[IE 21] 1.5 - Measurement, Inspection, and Testing

Measuring and Inspecting

control and maintain the quality of a product

Inspection

examination of product during or after manufacture, manually or automatically

Attributes

Inspection: using gages to determine if the product is good or bad, resulting in a yes/no, go/no-go decision (e.g. low oil pressure warning light)

Variable

Inspection: using calibrated instruments to determine the actual dimensions of the product for comparison with the size desired (e.g. oil pressure gauge)

Measurement

generally accepted term for inspection by variables;

Unit of measurement

magnitude of the characteristic

Gauging

term for determining whether the dimension or characteristic is larger or smaller than the established standard or is within some range of acceptability

Allowance

intentional, desired difference between the dimensions of two mating parts

Clearance Fit

Allowance: largest shaft is smaller than the smallest hole; shaft to rotate or slide freely within the hole

Interference Fit

Allowance: the largest hole is smaller than the smallest shaft; shaft to be securely held within the hole

Transition Fit

Allowance: the shaft may either be larger or smaller than the hole; shaft to be held precisely, yet not so tightly that it can’t be disassembled

Tolerance

undesirable, but permissible, deviation from a desired dimension

Bilateral tolerance

Tolerance: plus or minus deviation from the nominal size

Unilateral tolerance

Tolerance: the deviation is in one direction from the nominal size

Limits

Tolerance: maximum and minimum dimensions that result from application of the designated tolerance

Machinist’s Ruler

Linear Measuring Instruments: precision measuring tool made of thin, flexible, or rigid tempered stainless steel

Vernier Caliper

Linear Measuring Instruments: end-measuring instrument, make both outside and inside measurements

Micrometer Caliper

Linear Measuring Instruments: make very fine measurements beyond the hundredths of a centimeter

Go-No Go Gauge

Gauges for Attributes Measuring: used to check a workpiece against its allowed tolerances

Plug Gauges

Gauges for Attributes Measuring: gauge internal dimensions

go plug gauge

Plug Gauges: controls minimum internal dimension

no-go plug gauge

Plug Gauges: controls maximum internal dimension

Ring Gauges

Gauges for Attributes Measuring: gauge shafts or other external round members

Thread Gauges

Gauges for Attributes Measuring: where the “bolts” (externally threaded parts) or the “nuts” (internally threaded parts) are to be quickly checked for acceptance