LEAD SCREW

Lead Screws are the most common way to move the X, Y and Z axises on a mill or X and Z axes on a lathe. They turn the rotary motion of the drive motor into linear motion of the axis. There are other methods for producing linear motion such as rack and pinion, linear motor, belt drives and friction drives, but they are the exception.

Lead Screws generally come in two forms

(1) Acme Screw and
(2) Ball Screw (there are some non-acme thread Lead Screws, Lead Screw that uses rollers instead of balls.

Lead Screws are made by rolling through precision dies. The Lead Screw is used for thread cutting. The Lead Screw is driven by the spindle through a gear train. Therefore, the rotation of the Lead Screw bears a direct relation to the rotation of the spindle. When the half-nuts are engaged, the longitudinal movement of the carriage is controlled directly by the spindle rotation. Consequently, the cutting tool is moved a definite distance along the work for each revolution that the spindle makes.

Major features/ Advantages of Lead Screws

•   Smoothness of operation
•   Absolute and repeatable positioning accuracy over a distance
•   Minimum helical no linearity within a revolution (drunkenness). Important for equal step size or constant velocity applications.
•   Anti-backlash nut design for bi-directional repeatability
•   Self-aligning nut eliminates side loading of linear bearings and prevents nut binding or positioning error due to misalignment
     in Lead Screw installation.
•   Self-compensation for pitch diameter variation extends life expectancy without performance degradation.
•   No noise
•   High strength bronze nut for maximum durability
•   One piece nut for maximum stiffness
•   Each screw is lapped with its own nut for maximum contour compatibility
•   Smooth and quiet operation

Lead screws based on the threads are of three types

•   Standard thread
•   Fine pitch thread
•   Inch threads Lead Screws