A Brief Description on the Topic SCREWs

1. SCREW
Presentation On A Mechanical Component
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2. Basic Understanding of Screw
A “Nail-shaped” or “Rod Shaped” Piece With A Spiral
Groove And a Slotted or Recessed Head Designed To Be
Inserted Into Material By Rotating And Used For
Fastening Pieces Of Solid Material Together.
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3. Theory of Screw
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When A Screw is turned once, it advances by the
distance between adjacent screw threads. This
Distance is commonly called as “Pitch” of the
Thread. As depicted in the illustration, the handle
also adds a lever. Analyzed from the point of
view of work, the handled is moved one
circumference 2πl to lift the load by the amount
P. So the Ideal Mechanical Advantage is 2πl/P.
The Ideal mechanical advantage is of little
meaning here since there is typically a lot of
friction. But the screw is of enormous usefulness
for the lifting of heavy loads and for use in screw
fasteners which can exert great forces to hold the
object together.
SCREW

4. Types
Head Types,
Thread Types,
Drive Types.
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5. Head Types
The Head of the screw serves to house the drive type of
the screw as well as providing a stopping point once
the screw has been driven into a surface, thus allowing
you to remove the screw if needed.
• Pan: Pan heads are one of the most common head
types; they are slightly rounded and have short
vertical sides to provide a relatively low profile once
driven into surface
• Flat: Flat heads are predominately countersunk and
are designed to sit in the surface that the screw has
been drilled into removing any awkward extent
beyond and above surface that could with further
work on the final product.
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6. Head Types
• Oval: Oval heads provide a combination of pan and
flat head types, with the actual head slightly rounded
while retaining a countersunk underside; they are
primarily used when a decorative finish is needed due
to the aesthetic effects that they provide.
• Truss: Truss heads have a rounded top with a large ,
flat underside that provides an ultra – low profile
while still being above the line of the surface.
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7. Thread Types
Screw threads are the combinations of ridges and
recesses on the body of the screw that allow for
the fixed place via compatible threads inside of a
pre drilled hole or nut, the exterior threads on
screws are thus known as “male” while the
interior threads of their intended are “female”.
 Machine Screw Threads: Machine Threads are the
standard thread type, designed to fit with a pre-
drilled interior thread of a nut or tapped hole,
they have few unique features aside from a high
degree of accuracy when it comes into screwing
into their intended partner thread.
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8. Thread Types
 Wood Screw Threads: Wood Screw Threads
are specifically designed for use in wood ; they
have a sharp, tapered point and wide threads
to allow them to be drilled into a wooden
surface directly rather than requiring a pre
drilled hole to fit into
 Self- Tapping: Self tapping screws are machine
threaded style screws that feature the sharp
tapered pint of screws like the wood and sheet
metal varieties discusses above thus allowing
them to be drilled directly into a surface or to
correct for any inaccuracies in a pre drilled
partner hole.
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9. Drive Types
 Slotted: Slotted drives are a traditional but still popular
style that employs a simple, single slot for a flat-tip
screwdriver. It offers few special properties aside from its
simple design and ease of use.
 Phillips: A Phillips drive has a cruciform shape and is
designed to work with a Phillips screwdriver, the main
advantages of this type of screw are that the extra traction
of multiple edges reduces the amount of force required by
the user, as well as being designed to cause the
screwdriver to pop out of the head recess when subject to
a high degree of force in order to prevent damage to the
screw threads, the downside however is that this often
causes the screwdriver to cause damage to the head
recess itself.
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10. Drive Types
 Pozi: Pozidrive screws are a further development of the
Phillips drive and features two cruciform slots, with the
second being less pronounced than the standard cross
drive. This type of drive offers additional stability and
reduces the built-in slippage of the original Phillips drive.
While still being compatible with the standard Phillips
screwdriver, it is recommended to use a specific Pozidrive
screwdriver to avoid damage to the head.
 Square: While not as common as the standard slot and
Phillips drives, square screw drives enjoy popularity in
Canada and a number of other countries. The simple
shape of the square drive allows a square screwdriver to
be inserted and twisted easily without having to worry
about positioning to ensure precision threading. The
spread out contact area however is not useful for
transferring a high degree of force if needed
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11. Drive Types
 Hex Socket: Hex socket drives feature a hexagonal recess and
are driven with the use of a hex key or hex screwdriver, the
main benefit of this type of drive is the high number of
contact surfaces reduce the amount of force required to turn
the screw while also helping to reduce slippage and thus
damage to the screw, the downside being that the amount of
force that can be used with this drive type is limited much
like the square drive socket.
 Star: Star drives or “Torx” drives have a star shaped recess
with six rounded points. It’s primary benefits are a reduction
in the amount of force required to turn the screw as well as
effectively eliminating slippage while maintaining the
longevity of the screw and the driver used, which is a
specialist Torx screwdriver. There are also a variety of
tamper-resistant star drive types that include pins in the
centre of the main recess that require a highly specialized
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12. Design And Consideration
On A Single thread screw , the lead and the pitch are identical, lead
is twice the pitch on a double thread model, and three times as
much on a triple thread. The pitch of a screw is a the distance
between two threads from the same point on each thread. It is
also more commonly known as the number of threads per inch
or centimeter. The lead of the screw measures how far it is
driven in for each revolution.
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13. Material Used In Construction
Screws are generally made from low to medium carbon steel
wire, but other tough and inexpensive metals may be
substituted, such as stainless steel, brass, nickel alloys, or
aluminum alloy. Quality of the metal used is of utmost
importance in order to avoid cracking. If a finish is applied to
the screw, it must be of a compatible make up. Steel may be
coated or plated with zinc ,cadmium, nickel, or chromium for
extra protection.
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14. Manufacturing Process
Machining is only used on unique designs or with screws too small to be
made any other way. The Machining process is exact but too time
consuming, wasteful, and expensive. The bulk of all screws are mass
manufactured using the thread rolling method, and that is the
procedure described in further detail.
Cold Heading, Wire id fed from a mechanical coil through a
prestraightening machine. The straightened wire flows directly into a
machine that automatically cuts the wire at a designated length and
die cuts the head of the screw blank . On average, the cold heading
machine produces 100 to 550 screw blanks per minute.
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15. • Thread Rolling, Once cold headed, the screw blanks are automatically
fed to the thread-cutting dies from a vibrating hopper. The Hooper
guides the screw blanks down a chute to the dies, while making sure
they are in the correct feed position.
• The Blank is then cut using one of the three techniques. In the
reciprocating die, two flat dies are used to cut the screw tread. One
die is stationary, while the other moves in a reciprocating manner, and
the screw blank is rolled between the two. When a centre less
cylindrical die is used , the screw blank is rolled between two to three
round dies in order to create the finished thread. The final method of
thread rolling is the planetary rotary die process. It holds the screw
blank stationary, while several die-cutting machines roll around the
blank
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16. Quality Controls & Testing
The National Screw Thread Commission established a standard
for screw threads in 1928 for interchangeability. This was
followed by an international Declaration of Accord in 1948,
adopting a Unified Screw Thread system. The standards focus
on three main elements: the number of threads per inch, the
designated pitch and shape of the thread, and designated
diameter sizes. In 1966, the International Standards
Organization (ISO) suggested a universal restriction on threads
to ISO metric and inch size ranges with coarse and fine
pitches. Compliance with the ISO suggested standards has
been global.
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17. Manufacturing Organizations
India Based Companies:
 Mascot Enterprises
 Kirit Industries
 Kaarthic Worms
 Sterling Industries
 Kiran Industries
 Arya Technoseals Pvt Ltd
 Malkar Industries
 Saroj Enterprises
 R.P Engineering Works (Indore)
China Based Companies:
 Shenzhen ENNER Electronics
Technology Ltd.
 Yugao Fastener Factory Ltd.
 Dongguan City Aoyi Hardware
Ltd.
 Shanghai Everise Tool Industrial
Ltd.
 Shenzhen Wandaan Precision
Technology Ltd.
 Kang Yang Hardware Enterprises
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18. Reference Sources
 www.hyperphysics.org
 www.indiamart.com
 www.eurofitdirect.co.uk
 www.madehow.com
 www.globalsources.com
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19. A P r e s e n t a t i o n B y
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Thank You