Abstract: A steady rest for centering a rotationally symmetrical workpiece in a space, the rest comprising two housing halves arranged at a distance from one another and connected together, a plate-shaped middle piece disposed between the two housing halves, the middle piece being mounted in the housing halves by means of an actuator piston which can be moved in an axial direction to the workpiece, two linear guide grooves disposed in both opposite large-surface end faces of the middle piece, with the guide grooves running in a cross-shaped arrangement and at an angle to a movement direction of the middle piece, two outer steady rest arms, each mounted in one of the linear guide grooves of the middle piece in a movable arrangement, and a middle steady rest arm attached to the middle piece between the outer steady rest arms.