Precision Measuring and Layout Flashcards
6 cards from real Millwright Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Precision Measuring and Layout flashcards as text
What is the resolution of a standard metric outside micrometer with a thimble graduated in 0.01 mm divisions?
Answer: 0.01 mm
A standard metric micrometer reads to 0.01 mm resolution using the combination of the sleeve scale (0.5 mm divisions) and the thimble scale (0.01 mm divisions around the circumference).
When using a dial indicator to check shaft runout, what does a Total Indicator Reading (TIR) of 0.05 mm mean?
Answer: The maximum indicator deflection from lowest to highest reading during one full rotation is 0.05 mm
TIR (Total Indicator Reading) is the difference between the maximum and minimum dial indicator readings during one complete shaft rotation, representing the total runout of the surface being measured.
What is the proper technique for measuring with a telescoping gauge?
Answer: Compress, insert into the bore, lock at the correct contact feel, then measure the gauge with a micrometer
Telescoping gauges are transfer instruments: the plungers are compressed, inserted into the bore, then gently rocked to find the maximum diameter contact point, locked, withdrawn, and measured with a micrometer.
Why must precision measuring instruments be allowed to equalize to the same temperature as the workpiece before measuring?
Answer: Thermal expansion causes dimensional changes that create measurement errors
Metals expand and contract with temperature changes. If the instrument and workpiece are at different temperatures, their dimensions will differ from their nominal values, causing measurement errors that can exceed tolerances.
What is a surface plate used for in precision layout and measurement?
Answer: As a flat reference plane for layout work, height measurements, and checking flatness of components
A surface plate provides an extremely flat reference plane (typically granite, lapped to within micrometers) used as a datum surface for layout work, height gauge measurements, and checking component flatness.
When using vernier calipers, what is the most common source of measurement error?
Answer: Excessive jaw pressure causing deflection, or not measuring at the correct point on the jaws
The most common errors with vernier calipers include applying too much thumb pressure (causing jaw deflection and an undersized reading), measuring with the jaw tips instead of the flat measuring surfaces, and parallax when reading the scales.