double stud”, both ends all have external thread, the middle is generally smooth rod. The long end of the thread is used to connect with the deep hole, and the short part is used to connect with the nut.

Standard fasteners are divided into twelve categories, which are determined according to the use occasions and functions of fasteners.

1, the bolt

Bolts are widely used in mechanical manufacturing for detachable connections and are generally used with nuts (usually with one or two washers).

a) General purpose bolts: there are many varieties, including hexagon head and square head. Hexagonal head bolt application is the most common, according to the manufacturing accuracy and product quality is divided into A, B, C and other product grades, to A and B grade applications, and is mainly used for important, high assembly accuracy and by large impact, vibration or variable load place. Hexagon head bolt according to its head supporting area size and installation position size, can be divided into hexagon head and large hexagon head two; The head or screw has holes for use when the need for locking. The square head of the square bolt has a larger size and force surface, which is convenient for the wrench mouth to get stuck or other parts to start and stop. It is commonly used in the rough structure, sometimes also used in the T-groove, which is convenient for the bolt to loosen and adjust the position in the groove;

b) Bolt for hinged hole: when used, the bolt is tightly inserted into the hinged hole to prevent workpiece dislocation;

c) Stop bolt: square neck, with tenon;

d) Special purpose bolts: including T-groove bolts, knuckle bolts and anchor bolts. T-groove bolts are often used to open the connection; Anchor bolts are used to fix the frame or motor base in the cement foundation;

e) Steel structure with high strength bolt connection pair: generally used for building, bridge, tower, pipe support and lifting machinery and other steel structure friction connection occasions.



2, screw

Screws are usually used alone (sometimes with a washer), generally to tighten or tighten the role, should be screwed into the body of the internal thread.

a) Machine screw: it is divided into many varieties because of the different head type and groove shape. The head type has cylindrical head, pan head, countersunk head and half countersunk head, the head groove shape is generally slotted (a word groove), cross groove and hex socket three kinds. Cross groove screw is good to neutral, head strength than a word groove, not easy to screw bald, generally used in mass production. Hexagon socket screw, hexagon socket screw can apply a larger tightening torque, high connection strength, the head can be buried in the body, for the requirements of compact structure, smooth shape of the connection;

b) Setting screw: The setting screw is used to fix the relative position of the parts, and the head is of type of slotted, hexagon socket and square head. The square head can apply a large tightening torque, the jacking force is large, not easy to screw bald, but the size of the head is large, it is inconvenient to bury in the parts, is not safe, especially the moving parts should not be used. With a slotted, hexagon socket is easy to sink parts. Set screw end according to the use of different requirements, generally the most commonly used cone end, flat end, cylindrical end three. Taper end is suitable for small hardness parts; When using non-pointed cone end screws, holes should be made on the top tightening surface of the parts, and the cone surface should be pressed on the edge of the hole. The SCREW WITH flat end has large contact area and does not damage the surface of the parts after jacking. It is used for jacking the plane with large hardness or the occasions where the position is often adjusted. The screw at the end of the cylindrical end does not damage the surface of the parts. It is mostly used to fix the parts mounted on the tube shaft (thin-walled parts). The hole of the cylindrical end into the shaft is kind, and the shear resistance of the circular end can transfer a large load.

c) Hex socket screw: Hex socket screw is suitable for small installation space or the screw head needs to be buried;

d) Special purpose screws: such as positioning screws, non-popping screws and lifting ring screws.

3. Wood screws

Wood screws are used to screw into wood for joining or fastening.

Divided into many varieties by head type and groove type. The head type has a round head, countersunk head, half countersunk head several kinds, the head groove shape is slotted (a word groove) and cross groove two kinds.

4. Self-tapping screws

The working screw hole matched with the tapping screw does not need to be tapped in advance, and the internal thread is formed when the tapping screw is screwed into the screw.

a) Common tapping screw: thread conforms to GB5280, large pitch, suitable for use on thin steel plate or copper, aluminum, plastic;

b) Self-tapping locking screw: thread conforms to ordinary metric coarse tooth thread, suitable for use in situations requiring vibration resistance.

5, nut

a) General purpose nuts: hexagon nuts, square nuts, etc. Hexagon nut with hexagon bolt is the most common application, according to the manufacturing accuracy and product quality is divided into A, B, C and other product levels. Thin hexagonal nuts are used as sub-nuts in anti-release devices for locking purposes or where threaded connection pairs mainly bear shear forces. Hexagon thick nuts are used for frequent disassembly connections. Square nut with square bolt, wrench stuck not easy to slip, mostly used in rough, simple structure;

b) slotted nuts: mainly refers to hexagonal slotted nuts, that is, the grooves are processed above the hexagonal nuts. It is used with screw bolts with holes and cotter pins to prevent the relative rotation of bolts and nuts;

c) Lock nuts: refers to the nuts with locking function, including hexagonal lock nuts with nylon inserts and full-metal hexagonal lock nuts, etc. Hexagonal nylon ring lock nut has very reliable anti-loose ability, in the use of temperature -60 ~ +100℃ and certain medium conditions, with no damage to the bolt and the connecting piece and can be frequently loaded and unloaded.

d) Special purpose nuts: such as butterfly nuts, cover nuts, knurled nuts and insert nuts, etc. Butterfly nut generally can be disassembled without tools, usually used for frequent disassembly and force is not large places; Cover nuts are used where end studs require a cover.

6, stud

Stud is used to connect one of the connected parts thickness, need to use a compact structure or due to frequent disassembly and should not be bolted connection. The stud is generally threaded at both ends (single stud is a single end with thread), usually a head of thread firmly screwed into the body of the component, the other end and nut match, a connection and fastening role, but to a large extent also has the role of distance.

a) Unequal length double-headed stud: applicable to the occasions where one end is screwed into the body of the part to connect or fasten;

b) Double stud of equal length: suitable for connecting or setting distance between the two ends and the nut.

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