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Basic Knowledge of Fasteners

What are fasteners?

Fasteners are the general terms for similar mechanical parts, which integrate two or more parts and members into one entity. They are also called standardized parts on market.

Types of fasteners usually include the parts as follows:

Bolts, double-screw-bolt, screw, nut, self-tapping screw, wood screw, joint ring, retainer ring, pin, rivet, assembling unit, connection pair, welding stud.

1. Bolt: it is a kind of fasteners consisting of the head parts and screw which is s cylinder with external thread. It is used to combine tightly two parts with through-holes together and tie in with the nut. This connection is called bolt connection. If you take the nut off from the bolt with rotation, you can separate these two pats. Therefore the bolt connection is removable in the connection of fasteners.

2. Double-screw-bolt: the two terminals have external thread and it has no head part. When connecting, you should rotate it into a part with internal thread hole at one end, and put the through-hole part into it, rotate the nut upon it, thus these two parts are connected together tightly. This connection is called double-screw-bolt connection and it is also removable connection. This connection is mainly used when the parts are too thick to connect and the structure is compact, or the situation of frequent dismantling.

3. Screw: it comprises of head part and screw. It includes steel screw, set screw and screw for special purpose according to its applications. Machine screw is mainly used to connect the part who has set threaded holes with a part who has through holes. It is not in tie with nut. This connection is called screw connection which is also removable. It can be in tie with nut to fasten two parts with through-hole together. Set screw is mainly used to fasten two parts in a relative locations. Screw for special purpose is used to hoist parts like lifting eye bolt and many more.

4. Nut: it has internal thread hole, and it has types of shapes like flat hexagonal column, flat square column and flat cylindrical. It often works with bolt, double-screw-bolt and steel screw to fasten two parts and integrate them into one entity.

5. Self-tapping screw5. self-tapping screw: it is a fastener similar to screw but its thread is exclusive as the self-tapping screw. It is used to fasten two thin metal constructions and integrate them into one entity. It is necessary to make out small holes upon the constructions first. For it has high hardness, it could form out the correspondent thread on the constructions when rotating it into the constructions. This connection is also removable.

6. Wood screw: it is a kind of fasteners smiliar to screw but its thread is exclusive as the wood screw. You can fasten a metal or non metal part with through-hole and wooden part together. This connection is also removable.

7. Joint ring: its shape is oval ring. It locates between the bearing surface of bolt, screw and nut and the surface of other parts. It can broaden the superficial area of connecting parts, decrease the unit area pressure and prevent the contact area to be destroyed. And the elastic ring can prevent the nut to be loose.

8. Retainer ring: it is used in the steel construction, or axial trough and hole groove in the equipment so that the parts on the axis or in the hole cannot move around.

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