Mechanical micrometers are instruments for precision dimensional gaging consisting of a ground spindle and anvil mounted in a C-shaped steel frame.  They are available in Vernier scale, digital and dial variations. Micrometers provide precise, quantitative measurements of a product's or component's attributes such as thickness, depth, height, length, I.D., O.D., roundness or bore.

Specialized micrometers are available for the measurement of threads, gear teeth and tube wall thickness.  Noncontact laser micrometers are also available. Laser micrometers are especially effective in inline gaging applications of high speed materials.

Types of Micrometers

Common micrometer types include external, internal, bore, height, laser, micrometer head, and thread.

• External micrometers are capable of measuring an outer diameter (OD) or outside feature of a part or component.
• Internal micrometers are capable of measuring an inner diameter (ID) or inside feature or cavity of a part or component.
• Bore micrometers have the ability to measure the inside diameter of a hole, bore, or blind hole at shallow to very deep (~0.03m inches to several feet) depths into the bore.
• Height micrometers are tailored for height measurement.
• Laser micrometers use optical, laser, or video-based technology to measure dimensional features.
• Micrometer heads or jig borer micrometers consist only of the spindle and drum portion (no frame or anvil). They are built into microscopes, machine tools, medical equipment or other metrological systems to provide precision measurement or positioning. Jig borer micrometers and end measuring rods (fixed standard) are commonly used to set spacing and table locations.
• Thread micrometers are designed for measuring thread size, pitch, or other parameters.

Micrometers can be available in sets of several gages and accessories packaged into a kit usually in a case with adjusting tools. Tool kits sometimes contain alternate extensions and contact tips, holders, bases, or standards. 

Specifications

Important parameters to consider when specifying micrometers include range and resolution. The range of the micrometer is the total range length or dimensional range that the gage can measure. The resolution is the best or minimum resolution for gages with digital displays. Measurement units for micrometers can be either English or metric with some being configured to measure both. The display can be non-graduated meaning that the micrometer has no display, dial or analog, digital display, column or bargraph display, remote display, or Vernier scale. 

Features

Micrometers come with cylindrical anvils and spindles with flat carbide or hardened steel contacting faces. Specialized anvils or spindles are also available, these include ball anvil, blade or spade anvil, flange of disc (gear tooth), pin or reduced face, point anvil (thread gaging), or v anvil or 3-point. Mounting options for micrometers include:

• Handheld or portable
• Machine mounted
• Benchtop or floor
• Automatic or inline

Micrometers may be supplied with plastic, heat insulating handles or holders. The insulating handles help prevent measurement errors in the gage that could be caused by the heat from a human hand. Machine travel enabled micrometers are typically mounted on a machine or are built into a product including machine tools, microscopes, and other instruments requiring precision dimensional measurement or position control. 

Standards 

A-A-58075 - Holder: Countersink, Adjustable Micrometer Stop

ASME B89.1.13 - Micrometers

BS 1734 - Specification for Micrometer Heads

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ValueTronics International, Inc.