Abstract: A rigid tool slide support is disposed to be mounted in a screw machine in either of two different operating positions in each of which a tool slide reciprocates on the upper surface of the support to convey a cutting tool to and from the work that is to be machined. Projecting centrally from the bottom surface of the slide is an elongate, dovetail shaped guide which is slidably mounted in a similarly shaped but slightly wider recess in the support. Secured in the recess of the support adjacent one side thereof, and slidably engaged with a confronting side of the dovetail guide of the slide, is an elongate expansion gib having therein an adjusting screw that is rotatably adjustable to expand or contract the length of the gib, thereby to adjust the running clearance between the support and the slide.