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A micrometer is a precision measuring tool used to measure very small dimensions with high accuracy. It is commonly used in mechanical engineering, machining, and manufacturing for tasks requiring precision measurements. Outside Micrometers are used for measuring the thickness or outside diameter of small parts. They are industry standard measuring tools because of their high accuracy/resolution and ease of use. OD micrometers are available in a variety of different spindle and anvil configurations to allow the operator to measure difficult-to-reach features on a workpiece.
Diagram of a Micrometer
Diagram of a Micrometer
Mechanical Outside Micrometers
Mechanical Outside Micrometers
Mechanical Outside Micrometers, also known as micrometer, mics or screw gages, measure ranges are from 0" to 20" engineered in 1" steps (lengths). They are graduated in 0 .001" with a 0.0001" vernier and available in metric sizes and graduations.
Outside micrometers are available in a variety of spindle and anvil configurations to allow the operator to measure difficult-to-reach features on a workpiece. The measuring range on a typical OD micrometer is 1" (25mm). Some special application micrometers have a smaller or greater range than 1" (25mm). Wide range OD micrometers (interchangeable anvil micrometers) are available and reduce the cost of a micrometer set, versus the cost of individual micrometers to cover the same range (typically a 6" range).
How to Read a Micrometer:
How to Read a Micrometer:
The precision ground thread on the spindle is the basis for a micrometer’s high accuracy and resolution. An English micrometer spindle uses 40 TPI. One revolution of the spindle advances the measuring face by .025". The sleeve is graduated every .025" and the thimble is graduated every .001". In addition, the sleeve may also have a vernier scale that allows the operator to resolve the micrometer reading to .0001".
The micrometer sleeve is divided into forty equal parts. Each division is indicated by a vertical line that represents one-fortieth of an inch or .025". Each fourth line is marked by a longer line and a number which designates one hundred-thousandths. Example: The line on the sleeve marked "1" represents .100", the line marked "2" represents .200" and so forth.
The micrometer thimble is divided into twenty-five equal parts. One complete rotation of the thimble coincides with the smallest division on the sleeve. Thus, the division on the thimble is one-twenty-fifth of .025" or .001".
To read to one ten-thousandth requires an additional scale called the Vernier scale. In the case of a regular micrometer, the vernier consists of ten divisions, marked on the sleeve, which are spaced within nine divisions of the thimble scale. Each division on the vernier, therefore, is one-tenth shorter than that of the thimble's, thus representing .0001".
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