Page 79 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

1
64 Automobile mechanical and electrical systems

Figure 1.90 Nuts and bolts

P/8
INTERNAL THREAD
H/8

60° 3H/8
P/4
H
30° 5H/8
P/2
D maj
H/4
D
p
EXTERNAL THREAD
D min P

90°
AXIS OF SCREW THREAD

Figure 1.91 ISO metric thread profi le

some engines are made from sophisticated high tensile steel so that they will
stretch. The size of the nut and bolt will depend on the size of components to be
secured. Thread sizes used to be a problem, but fortunately now most nuts and
bolts are metric. Figure 1.91 shows a metric thread profi le.
Metric nuts and bolts are described as in the following example:

M10 1 5.
The M is metric, the 10 is the bolt diameter and the 1.5 is the pitch of the thread.
When joining with nuts and bolts it is common to fi nd fl at washers and in many
Key fact
cases some type of locking device. Metric threads are quite good at locking in
Vibration is the main cause of bolts position as they are, but for safety, extra devices are often used. Vibration is the
coming loose. main cause of bolts coming loose, as well as their not being tightened to the
correct torque in the fi rst place. Figure 1.88 shows a selection of locking devices,
including a Nyloc (nylon lock) nut at the top right.