The Starrett 697Z Inside Dial Gauge has a range of measurement of 2-3/8 to 18" and can be used between two walls to check for parallelism and also to take comparative measurements of internal diameter. This direct-measuring gauge has marked rods that designate approximate overall length. The balance dial reads 0-20-0, and gradient spacing is 0.001". The indicator bezel is rotated to adjust the dial in relation to the hand and has a non-breakable crystal. The two-point contact system can be used to detect geometry problems such as ovality and taper. The tool can be set with a micrometer and comes with 10 rods and one extension.
Bore gauges measure holes, or bores, in a workpiece. They can measure the interior diameter of a hole at any depth, while internal micrometers can only measure to the depth of their teeth. Bore gauges are typically calibrated with a setting ring and come in two types: simple and direct-measuring. Simple bore gauges are used with a caliper to transfer the hole measurement, while the more complex gauges take the measurement directly, and display it through a vernier, dial, or digital display. Bore gauges have a two- or three-point contact, indicating how many points on the gauge head touch the inside of the bore. Two-point contacts are better at measuring ovality, while three-point contacts are used to measure lobing or triangular form error. Pistol-grip bore gauges are used for fast, single-handed operation with repeatable results from one operator to another. Bore gauges can also be used in special applications, such as measuring threads, spline pitch diameters, and deep bores.
The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company, founded in 1880, is headquartered in Athol, MA.