MEASURING AND REPAIR INSTRUMENTS
You, as an Engineman, must he able to identify the
basic measuring and repair instruments and the basic
components of these instruments. This chapter will help
you to recognize the how and when to use and maintain
basic measuring and repair instruments and engine test
Measuring instruments are used to check tolerances
and specifications during inspections and repairs of
internal combustion engines and auxiliary equipment.
You, as an Engineman, need measuring instruments to
determine what parts are worn and need to be repaired
or replaced. The following measuring and repair
instruments are discussed in this chapter: dial indicator,
dial/vernier caliper, micrometer, snap gauge, bore
gauge, strain gauge, borescope, stroboscope, torque
wrench, multiplier, adapter, ridge reamer, cylinder hone,
SENSITIVE MEASURING TOOLS
Sensitive measuring tools are measuring devices
that provide measurement readings to a thousandth of
an inch or less. The more common sensitive measuring
tools you will use are the dial indicator, dial/vernier
caliper, micrometer, snap gauge, bore gauge, and strain
A dial indicator is used to measure shaft runout,
shaft thrust, gear backlash, flywheel face runout,
flywheel housing concentricity, and valve seat
concentricity. You can mount a dial indicator on a test
stand or, with clamps and a magnetic base, directly on
the equipment to be measured. Figure 2-1 shows a
typical dial indicator with mounting accessories,
Most dial indicators have components such as a
bezel, indicator pointer, tool post and clamp, magnetic
toolholder, and sensor button that are used in taking
The following procedures explain how to use the
indicator to take shaft runout and crankshaft end play
measurements. Procedures for taking other
measurements are similar.
Figure 2-1.Typical dial indicator wlth mounting accessories.
When you need to measure a shafts runout, select
a suitable position on the shaft, free of keyways,
corrosion, or other damage. Clean the surface and
remove any burrs around scratches or dents. To take the
runout measurement, use the following procedure:
1. Place the shaft in well-oiled V-blocks. If the
shaft is a crankshaft, place the bearing journals in the
2. Attach the magnetic base to a machined surface.
Mount the dial indicator on a tool mounting holder and
attach the holder to the base.
3. Adjust the mounting post so you can easily read
the face of the dial.