What are micrometers?
A micrometer (sometimes called micrometer screw gauge) is a precision measuring instrument, used to obtain very fine measurements and available in metric and imperial versions. They use a calibrated screw or thread (found internally on the spindle) for precise measurement of components in mechanical engineering and machining as well as most mechanical trades. They usually come in the form of calipers e.g. opposing ends joined by a frame.
Micrometers are composed of:
• Frame - The C-shaped body that holds the anvil and barrel in constant relation to each other.
• Anvil - The shiny part that the spindle moves toward, and that the sample rests against.
• Sleeve / barrel / stock - The stationary round component with the linear scale on it, sometimes with vernier markings.
• Lock nut / lock-ring / thimble lock - The knurled component (or lever) that tightens to hold the spindle stationary.
• Spindle - The shiny cylindrical component that the thimble causes to move toward the anvil
• Thimble - The component that turns by using a person’s thumb. Graduated markings.
• Ratchet stop - Device on end of handle that limits applied pressure by slipping at a calibrated torque.
• Screw

How do they work?
The precision is determined by the thread pitch of the spindle. The spindle is a very accurately machined screw and the object to be measured is placed between the spindle and the anvil. The spindle is moved by turning the ratchet knob or thimble until the object to be measured is lightly touched by both the spindle and the anvil.

Types of Micrometers
• Outside micrometer: most common type used to measure external dimensions such as the outside diameter of an object.
• Inside micrometer; used to measure inside dimensions like the inside diameter of a hole or tube. There are two types: caliper-type and tubular and rod.
• Depth micrometer: these are used to measure the depths of holes, slots and steps. They come with a variety of interchangeable rods of different lengths so that they can be used to measure a range of depths.
• Provide very accurate measurements and are considered one of the most accurate types of measuring device.
• Ratchet speeder helps to provide reliable measurements.
• Integrated scales, the sleeve scale and thimble scale are built into the tool, another measuring instrument such as a ruler or tape measure is not required.
• Durability and long lasting and unlikely to need replacing or repairing

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Description Price Accuracy Resolution Imperial or Metric Micrometer Type SPC Data Output Data Processing Battery Operated Set Contents Metric-Imperial Conversion Maximum Measurement Minimum Measurement
RS Stock No. 572-561
Mfr. Part No.DW934
±0.01 mm - Metric Internal - - No Adjustment Tool, Measuring Rod, Micrometer Head - 300mm 50mm
RS Stock No. 572-555
Mfr. Part No.DW933
±0.0004 in - Both Internal - - No Adjustment Tool, Measuring Rod, Micrometer Head - 12in 2in
RS Stock No. 157-1187
Mfr. Part No.DY094
±0.002 mm - Metric External - - No - - 25mm 0mm
RS Stock No. 157-1171
Mfr. Part No.DY093
±0.0001 in - Imperial External - - No - - 2in 1in
RS Stock No. 157-1165
Mfr. Part No.DY092
±0.0001 in - Imperial External - - No - - 1in 0in