Caliper Assessment Vernier Measurement 3 — Questions and Answers
Question 1: If the zero of the vernier scale is to the LEFT of the zero of the main scale when the caliper is closed, the instrument has:
- Negative zero error (Correct answer)
- Positive zero error
- No zero error
- Backlash error
Correct answer: Negative zero error
When the vernier zero falls left of the main scale zero, the caliper reads less than the true value — this is negative zero error.
Question 2: A machinist measures the same part five times with a vernier caliper and gets: 12.14, 12.16, 12.14, 12.15, 12.15 mm. What is the average reading?
- 12.148 mm (Correct answer)
- 12.150 mm
- 12.140 mm
- 12.145 mm
Correct answer: 12.148 mm
(12.14+12.16+12.14+12.15+12.15) ÷ 5 = 60.74 ÷ 5 = 12.148 mm.
Question 3: Which vernier caliper graduation allows the finest possible resolution?
- 50-division vernier (0.02 mm) (Correct answer)
- 10-division vernier (0.1 mm)
- 20-division vernier (0.05 mm)
- 25-division vernier (0.04 mm)
Correct answer: 50-division vernier (0.02 mm)
A 50-division vernier yields the smallest least count of 0.02 mm among the common types listed.
Question 4: A technician corrects for a positive zero error of +0.06 mm. The uncorrected reading is 25.34 mm. What is the true measurement?
- 25.28 mm (Correct answer)
- 25.40 mm
- 25.34 mm
- 25.06 mm
Correct answer: 25.28 mm
True value = uncorrected reading − positive zero error = 25.34 − 0.06 = 25.28 mm.
Question 5: On an inch-based vernier caliper with 25 vernier divisions spanning 0.600 inch (main divisions = 1/16 in), what is the least count in inches?
- 0.001 in (Correct answer)
- 0.025 in
- 0.010 in
- 0.002 in
Correct answer: 0.001 in
Standard inch vernier calipers are typically graduated to 0.001 inch (25 divisions over 0.025 inch range).
Question 6: What is the purpose of the locking screw (or thumb screw) on a vernier caliper?
- To fix the slide in place so the reading doesn't change while the caliper is removed from the workpiece (Correct answer)
- To adjust the main scale zero
- To tighten the jaws on the workpiece
- To calibrate the vernier divisions
Correct answer: To fix the slide in place so the reading doesn't change while the caliper is removed from the workpiece
The locking screw holds the slider stationary so the measurement can be read after removing the caliper from the part.
Question 7: Which scenario would most likely INVALIDATE a vernier caliper measurement?
- Measuring a hot workpiece immediately after machining (Correct answer)
- Using the caliper in a 68°F room
- Cleaning the jaws before measurement
- Taking three repeated readings
Correct answer: Measuring a hot workpiece immediately after machining
Thermal expansion of a hot part will cause the measurement to differ from the part's true dimension at standard temperature (68°F/20°C).
Caliper Assessment Vernier Measurement 3
If the zero of the vernier scale is to the LEFT of the zero of the main scale when the caliper is closed, the instrument has: