Abstract: The attachment includes a generally U-shaped bracket having a pair of roll arms which are pivotally mounted intermediate their ends on the outer ends, respectively, the two arms of the U-shaped bracket. Each roll arm has a thread roll rotatably mounted on its outer end and a roller follower rotatably mounted on its inner end. The bracket is secured on the slide of a screw machine for reciprocation thereby in a direction selectively to engage the thread rolls tangentially with diametrally opposite sides of a rotating workpiece that is to be threaded.