Tumbler gear mechanism is used to change the direction of lead screw and feed rod in lathe machines. By Engaging tumbler gear, the carriage can be moved automatically from tailstock end to headstock
Gap or extension-type lathes are similar to toolroom lathes except that gap lathes can be adjusted to machine larger diameter and longer workplaces The operator can increase the swing by moving the bed a distance from the headstock, which is usually one or two feet.
In a gap bed lathe, the gap is provided just below the nose of the headstock spindle.
Ball centre is sometimes used for tapering by the "set-over tail stock" method. The standard centres cannot sit squarely in the center hole when the tail stock is set over.
Swivelling the compound rest method is used for cutting steep taper.
Mandrel is used to hold the work-piece for machining diameter concentric to its hole or bore.