<Li> 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 . The two gaps accurately reflect the top and bottom of the tolerance range . </Li> <Li> Bore micrometer, typically a three - anvil head on a micrometer base used to accurately measure inside diameters . </Li> <Li> Tube micrometers have a cylindrical anvil positioned perpendicularly to a spindle and is used to measure the thickness of tubes . </Li> <Li> Micrometer stops are micrometer heads that are mounted on the table of a manual milling machine, bedways of a lathe, or other machine tool, in place of simple stops . They help the operator to position the table or carriage precisely . Stops can also be used to actuate kickout mechanisms or limit switches to halt an automatic feed system . </Li>

The thimble and barrel of a micrometer are marked with scales for