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Difficulty: MediumPrecision Measurement Instruments

An automotive machinist is selecting specialized precision measuring tools during an engine overhaul. Which inspection task correctly matches each precision measurement instrument?

  • Dial bore gaugeInspecting internal cylinder bore taper and out-of-round wear at various depths
  • Depth micrometerMeasuring the distance from the cylinder block deck down to the piston crown
  • Feeler gauge (thickness gauge)Measuring piston ring end gap seated inside a cylinder sleeve
  • Plastigage stripDetermining crankshaft journal-to-bearing oil clearance during cap assembly

Answer

Dial bore gauge matches cylinder bore taper and out-of-round inspection; Depth micrometer matches measuring deck-to-piston crown distance; Feeler gauge matches measuring piston ring end gap; Plastigage strip matches determining journal-to-bearing oil clearance.
Each instrument is paired with its specific geometric capability: dial bore gauges measure internal bore dimensions at depth; depth micrometers reference a flat surface to measure recessed depths; feeler gauge leaves measure narrow accessible gaps; and Plastigage measures assembled bearing journal clearances via controlled deformation.

Step-by-Step Solution

1
Identify the instrument designed for internal cylindrical geometry variation across depth.
The dial bore gauge directly measures internal bore diameters and reveals taper and out-of-round wear.
Internal cylinder walls require a long-reach indicator with centralizing contacts to inspect multiple heights within the bore.
2
Identify the tool designed for linear downward displacement from a reference plane.
The depth micrometer provides exact linear measurements from the block deck plane down to the piston crown.
Its precision flat reference base spans the opening while the micrometer spindle measures downward distance.
3
Identify the tool designed for narrow clearance gap measurement between parallel metal faces.
The feeler gauge blade set measures piston ring end gap.
Thin calibrated steel leaves slide into narrow gaps to verify clearances within thousandths of an inch.
4
Identify the consumable precision gauge used for clamped journal oil clearances.
Plastigage determines journal-to-bearing shell clearance upon cap torquing.
The plastic thread deforms proportionally to available clearance when clamped without rotating the crankshaft.

Key Concept

Selection and application of precision automotive measuring instruments based on component geometry and tolerance type.
Estimated Time:1m 0s
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Topics

Precision Measurement Instruments

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