Screw knowledge

Learn more about SCREWS

What is the difference between bolt and screw?

Bolt: Generally used with a nut.
Screw: Screw requires at least on component with a thread or called “Male thread” .”female thread” means “internal thread”. But even now, there is confusion in distinguishing between “screw” and “bolt”.

Origin of screw

The origin of screws is not clear.
According to contemporary history, the first screw was made for a machine . Some say that the thread structure could only be imagined by a genius mechanicist like Archimedes.

Production method and development of standardization

1850s In Europe, the cold forging method Began to develop, a large number of interchangeable screws were made.

After the interruption of the World War II period, the International Organization Standardization (ISO) was established in 1947. and the international standardization was promoted even with screw standards. The “ISO metric thread” standard was enacted.

What is Washer?

A washer is use to be placed under the nut when tightening the bolt and nut, to provide protection between fasteners and target.. It is standardized corresponding to the screw diameter.

What is the function of washer?

.Surface protection

It is used to prevent sinking of the nut or bolt head into the target (bearing surface collapse), or when the hole diameter is larger than the bolt diameter, to stabilize the target surface.

.Anit loose

Washer can prevent the bolt / nut from loosening due to vibration.


Soft materials such as copper and aluminum, rubber, polycarbonate, PTFE and other materials are also used to keep airtightness.

.Insulation / Conduction

Washer can also provide Insulation or Conduction function.

.Flat washer

Flat Washer(Plain washer) when the through hole is large that screw or when a surface against the axial force can not be obtained, it is necessary to use washer to considering the bearing surface strength and the axial force.