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Home » Laboratory Equipments » Physics Lab Equipment » Micrometer

Micrometer




MicrometerA Micrometer is basically a measuring instrument. A Micrometer is also known by another name and that of Micrometer Screw Gauge. As compared to a Calliper it provides a greater accuracy but measures a smaller range of lengths.

With a Micrometer the thickness of blocks, depths of slots or diameters(both I.D and O.D) of shafts can be easily measured along with length roundness or bore. Mechanical micrometers in the form of Vernier scale or with digital and dial variations are quite popular. In a physics lab both Inch Micrometer and Metric Micrometer are used. In case a metric or inch micrometer is used without vernier then smaller measurement readings than those graduated, can be got by a visual interpolation between the graduations.

Do You Know?
The Micrometer was invented by William Gascoigne (1612 – 1644) an English astronomer and a mathematician. Initially William Gascoigne used the Micrometer to measure the distances between stars. Only later on was the Micrometer adapted for measuring small dimensions.
If a vernier scaled is added to the ordinary Micrometer it is called a Vernier Micrometer. With the addition of a vernier to a Micrometer, taking precise readings of one ten-thousandth of an inch becomes distinctly possible. The vernier markings appear on the sleeve of a micrometer. They are infact parallel to the thimble markings.

How to Select the Right Micrometer
Selecting the appropriate Micrometer is a challenging task especially if there is a wide range of items that need to be measured. Some of the broad points to be considered is given here.
Parts of a Micrometer

Parts of a Micrometer

Some of the major parts of a Micrometer is described here.
Anvil : It is the part toward which the spindle moves. The measurable object rest against an Anvil.

Spindle : Spindle is a cylindrical part which makes a push towards the anvil by the action of a thimble.

Thimble : The component that one's thumb turns.

Frame : Frame is a typically a C-shaped body. Its use is for holding the anvil as well as the barrel in constant relation with each other. The thick shape of the frame is for minimizing flexion, expansion, and contraction, than can distort the Micrometer.

Lock Ring : Lock-ring is essentially the knurled part. It can be tightened for holding the spindle stationary, to say for momentarily keeping a measurement on hold.

Rachet : The Rachet is turned clockwise for perfectly trapping the object to be measured in between an anvil face and the spindle face. On perfect tightening the Rachet makes a clicking’ noise indicating that the reading of the measurement can now be taken.

Types of Micrometer
Outside MicrometerOutside Micrometer
An outside micrometer is for typically measuring the external dimensions of objects such as shafts, wires, spheres, blocks etc. Outside Micrometers are also known as External Micrometers.


Inside MicrometerInside Micrometer
The Inside micrometer is used for measuring accurately and conveniently the openings of holes or cavities. Internal micrometers are quite adept in measuring the inner diameter (ID) or an inside feature of a part or component.


Depth MicrometerDepth Micrometer
In Depth Micrometer a spindle is projected via a flat and precisely machined bar. Depth Micrometres are typically used for measuring accurately the inside diameter of holes, slots, bores or recesses to within 0.001 of an inch.

Digital MicrometerDigital Micrometer
Digital Micrometer is appropriate for applications where the requirement is to record accurately the absolute position or differences between two or more positions. The object that is to be measured is made to fit in between the metal rods positioned to the left of the digital display.

Some of the features to look for in latest range of Digital Micrometers include