7.3.11 Micrometer Flashcards
What is needed for precise measurement to the second decimal place in the metric system?
A more accurate method of measurement, such as a vernier calliper or a micrometer.
What are the four types of micrometers?
- Internal (inside) micrometer
- External (outside) micrometer
- Depth micrometer
- Thread micrometer
What is the basic structure of a micrometer?
A semi-circular frame with a cylindrical extension (barrel) at its right end, and hardened anvils inside at the left end.
What function does the spindle lock serve in a micrometer?
It allows the user to measure something remotely or at arm’s reach, lock it, and then bring it closer to view.
How does a metric micrometer measure?
The bore of the barrel is screwed 0.5 mm pitch, and the spindle screws through it.
What is the range of a metric micrometer?
The range is 25 mm, requiring six micrometers to measure up to 150 mm.
How does an imperial micrometer advance the spindle?
One revolution of the thimble advances the spindle face precisely 1/40 inch or 0.025 inch.
How is the reading line on the sleeve of an imperial micrometer divided?
It is divided into 40 equal parts, corresponding to the number of threads on the spindle.
What does every fourth line on the imperial micrometer reading line represent?
Every fourth line designates a hundred thousandths.
How can the accuracy of a micrometer be checked?
By using a standard or gauge block to adjust the zero-mark on the thimble to coincide with the sleeve datum line.
What does an internal micrometer measure?
It is designed to measure the inner diameter of holes.
What is the purpose of a three-point internal micrometer?
To provide more accuracy to internal measurements of bores.
What does a depth micrometer measure?
It measures the depth relative to a base plate that is ground and square to the spindle axis.
How are micrometer readings taken in metric?
Add the number of hundredths indicated on the thimble to the millimetres and half-millimetres uncovered on the barrel.
What is the reading example for a metric micrometer?
Reading = 8.86 mm
Calculation: 8.00 (from thimble) + 0.50 (half mm) + 0.36 (thimble lines)
How are micrometer readings taken in imperial?
Add the number of thousandths indicated on the thimble to the tenths and hundredths uncovered on the barrel.
What is the reading example for an imperial micrometer?
Reading = 0.362 in
Calculation: 0.300 (from thimble) + 0.050 (additional divisions) + 0.012 (thimble lines)
What is required for enhanced accuracy in micrometer measurements?
A micrometer with an accuracy of 0.001 mm or 0.0001 inch, which includes an extra vernier scale.
What should be checked before handling a micrometer?
- Pre-use checks
- Calibration sticker
- Obvious damage
- Zero setting
What is the correct way to set a micrometer for measurement?
Set the micrometer to an oversize dimension and clamp the spindle against the subject using the ratchet stop.
