Selecting an Inside Micrometer on Amazon.com
An inside micrometer, also known as an internal micrometer, is a precision instrument for measuring the inside dimension of an object, such as the diameter of a hole or the width of a groove. Though they both take the same kind of measurements, micrometers are adjusted via a screw mechanism while calipers use a pivot point or a slide mechanism. A caliper inside micrometer measures with a pair of movable jaws, while tubular- or rod-style inside micrometers use cylinders or rods with horizontal extensions. The measuring range and resolution or graduations of an inside micrometer vary from tool to tool. Some instruments include a set of interchangeable tubes or rods to provide a wide range of measurements. Inside micrometers show readings on a vernier scale, a digit counter, or a digital readout in metric, inch, or both metric and inch units. Some models have more than one type of reading display. Manufacturers include Mitutoyo and Starrett.