Screws are the most common form of joining technology. There are literally hundreds of
screws. Every screw needs to be turned in order to fit tightly with the object joined.
This turning is done with the help of a tool called screw driver. The screw driver fits
into the head of the screw and turns it. Every screw has a different tool to be driven or
turned. In this video , we will take a look at a few
of the most popular kinds of screw heads. Most screw head such as Slotted, Phillips,
Pozidriv, hexagonal and square head screw profiles are common.
Slotted screw. The slotted screw has been around the longest.
This is the traditional screw head in which used to be the only head type available. The
slotted head is basically one line through the middle of the head in which the screwdriver
would fit. Once the edges of the slot is burred, the screw then becomes unusable.
Phillips screw. The screw head, Phillips has been named after
its creator, Henry F. Phillips. It has a cross-shaped recess on the head, i.e. two slots at 90 degrees
to each other. The force that is required to turn the screw is less which is why it
better than the slotted screw drive. Like the slotted drive, this screw head too causes
the screw driver to cam out when high torque is applied to tool. However, the intensity
is lesser compared to that of the slotted drive. Hence, the damage is limited to the
screwdriver instead of the work or the screw head. The purpose of its design was to make
the driver came out so that it did not result in over-tightening. It has applications in
home and workshops.
Pozidrive screw. The Pozidrive screw has a total of eight points
of contact, this is done by adding a second cross to the first cross and it improves the
contact of the driver to the screw. This is more versatile than a Phillips head and also
has a superior grip. This head may be used with a slotted screw driver or a Pozidriver.
Square or Robertson screw. This square screw driver has been named after
the Canadian inventor, P. L. Robertson. It a square-shaped recess in the screw head,
which holds the tool firmly. It is also called a Robertson drive. They are highly resistant
to coming out which is why they are being used more. The driver does not slip off the
head easily even when high force is applied to it. They are used by woodworkers, electricians
and motor mechanics. Hexagonal screw.
These head types are made to extend above the surface and is driven by using either
a hexagonal driver or a spanner. These fasteners are very similar to hex bolts. They differ
mostly in that they are used to tighter tolerances than the corresponding bolts.
One-way screw. These screws have slots which are narrow at
the center and gets wider as they proceed towards the edges. They can be turned only
in one direction. The shape of the slot allows a flat-bladed screw driver to rotate the head
in the driving direction, but not in the removing direction. They can have either a flat head
or a round head. They are used in restroom fixtures and on vehicle registration plates.
They are mostly used in thin metal or wood. Torx Head screw.
These head types have a six pointed recess which makes the drive easier in that there
is a larger surface area. They require a less common driver to suit them called a Torx driver.
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