The type of thread used in lead screw of a lathe is ______

Concept:

• The lead screw is used for thread cutting. It is made from good quality alloy steel and is provided with acme thread or square thread both.
• It is driven from the headstock through the feed gearbox and moves the carriage in a longitudinal direction against the workpiece.

Important Point:

Square thread: 

• In this thread, the flanks are perpendicular to the axis of the thread. This is used for transmitting motion or power. E.g. Fly presses, Screw jack, vice handles, cross-slide, lead screw and compound slide, etc.

Trapezoidal threads: 

• These threads have a profile that is neither square nor V thread form and have a form of a trapezoid. Different forms of trapezoidal threads are ACME thread, Buttress thread, Saw-tooth thread, Worm thread
  • ACME thread: It has an included angle of 29°. 
  • Buttress Thread: In this thread, one flank is perpendicular to the axis of the thread and the other flank is at 45°. These threads are used in the power press, carpentry vices, gun breeches, ratchets, etc.
  • Knuckle thread: The shape of the knuckle thread is not trapezoid, but it has a rounded shape. It has limited applications. It is used for valve spindles, railway carriage coupling, hose connections, etc.