The jig borer is a type of machine tool invented at the end of World War I to make possible the . The jig grinder was developed as a machine with the precision of the jig borer, but . layout (either quickly but imprecisely or painstakingly and precisely) or with drill jigs (themselves made with painstaking and precise layout).
A jig grinder is a machine tool used for grinding complex shapes and holes where the highest degrees of accuracy and finish are required. The jig grinder is very similar to a jig borer, in that the table positioning and spindles are very accurate (far more so than a manual milling machine or lathe).