Download - Metrology of
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© Oxford University Press 2013. All rights reserved.
Chapter 8
Metrology of Gears
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Gears are the main elements in a transmission system. For efficient transfer of speed and power, it is needless to say that gears should conform perfectly to the designed profile and dimensions.
Misalignments and gear runout will result in vibrations, chatter, noise and loss of power.
On the other hand, threaded components should meet stringent quality requirements to satisfy the property of interchangeability.
Introduction
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METROLOGY OF GEARS
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Spur Gear Terminology
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Gear blank run‐out errors
Gear tooth profile error
Gear tooth errors
Pitch errors
Run‐out errors
Lead errors
Assembly errors
Errors in Spur Gear
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Runout
Pitch
Profile
Lead
Backlash
Tooth Thickness
Composite method of gear inspection
Measurement of Gear Elements
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In case of a gear, runout is the resultant of the radial throw of the axis of a gear due tothe out of roundness of the gear profile.
Measurement of Radial Turnout
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These instruments enable the measurement of chordal pitch between successive pair of teeth.
Pitch Measuring Instrument
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A pitch checking instrument is essentially a dividing head that can be used to measure pitch variations. The instrument can be used for checking small as well as large gears due to its portability.
Pitch Checking Instrument
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Gear Measuring Machine
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In case of spur gears, lead tolerance is defined as the allowable deviation across the face width of a tooth surface.
Measurement of Lead
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Measurement of Tooth Thickness
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Measurement of Tooth Thickness
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Any measurement made by gauging the span of number of teeth will be constant.
That is, AC = A1C1 = A2C2 = A0C0, where A0C0 is the arc length of base circle between the origins of involutes.
Measurement with Tooth Span Micrometer
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The micrometer is as good as an inspection gauge and can be used to check gears for accuracy of span width
Measurement with Tooth Span Micrometer
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It is one of the popular gear testing machines used in metrology laboratories and tool rooms. The gear being inspected will be made to mesh with a standard gear and a dial indicator is used to capture the radial errors.
Parkinson Gear Test