© 2012 delmar, cengage learning measuring tools and systems chapter 6

© 2012 Delmar, Cengage Learning

Measuring Tools and Systems

Chapter 6


Objectives• Perform measurements using any of the tools in

this chapter• Have a working understanding of the metric and

English systems of measurement


Introduction• Automotive technicians must understand

– British Imperial (U.S.) system• Based on inches, feet, and yards

– Metric system• American manufacturers have changed their

tooling to the metric system to be competitive

• Technicians working on domestic automobiles – Need to understand both systems


Metric System• Known as the international (S.I.) system

– Measurement of volume is the liter

– Unit of weight is the gram

– Metric equivalent to pounds is kilograms

– Psi and kilograms per square centimeter measure atmospheric pressure at sea level

– Temperature measured in degrees centigrade

– Torque readings are expressed in Newton-meters

• English system: foot-pounds


Metric System (cont'd.)• Metric system based on the number ten

– Very easy system to use• 1/100 (0.01) of a meter is a centimeter (cm)• 1,000 meters is a kilometer (km)• 1/1000 (0.001) of a meter is a millimeter (mm)

– Convert inches to millimeters• Multiply by 25.4

– Convert millimeters to inches • Divide by 25.4


Measuring Tools• Include:

– Steel rule: used to make approximate measurements

– Rulers: measure in metric and fractions of one inch

– Metric ruler: indicates hundredths and thousands of a meter

– Thickness gauges (i.e., feeler gauges): measure valve clearance, piston ring side clearance, etc.

– Plastigage: used to measure oil clearance in bearings and oil pumps


Precision Measuring Tools• Vernier calliper

– Developed in the 17th century

– Movable scale runs parallel to a fixed scale

– Measures outside diameter (O.D.) and inside diameter (I.D.)

• Main scale: divided into inches• Vernier scale: divides each .025” section on main

scale into 25 parts

– Measurement combines vernier scale and main scale readings


Micrometer• Several advantages

– Clear and easy to read

– Measure consistently and accurately

– Built-in adjustment to compensate for wear

• Reading a micrometer– One revolution of thimble advances or retracts

the spindle 1/40”

– Each line on the barrel represents 0.025”

– A new line is uncovered each thimble revolution

– Some also have a vernier scale


Metric Micrometer• Features

– One turn of thimble turns spindle 0.5 mm

– Hub graduated in millimeters

– Thimble has 50 divisions

– Read in the same manner as English counterpart

– Vernier scale reads to 0.002 mm

– Only five divisions


Combination Digital Mikes and Specialty Micrometers

• Combination digital mikes– Give both metric and English readings

– LCD readings taken from the digital readout window accurate to 0.0001

• Convertible between inch and metric

• Specialty micrometers– Several types

• Example: ball micrometer


Inside Micrometers• Used to measure:

– Cylinder bores

– Main and rod bearing bores

• Thimble does not move as freely on the barrel as the thimble of an outside micrometer– Added friction helps keep the reading from

changing

• Use extension rods to make them the proper size

• Have handles for use in deep cylinders


Telescoping and Split-Ball Gauges

• Work in cylinders smaller than about two inches– Known as transfer gauges

• Split-ball gauge – Used on small holes such as valve guides

• Telescoping gauges – Used with micrometers

– Measure cylinders, bearing bores, etc.


Dial Indicators• Used to measure:

– Movements• End play of crankshaft• Valve guide wear

– Valve-in-head depth

– Cylinder and bearing bores

• Comparison instruments– Measurements compared against known

measurement

© 2012 delmar, cengage learning measuring tools and systems chapter 6

Documents

cengage learning slide

cengage learning metric

vernier scale slide

cengage learning objectives

ball micrometer slide

inches vernier scale

metric specialty micrometers

metric micrometer features