screw

A screw (colloquially a screw or a screw, unwritten a screw or a screw) is a machine part that is part of dismountable joints, based on the principle of interlocking external (bolt) and internal thread (nut). By turning the thread, the screw moves, or to move the body in the thread.

History

 The screw was invented more than 2,000 years ago, but it has only been used for fastening for less than 500 years.

The screw was first described by the Greek scholar Archimedes of Syracuse (approx. 287-212 BC). Archimedes' screw was a huge spiral enclosed in a wooden cylinder. They used it to irrigate fields and to move water from a lower level to a higher one.

Archimedes probably did not invent the screw, but merely described an object that already existed. Perhaps it was invented by ancient Egyptian technicians to irrigate fields near the banks of the Nile. Archimedes' screw was used in ancient times to pump water to a greater height. However, no one thought of using a screw for fastening. Medieval carpenters and carpenters used wooden pegs or metal wedges to assemble furniture and wooden building structures.

In the 16th century, nails with a thread began to be produced, which held better. That was only a step towards the creation of the screw. Screws did not become widely used for fastening until the late 18th century, when they figured out a method to make them cheaply.

The principle

 

Screw joint - nut + screw
The force turning the screw is less than the force moving the screw. The thread is actually a twisted inclined plane, the force of movement along the inclined plane (for screws, the movement along the thread during rotation) is less than the force required to lift the body without the inclined plane (for screws, the movement of the entire screw). The force F1 required to turn the screw:{\displaystyle F_{1}={\frac {F_{2}.d}{2\pi r}}}

where F2 is the force that moves the screw, d is the height of 1 thread, r is the radius of the screw.

In technical practice, a screw is one of the basic fasteners, either alone, together with a nut, or as a set screw.

Splitting screws
metric (60° apex angle) designation M
metric fine
Whitworth (apex angle 55°) W
tubular G
round thread Rd
Edison screw E
trapezoidal isosceles Tr
trapezoidal unequal S*tubular
According to the thread direction
clockwise
left-handed (indicated by notches on the head)

 

a) clockwise (most often used)
b) multiple (e.g. M16x3/2)
c) left-handed (e.g. M16 LH)

 

According to the screw head
without head - adjusting screw, so-called "worm"
with the head

 

Screw connection without a head - adjusting screw, so-called worm

According to the type of screw head

not embedded
with a hexagonal head
with square head
with a cylindrical head
with a lenticular head
with a half-round head
embedded
with a flat head
with a lenticular head
with a half-round head

 

According to the type of drive (grooves)

The shape of the slot for the screwdriver
with a flat groove
with an internal hexagon - the so-called allen
Pozidriv
Phillips - the so-called cross
Torx (internal hexalobular groove) and Torx Plus