The Starrett 458 series automotive disc brake micrometer has a deep-throated frame and pointed anvil for measuring wear groove depth in disc brakes. It also has a vernier scale in inch units for taking precise outside diameter (OD) measurements, a tapered frame for measuring narrow slots and tight places, and a ratchet-stop mechanism that helps provide uniform pressure for precise, repeatable measurements. The micrometer’s steel frame is perforated to help provide light weight with rigidity. The vernier scale on the thimble and sleeve is graduated to 0.001”, with a satin chrome rust- and glare-resistant finish. The spindle and anvil are carbide-tipped for wear resistance.

Micrometers are precision measuring instruments that use a calibrated screw to measure small distances. These measurements are translated into large rotations of the screw that are then able to be read from a scale or a dial. Micrometers are typically used in manufacturing, machining, and mechanical engineering. There are three types of micrometer: outside, inside, and depth. Outside micrometers may also be called micrometer calipers, and are used to measure the length, width, or outside diameter of an object. Inside micrometers are typically used to measure interior diameter, as in a hole. Depth micrometers measure the height, or depth, of any shape that has a step, groove, or slot.

The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company was founded in 1880 and is headquartered in Athol, MA.