Abstract: A machine tool for scribing arcs and circles on work pieces comprising an elongated arm having a vertical stud adjacent one end for mounting in a chuck on a rotary spindle, a slide having a plurality of scribing styluses of different sizes disposed at an angle to each other and extending perpendicularly from the outer surface, the slide being movable along the arm to dispose the styluses selectively at desired precise distances from the stud and the slide also being rotatable on the arm to position one of the styluses in parallelism with the stud, a clamping thumb screw threaded into the slide for engagement with the arm to releasably secure the slide to arm at a selected position thereon, slide having a notch extending into the face nearest stud and adapted to receive the same when very small radii are desired, and a fixed reference flange on the stud end of arm positioned outwardly from the axis of stud a distance equal to the distance between the axis of the stylus on slide and the face of the slide neares