We are used to calling small bolts bolts and big bolts bolts.

The differences between screws and bolts in the “Manual of Mechanical Design” published in the United States are as follows:

Bolts are screw fasteners with threaded outer rings.

The purpose is to insert the bolt into the hole and secure the assembly. Usually tightened or loosened with nuts and swivel nuts.

A screw is also a screw fastener with an outer ring thread for the purpose of inserting the bolt into the hole and securing the component.

And usually the existing internal thread is mounted on the hole, or the cap of the internal thread produced by the screw in the hole. The screw head is usually rotated to tighten or loosen the screw.

If the fastener has external threads, it can only be tightened or loosened after assembly by a swivel nut, i.e. bolts (e.g. flat round head bolts, track bolts, anti-loose bolts).

If the fastener has an external thread and is not used with the nut, it is a screw (e.g. wood screw, tapping screw, mechanical screw).

These differences are consistent with definitions of bolts and bolts in ASME B18.2.1 and in some dictionaries. However, there are other ways to define it.

A screw, or fastener, is a general term, also known as a fastener or standard part. Screws include screws, bolts and studs.

Stud, a type of fastener without a head but with external threads at both ends.

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For example: double end stud, welding stud, etc. (sometimes called screw, personal do not think appropriate).

The difference between a screw and a bolt is minimal and is often confused. There is no definite size line, but the smaller one is usually called a bolt.

Such as self-drilling screw, tapping screw, lag screw, etc. Larger screws are called bolts, such as hex machine bolt, anchors, carriage bolt, etc.

But in general, a bolt is used to connect two objects, usually through a light hole. It needs to be used with a nut.

Tools usually use a wrench. The head is mostly hexagonal, generally larger.

The screw usually does not need the nut, directly with the two objects (general connector first to drill, tapping), the tool generally with a screwdriver (screwdriver).

The head is a word slot, cross slot, hexagonal inside and outside is also a lot of, generally smaller.

Bolt: A type of fastener consisting of a head and a screw (the screw refers only to the threaded part.

Not the same concept as the drive screw) that is fitted with a nut for fastening two parts with through holes.

Screw: A type of fastener consisting of a head and a screw, which can be classified into three categories according to their use — machine screws, setting screws, and screws for special purposes.