Micrometer : Types

Basic types
The image shows three common types of micrometers; the names are based on their application:

* Outside micrometer (aka micrometer caliper), typically used to measure wires, spheres, shafts and blocks.

* Inside micrometer, used to measure the diameter of holes.

* Depth micrometer, measures depths of slots and steps.

* Bore micrometer, typically a three-anvil head on a micrometer base used to accurately measure inside diameters.

* Tube micrometer, used to measure the thickness of tubes.


Specialized types

Each type of micrometer caliper can be fitted with specialized anvils and spindle tips for particular measuring tasks. For example, the anvil may be shaped in the form of a segment of screw thread; in the form of a v-block; in the form of a large disc; etc.

Universal micrometer sets come with interchangeable anvils: flat, spherical, spline, disk, blade, point, knife-edge, etc. The term universal micrometer may also refer to a type of micrometer whose frame has modular components, allowing one micrometer to function as outside mic, depth mic, step mic, etc (often known by the brand names Mul-T-Anvil and Uni-Mike).

Blade mics have a matching set of narrow tips (blades). They allow, for example, the measuring of a narrow o-ring groove.

Pitch-diameter mics have a matching set of thread-shaped tips for measuring the pitch diameter of screw threads.

Limit mics have two anvils and two spindles, and are used like a snap gauge. The part being checked must pass through the first gap and must stop at the second gap in order to be within specification.

Micrometer stops are essentially inside mics that are mounted on the table of a manual milling machine or other machine tool, in place of simple stops. They help the operator to position the table precisely.
source :http://en.wikipedia.org/wiki/Micrometer#Types