LO 5-2 Identify and explain the types and standards involved in making precision measurements

1. Types of Precision Measurement

Types of Precision Measurement

Precision measuring tools have been developed to compensate for the inaccurate estimation of linear distances, clearances, or thicknesses using line-graduated measuring tools (such as rulers or measuring tapes) or dependency on the sense of sight and touch to take measurements. Measuring methods range from simple mechanical-type devices from a ruler or micrometer to dial or digital vernier calipers, optical, electronic, and even electronic measuring instruments that use wireless Bluetooth communication to transmit and store measurement data. It is important to point out that many technicians, even after years of experience, overestimate their ability to accurately approximate measurements, such as bearing clearances in wheel ends, turbocharger shafts, or the width of a rocker lever to valve stem clearances using sight or sense of touch. Commonly used precision measuring tools enable precise measurement of critical clearances, linear distances, thickness, roundedness or concentricity, hydraulic and gas pressure, radiuses, component weight, fastener torque, engine speed, depth, taper wear, thread pitch, and operating tolerances. Other precision tools related to engine work (available but infrequently used in a repair and maintenance facility) include devices that measure the surface roughness of sealing surfaces, hardness of material, and angles.

These next sections will examine the units of precision measurement and the purpose, construction, and use of common categories of precision measuring tools used or encountered by technicians.