The Starrett 18AA automatic center punch with adjustable stroke is 4" long with a 7/16" (11 mm) diameter for creating a starter dimple without the need for a hammer. The punch has an adjustable stroke, which can be set by turning the knurled cap and is regulated by spring tension for uniform dimple size at every setting. The punch is made from hardened and tempered steel components that provide wear resistance and strength. It has a round handle that is knurled for grip. The point can be removed for replacement or sharpening.

Center punches make small dimple marks in a workpiece to help guide a drill bit. Manual center punches have a metal shank with a point and are typically tapped with a ball-peen hammer to mark the material. Automatic center punches have an internal spring mechanism that enables them to mark the material without using a hammer, leaving one hand free for steadying the work.

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.