What Are Micrometers Used for?
A micrometer is a measuring device typically used in machining and mechanical engineering to gauge or determine the precise length of a short object or sample. Also known as a micrometer screw gauge, most types of micrometers are calipers and are used alongside other metrological measuring instruments, such as vernier and dial calipers.
Other People Are Reading
-
Basic Types
-
There are five basic types of micrometers: outside, inside, depth, bore and tube. An outside micrometer, also called a micrometer caliper, is typically used to measure blocks, shafts, spheres and wires. An inside micrometer is used to measure the diameter of holes, while a depth micrometer is used to measure the depth of steps and slots. A bore micrometer has a three-anvil head attached to a micrometer base and is used to measure inside diameters accurately. Last but not least, the tube micrometer is used to measure the thickness of tubes.
Basic Parts
-
A basic micrometer is composed of a heavy C-shaped frame that holds the barrel and anvil in constant relation to each other and usually has a high thermal mass to prevent substantial heat increase, thereby protecting the fingers. It is also composed of the anvil and and a barrel. The anvil is a shiny part where the spindle moves toward and where the sample rests against. The barrel (also called stock or sleeve) is a round stationary part with a linear scale and markings.
-
Other Parts
-
The basic micrometer also has a lock nut (also known as a thimble lock or lock-ring), which serves as a lever that can be tightened to hold the spindle in place when holding a sample. The screw, which is found inside the barrel, is the heart of the micrometer and determines the precision of the measurement. Other parts include the spindle, thimble and ratchet stop. The spindle is a cylindrical part that the thimble causes to move toward the anvil. The thimble has graduated markings and is the part that the thumb turns when the basic micrometer is in use. Lastly, the ratchet stop is found at the end of the handle and it limits applied pressure through a calibrated torque.
Mechanism
-
At the heart of the micrometer is the screw with a threadform wherein the accuracy of the instrument is derived. An accurately made screw will produce accurate measurements. A particular object is measured by the amount of rotation that precisely correlates to the axial movement of the instrument and the screw's lead, which is known as the constant. The constant is the distance that the screw moves forward axially with a complete 360° turn. The amount of a given axial movement will be amplified with an appropriate diameter and lead of the screw, which results from the circumferential movement.
Operation
-
In older micrometers, the measurement can be read through the position of the thimble in the scale markings and shaft. To read a fraction of the smallest scale mark, a vernier scale is typically used alongside the micrometer for better precision. Newer models are digitalized and include an electronic readout display, which indicates the precise measurement on an LCD screen.
-
