2. Selected Types of Bolts and Screws
Bolts and screws made of steel are used in machines, steel
structures, vehicles and ships because of their strength and toughness. They may
be electrically plated with cadmium, zinc, copper or brass.
Bolts and screws made of copper, brass or light metal are used
in electrical equipment because they conduct electricity and do not corrode
easily.
Hexagon head screws
Used mainly for iron and steel work and in machines generally.
There are hexagon head screws of different sizes and lengths of thread in
accordance with ISO metric coarse and fine threads.
Typical designation:
Hexagon Head Screw M6 x 20
- Nominal diameter of the ISO metric thread
(coarse): 6 mm
- Length of engagement (without the head): 20 mm
Figure 2. Hexagon head screw
1 nominal diameter, 2 length of
engagement
Countersunk head screws
Used in industrial plant and equipment, where safety requires
that no head projects the surface of any component. There are countersunk head
screws of different sizes and lengths of thread according to ISO metric coarse
thread, with different shapes of slots and tops of heads.
Typical designation:
Countersunk bolt with cross slot M6 x 20
- Nominal diameter of the ISO metric coarse thread:
6 mm
- Length of engagement (with the head): 20 mm
Figure 3. Countersunk-head
screw
1 nominal diameter, 2 length of
engagement
Cheese head screws
Used for light-weight structured and in general engineering.
There are cheese head screws of different sizes and lengths of thread according
to ISO metric coarse thread, with different shapes of head. Fillister
socket-head screws can accept draw-in forces.
Typical designation:
Cheese head screw with cross slot M6 x 20
- Nominal diameter of the ISO metric coarse thread 6
mm
- Length of engagement (without the head) 20 mm
Figure 4. Cheese head screw
1 with cross slot, 2 with hexagonal socket
head
Other ISO metric thread bolts and screws
Generally used in the field of engineering, restricted use in
machines. There are different sizes and shapes of the head as well as various
designs in bolts.
Figure 5. Other bolts and
screws
1 threaded pin, 2 stud bolt, 3 knurled head
screw, 4 eye-bolt, 5 thumb screw, 6 square bolt
Sheet metal screws
Generally used for car bodies, vessels and light-weight
structures. The thread on the cylindrical portion of the screw (with the tip)
cuts itself the thread in soft sheets. There are sheet metal screws of different
sizes, lengths and shapes of the head. The threaded portion always extends over
the entire length of the shank (with the tip), just up to the head.
Figure 6. Sheet metal screws
1 button-head sheet metal screw with cross slot,
2 oval head sheet metal screw with intersecting slots, 3 countersunk-head sheet
metal screw with cross slot, 4 metric self-tapping screw
Wood screws
Wood screws are used in wood structures. The thread on the
tapered portion of the shank (with the tip) cuts itself the thread in the wood.
There are wood screws of different sizes, lengths and shapes of the head. Only
the tapered portion of the shank is threaded, followed by a cylindrical neck.
Figure 7. Wood screws
1 hexagon head wood screw, 2 button-head wood
screw, 3 countersunk wood screw
Where are countersunk head screws
used?
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What is the difference in the lengths of engagement of a cheese
head screw and a countersunk head
screw?
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Where does the shape of a sheet metal screw differ from that of
a wood
screw?
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