Screw vs Bolt: Unveiling the Key Differences | MachineMFG

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Screw vs Bolt: Unveiling the Key Differences


Generally, the term “screw” does not refer to a fastener but is typically used for transmission.

In rare cases, the term “screw” can specifically refer to the threaded part of a bolt or screw.

Nut: A nut is a component that is screwed together with a bolt or screw to serve a fastening function.

Screws, or fasteners, are general terms, also known as standard parts, which include screws, bolts, and studs.

Stud refers to a type of fastener with no head, only two ends with external threads, such as double-end studs and welding studs. (Sometimes it is called a screw, which I personally think is inappropriate).

The difference between a screw and a bolt is minimal and often confused. There is no particular clear specification boundary, but smaller ones are often called screws. For instance: self-drilling screws, tapping screws, lag screws, etc. Larger screws are known as bolts, such as hex machine bolts, anchors, carriage bolts, etc.

However, generally, a bolt is used to connect two objects, usually through a light hole, and needs to be used in conjunction with a nut to function. Tools typically used are wrenches. The head is often a hex head, and generally larger.

Screws usually do not require nuts and directly match with two objects (the connector usually needs to be drilled and threaded), and the tools typically used are screwdrivers. The head is often a slot, cross slot, internal and external hex, and generally smaller.

 Bolt vs Screw and Screw vs Bolt

Bolt: A type of fastener consisting of a head and a screw (a cylinder with external threads) that must be used in conjunction with a nut to fasten two parts with through holes. This type of connection is known as bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated again, making the bolt connection a detachable connection.

Screw: Another type of fastener also made up of a head and a screw. According to its use, it can be divided into three categories – machine screws, set screws, and special purpose screws.

Machine screws are mainly used for the fastening connection between a part with an internal threaded hole and a part with a through hole, without the need for a nut (this type of connection is known as a screw connection, which is also a detachable connection; it can also be used with a nut for the fastening connection between two parts with through holes. Set screws are mainly used to fix the relative position between two parts. Special purpose screws include lifting eye screws for lifting parts.

The places where bolts and screws are used are different. Bolts do not require high accuracy, unless there are matching requirements.

Generally, bolts are easy to disassemble, have low processing accuracy, are not limited by the connected materials, are widely used, and the required matching bolts can withstand lateral loads. Screws are compact in structure, but they cannot be disassembled frequently and cannot withstand large forces.

In addition, their fastening tools are different. Bolts generally use wrench-type tools, while screws generally use screwdriver-type tools; the fastening methods are different.

Bolts are generally used in conjunction with nuts or screwed into processed bolt holes, and screws in addition to these two methods also have self-tapping screws, which are directly screwed into relatively soft workpieces without processing the bolt hole, such as the wood screw we talk about is this type of screw; the appearance is different.

The head of the bolt is generally adapted to the shape of the tool, such as hexagonal bolts, hex socket bolts, and their heads are exposed outside the workpiece. To make the surface of the workpiece flat, a countersink hole must be made and a hex socket bolt used.

The screw heads are generally flush with the workpiece surface, and those non-self-tapping bolts also need to machine a chamfer on the workpiece surface to make the screw head flush with the workpiece surface.

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