Feed Screw and Half-Nut

The Feed Screw is a long horizontal driveshaft that allows the Saddle to be driven automatically along the Ways in the X-axis.

The Apron houses the Half-Nut mechanism that allows a split nut to open or close around the rotating Feed Screw. The Feed Screw can be driven either by gears from the Spindle and/or a speed controllable motor. The drive can be as simple as a windscreen wiper motor, with a 12 volt DC controller, or as complex as a box of electronics controlling the Feed Screw via a stepper motor.

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There are various ‘Half Nut’ mechanism designs around. Having studied those found, it is my feeling that the classic ‘cam plate’ that opens and closes half-nut plates in a dovetailed housing, as used in factory-built lathes, is the tried and proven method. The used of CAD drawing allows us to accurately design the cam plate to give the required half-nut movement.