Machine Shop Inspection Tools
By Kristen Rice
Updated September 26, 2017
Little is known about the machining industry by the general public. Many people do not take the time to realize that almost everything we use on a daily basis has come from a machine shop. The inside of writing pens, components in ovens and light fixtures were made in machine shops, and all were inspected with various types of inspection tools. Some are basic and easy to use while others take time and practice to master. They all serve the same purpose; to ensure quality product to the consumer.
Micrometers are a needed asset in any machine shop. They come with a digital read out, or veiner, with the measurement markings etched into the handle of the micrometer. Micrometers are used for measuring the outer diameter of parts with round outer diameters, and to read very small tubular parts, such as screws and tubing. Micrometers can also be used to determine the width of a part. The most commonly used micrometers are 0/1-, 1/2-, and 2/3-inch read-outs. Micrometers are very touchy tools that need to be handled with care. Calibrating a micrometer with a set block should be performed every day prior to use.
Calipers are found in every machine shop. Calipers come in both dial and digital types. They can be three-, six-, eight-inch or a foot long. Calipers are used to measure the length or width of a part, and can be used to measure the distance of the edge of part to the center. There is a rod that protrudes from the base of the caliper that can be used to measure the depth of a hole or to fit in tight areas to find the length from the lip to edge.
Height gages measure the overall distance of a measurement. The readings can be read digitally or from a dial indicator. To use a height gage, it must first be zeroed out on a set point, usually the top of the part. After it has been zeroed out, it is then dialed down until the "foot" lightly touches the part. Height gages are used to measure longer parts that cannot be measured by a caliper.
Depth gages are a type of caliper. They are identified by the anvil shaped handle and the extension rods that protrude when the spindle is twisted. Depth gages are used for measuring the distance of a hole and can be used to measure distance to shoulder.
Bore gages are used for measuring the inner diameter of a bored hole. They are commonly used with micrometers to get an accurate reading of a bored hole. Bore micrometers are also used while the material is still inside the machine, after the center of the hole is drilled but before the bore bar comes in, to assure adequate clearance.