chap09 pps Automotive technology at University of Cambridge

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Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
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OBJECTIVES:
After studying Chapter 9, the reader should
be able to:

•
•
•
•

Describe what tool is best to use for each job.
Discuss how to safely use hand tools.
Explain the difference between the brand name
(trade name) and the proper name for tools.
Explain how to maintain hand tools.

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KEY TERMS:
adjustable wrench • aviation tin snips • beam-type
torque wrench • box-end wrench • breaker bar (flex

handle)
cheater bar • chisel • clicker-type torque wrench • cold
chisel • close end • combination wrench • crowfoot
socket
dead-blow hammer • diagonal (side-cut or dike) pliers •
double-cut file • drive size • easy out • extension
files • fitting wrench • flare-nut wrench • flat-tip (straight
blade) screwdriver • hacksaw • locking pliers
Continued
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KEY TERMS:

(cont.)

multi-groove adjustable pliers • needle-nose pliers • nut
splitter
offset left aviation snip • offset right aviation snip • openend wrench • punch • ratchet • removers
screwdriver • seal driver • seal puller • single-cut file •
slip-joint pliers • snap-ring pliers • socket • socket
adapter • straight cut aviation snip • stud removal tool •
stud remover
tin snips • torque wrench • tube-nut wrench • universal
joint • utility knife • VISE GRIPS ®• water pump pliers •
wrench
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WRENCHES
Wrenches are the most used hand tool by service techs. Most are
constructed of forged alloy, usually chrome-vanadium steel.
The wrench is formed, hardened, tempered to reduce brittleness,
and then chrome plated. There are several types of wrenches.

Figure 9–1 A forged wrench after it has been forged but before the flashing, extra material
around the wrench has been removed.
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Open-End Wrench An open-end wrench is used for bolts or
nuts that do not require a lot of torque. It can be easily placed on
a bolt or nut with an angle of 15 degrees.
The disadvantage of an open-end wrench is lack of torque that
can be applied, as the open jaws of the wrench only contact two
flat surfaces of the fastener.
An open-end wrench has two different sizes; one at each end.

Figure 9–2 A typical open-end wrench. The size is different on each end and notice that the
head is angled 15 degrees at each end.
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Box-End Wrench A box-end wrench, is also called a close-end
wrench, has two different sizes; one at each end. It is placed over
the top of, and grips the points of the fastener.
Figure 9–3 A typical box-end wrench is able
to grip the bolt or nut at points completely
around the fastener. Each end is a different
size.

Figure 9–4 The end of a box-end
wrench is angled 15 degrees to allow
clearance for nearby objects or other
fasteners.

A box-end wrench should be used to loosen or to tighten fasteners.
Continued
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Most service technicians purchase combination wrenches, which
are open at one end and have the same size box on the other end.

Figure 9–5 A combination
wrench has an open end at one
end and a box end at the other.

A combination wrench allows the tech to loosen or tighten a
fastener using the box end of the wrench, and turn it around to
use the open end to increase the speed of rotating the fastener.

Continued
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Adjustable Wrench An adjustable wrench is often used where the exact
size wrench is not available or when a large nut, such as a wheel spindle nut,
needs to be rotated but not tightened.

Figure 9–6 An adjustable wrench. Adjustable wrenches
are sized by the overall length of the wrench and not how
far the jaws open. Common sizes include 8, 10, and 12 inch.

An adjustable wrench should not be used to loosen or tighten
fasteners because the moveable jaws can loosen their grip on the
fastener, causing it to become rounded.
Continued
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Line Wrenches Called flare-nut wrenches, fitting wrenches, or
tube-nut wrenches. Designed to grip almost all the way around a nut
used to retain a fuel or refrigerant line, and yet able to be installed
over the line.

Figure 9–7 The end of a typical line wrench, which shows that it is capable of grasping most
of the head of the fitting.
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Safe Use of Wrenches Wrenches should be inspected before use
to be sure they are not cracked, bent, or damaged. They should be
cleaned after use.
Always use the correct size of wrench for the fastener being
loosened or tightened to prevent the rounding of the fastener.
When attempting to loosen a fastener, pull—do not push— a
wrench. If a wrench is pushed, your knuckles can be hurt when
forced into another object if the fastener breaks loose.

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RATCHETS, SOCKETS AND EXTENSIONS
A socket fits over the fastener and grips the points and/or flats. It
is rotated (driven) using either a long bar called a breaker bar
(flex handle) or a ratchet.

Figure 9–8 A typical ratchet used to rotate a socket. A ratchet makes a ratcheting noise when
it is being rotated in the opposite direction from loosening or tightening. A knob or lever on the
ratchet allows the user to switch directions.
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Figure 9–9 A typical flex handle used to rotate a socket, also called a breaker bar because
it usually has a longer handle than a ratchet and therefore, can be used to apply more torque
to a fastener than a ratchet.

A ratchet turns the socket in only one direction and allows the
rotating of the ratchet handle back and forth in a narrow space.
Extensions and universal joints are used with sockets to allow
access to fasteners in restricted locations. Sockets are available
in various drive sizes, including 1/4-inch, 3/8-inch, and 1/2-inch.
Continued
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Figure 9–10 The most commonly used socket drive sizes include 1 /4 -inch, 3 /8 -inch, and
1 /2 -inch drive.

Many heavy-duty truck and/or industrial applications use 3/4 and
1-inch sizes. The drive size is the distance of each side of the
square drive. Sockets and ratchets of the same size are designed to
work together.
Continued
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Figure 9–11 A six-point
socket fits the head of the
bolt or nut on all sides. A
twelve-point socket can
round off the head of a
bolt or nut if a lot of force
is applied.

Right to Tighten
It is sometimes confusing which way to rotate a wrench or screwdriver,
especially when the head of the fastener is pointing away from you. To
help visualize while looking at the fastener, say “righty-tighty, lefty-loosey.”

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Crowfoot Sockets A crowfoot socket is a socket that is an openend or line wrench to allow access to fasteners that cannot be
reached using a conventional wrench. Crowfoot sockets are
available in the following categories:

Fractional inch openend
Metric open-end
Fractional line
Metric line

Figure 9–12 A crowfoot socket is designed to reach fasteners using a ratchet or breaker bar
with an extension.
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Torque Wrenches Socket turning handles designed to apply a
known force to the fastener are called Torque wrenches. A
clicker-type torque wrench is set to the specified torque and
“clicks” when the value has been reached.

When force is removed
from the handle, another
click is heard. The wrench
should be set back to zero
after use and check for

calibration regularly.

Figure 9–13 Using a torque wench to tighten
connecting rod nuts on an engine.
Continued
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Figure 9–14 A beam-type torque wrench that displays the torque reading on the face of the
dial. The beam display is read as the beam defects, which is in proportion to the amount of
torque applied to the fastener.

A beam-type torque wrench is used to measure torque. Instead of
presetting the value, the actual torque is displayed on the dial as the
fastener is tightened. Beam-type wrenches are available in 1/4, 3/8,
and 1/2 inch drives, in English and metric units.

Continued

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Check Torque Wrench
Calibration Regularly

Torque wrenches should be checked
regularly. For example, Honda has
a torque wrench calibration setup at
each of their training centers. It is
expected that a torque wrench be
checked for accuracy before every
use. Most experts recommend that
torque wrenches be checked and
adjusted as needed at least every
year and more often if possible.
Figure 9–15 Torque wrench calibration
checker.

Continued
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Is it Lb-Ft or Ft-Lb or Torque?
The unit for torque is expressed as a force times the distance (leverage)
from the object. Therefore, the official unit for torque is lb-ft (pound-feet)
or Newton-meters (a force times a distance). It is commonly expressed in
ft-lbs and even some torque wrenches are labeled with this unit.

Double-Check the Specifications
Misreading torque specs is easy to do but can have serious damaging
results. Specs for fasteners are commonly expressed lb-ft. Many smaller
fasteners are tightened to specifications expressed in lb-in.
1 lb-ft = 12 lb-in.
If a fastener were accidentally tightened to 24 lb-ft instead of 24 lb-in., the
actual torque applied will be 288 lb-in. instead of the specified 24 lb-in. The
extra torque will likely break the fastener, but it could also warp or distort
the part being tightened. Always double-check the torque specs.
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Safe Use of Sockets and Ratchets Always use the proper size
socket that correctly fits the bolt or nut. All sockets and ratchets
should be cleaned after use before being placed back into the
toolbox. Sockets are available in short and deep well designs.
Select the appropriate drive size.
For small work, such as on the
dash, select a 1/4-inch drive. For
most general work, use a 3/8.
For suspension, steering and
other large fasteners, use a 1/2inch drive.
When loosening, pull toward
yourself.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Figure 9–16 Deep sockets allow access to
the nut that has a stud plus other locations
needing great depth, such as spark plugs.

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Use Socket Adapters with Caution
Socket adapters are available and can be used for different drive size
sockets on a ratchet. Combinations include:
1 /4 -inch drive — 3 /8 -inch sockets
3 /8 -inch drive — 1 /4 -inch sockets
3 /8 -inch drive — 1 /2 -inch sockets
1 /2 -inch drive — 3 /8 -inch sockets
Using a larger drive ratchet or breaker bar on a smaller size socket can
cause the application of too much force to the socket, which could crack
or shatter. Using a smaller size drive tool on a larger socket will usually
not cause any harm, but would greatly reduce the amount of torque that
can be applied to the bolt or nut.

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Avoid Using “Cheater Bars”
Whenever a fastener is difficult to remove, some technicians will insert the
handle of a ratchet or a breaker bar into a length of steel pipe. The extra
length of the pipe allows the technician to exert more torque than can be
applied using the drive handle alone. However, the extra torque can easily
overload the socket and ratchet, causing them to break or shatter, which
could cause personal injury.

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SCREWDRIVERS
Many smaller fasteners are removed and installed by using a
screw-driver, available in many sizes and tip shapes.
The most commonly used is
called a flat tip or straight
blade.
Flat-tip screwdrivers are sized
by the width of the blade.
This width should match the

width of the slot in the screw.
Continued
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

Figure 9–17 A flat-tip (straight blade)
screwdriver. The width of the blade should
match the width of the slot in the fastener.

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CAUTION: Do not use a screwdriver as a pry tool or as a chisel. Always
use the proper tool for each application.

Another type of commonly used screwdriver is named for Henry
F. Phillips, who invented the crosshead screw in 1934. Due to the
shape of the screw and screwdriver, a Phillips screw can be driven
with more torque than a slotted screw.
A Phillips head screwdriver is specified by the length of the
handle and size of the point at the tip.
A #1 tip has a sharp point, a #2 the most commonly used. A #3 tip
is blunt and used for larger sizes of Phillips head fasteners.
Both straight and Phillips screwdrivers are available with a short
blade and handle for access to fasteners with limited room.
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