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Chapter 8: B. Special Gages and Applications 83Table 8.1 Summary of commonly used gages and their applications. ContinuedGageWorking gageInspection gageReference ormaster gageLimit gageRing gagePlug gageSnap gageSpline gageScrew-threadmicrometersTemplateScrew-pitch gageOscilloscopeMultimeterPyrometerPneumatic gageOptical flatsMachine visionX-ray systemsUses and applicationsUsed by the machine operator or shop inspector to check the dimensionsof parts as they are being produced. They usually have limits based on thepiece being inspected.Used by personnel to inspect purchased parts when received, ormanufactured parts when finished. These gages are designedand manufactured so as not to reject any product previously acceptedby a properly designed and functioning working gage.Used for checking the size or condition of other gages, and represent asexactly as possible the physical dimensions of the product.Often called a go/no-go gage, establishes the high and low limitsprescribed by the tolerance on a dimension. A limit gage may be eitherdouble-end or progressive.Used for checking outside dimensions such as the limit sizes of around shaft.Used for checking inside dimensionsA fixed gage with the gauging members specially arranged for measuringdiameters, thickness, and lengths.An instrument for inspecting splined workpieces prior to assembly.Designed to measure threads within a narrow range of pitches.Used to control or gauge special shapes or contours in manufactured parts,or check a specified profile.Used to check the pitch of a screw.Troubleshooting electronic equipment failure by graphically showingsignals that indicate failure or malfunction.An electronic gage that combines more than one function in a singleunit. Multimeters use either analog or digital displays. Common usesinclude fault discovery, fieldwork of electronic or telecommunicationstechnicians, or as a basic workshop instrument. Standard measurementstaken using a multimeter include voltage, current, and resistance.A noncontact instrument for measuring an object’s temperature bymeasuring its self-emission and emissivity.Used for measuring, comparing, or checking dimensions by sensing theflow of air through the space between a gage head and workpiece surface.Often used to test the flatness of surfaces. The presence of interferencebands between the flat and the surface being tested is an indication thatthe surface is not parallel with the surface of the flat.Used for inspection of manufactured products such as semiconductorcomponents and automotive parts as well as in medical applications.Used in nondestructive testing and inspection of electronic assemblies,especially printed circuit boards.Part II.B.3

Chapter 9C. Gage Selection, Handling,and UsePart II.C.11. FACTORS IN GAGE SELECTIONSelect gages according to the featureor characteristic to be measured, theapplicable tolerance, the 10:1 rule, etc.; theaccuracy, resolution, and capability of thetest instrument, and determine whetherthe type of measurement should be direct,differential, or transfer. (Application)Body of Knowledge II.C.1There are many factors to consider in the selection of a measuring or gauginginstrument or system for a particular manufacturing inspection operation.The Rule of TenThe rule of ten—sometimes referred to as the 10:1 rule or the gage maker’s rule—serves as a baseline or beginning of the selection process. It states that inspectionmeasurements should be better than the tolerance of a dimension by a factor of10, and calibration standards should be better than inspection measurements bya factor of 10.For example, assuming that the tolerance on a shaft diameter is ±0.025 mm(±.0010 in.), the increment of measurement on the inspection instrument shouldbe as small as 0.025/10 = 0.0025 mm (.00010 in.).Similarly, the increment of measurement of the calibration standard for theinspection instrument should be as small as 0.0025/10 = 0.00025 mm (.00010 in.).Once the smallest increment of measurement for an instrument has been determined,then candidate instruments need to be evaluated in terms of the degree ofsatisfaction they offer relative to the following performance criteria:1. Accuracy. The ability to measure the true magnitude of a dimension.84

Chapter 8: B. Special Gages and Applications 83

Table 8.1 Summary of commonly used gages and their applications. Continued

Gage

Working gage

Inspection gage

Reference or

master gage

Limit gage

Ring gage

Plug gage

Snap gage

Spline gage

Screw-thread

micrometers

Template

Screw-pitch gage

Oscilloscope

Multimeter

Pyrometer

Pneumatic gage

Optical flats

Machine vision

X-ray systems

Uses and applications

Used by the machine operator or shop inspector to check the dimensions

of parts as they are being produced. They usually have limits based on the

piece being inspected.

Used by personnel to inspect purchased parts when received, or

manufactured parts when finished. These gages are designed

and manufactured so as not to reject any product previously accepted

by a properly designed and functioning working gage.

Used for checking the size or condition of other gages, and represent as

exactly as possible the physical dimensions of the product.

Often called a go/no-go gage, establishes the high and low limits

prescribed by the tolerance on a dimension. A limit gage may be either

double-end or progressive.

Used for checking outside dimensions such as the limit sizes of a

round shaft.

Used for checking inside dimensions

A fixed gage with the gauging members specially arranged for measuring

diameters, thickness, and lengths.

An instrument for inspecting splined workpieces prior to assembly.

Designed to measure threads within a narrow range of pitches.

Used to control or gauge special shapes or contours in manufactured parts,

or check a specified profile.

Used to check the pitch of a screw.

Troubleshooting electronic equipment failure by graphically showing

signals that indicate failure or malfunction.

An electronic gage that combines more than one function in a single

unit. Multimeters use either analog or digital displays. Common uses

include fault discovery, fieldwork of electronic or telecommunications

technicians, or as a basic workshop instrument. Standard measurements

taken using a multimeter include voltage, current, and resistance.

A noncontact instrument for measuring an object’s temperature by

measuring its self-emission and emissivity.

Used for measuring, comparing, or checking dimensions by sensing the

flow of air through the space between a gage head and workpiece surface.

Often used to test the flatness of surfaces. The presence of interference

bands between the flat and the surface being tested is an indication that

the surface is not parallel with the surface of the flat.

Used for inspection of manufactured products such as semiconductor

components and automotive parts as well as in medical applications.

Used in nondestructive testing and inspection of electronic assemblies,

especially printed circuit boards.

Part II.B.3

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