14- Engine Lathe - Sizing a Lathe
Engine lathes vary in size. Their size is identified by the largest work piece diameter that can be turned without hitting some part of the lathe. This diameter is referred to as the "swing". Size is also determined by the longest part that can fit between centers. So a 13x48 lathe has a 13" swing and can accommodate a 48" long work piece. (figure 1). A typical lathe has a 13 inch swing, 6 foot long bed, and capacity to turn work 36 inches between centers. Small bench engine lathes have a 9 inch or less swing and have a 20 to 35 inch between centers.

Many lathes have a removable section of the ways that provides for turning lager diameters near the head. These are commonly called "gap lathes". There is another unique lathe that is also called a "gap lathe" (figure 2). This lathe can turn larger diameter work than a standard engine lathe of comparable size. The gap lathe has a bed which slides aft (right in the picture), opening a gap near the head. Distance between centers when the bed is fully retracted is 50 percent more than when the bed is in its normal position.