A horizontal boring machine or horizontal boring mill is a machine tool which bores holes in a horizontal direction. There are three main types — table, planer and floor. The table type is the most common and, as it is the most versatile, it is also known as the universal type. A horizontal boring machine has its work spindle parallel to the ground and work table. Typically there are 3 linear axes in which the tool head and part move. Convention dictates that the main axis that drives the part towards the work spindle is the Z axis, with a cross-traversing X axis and a vertically-traversing Y axis. The work spindle is referred to as the C axis and, if a rotary table is incorporated, its center line is the B axis.