Abstract: A tool assembly (4) for working a material (R) such as breaking rock. Assembly (4) includes a tool mounting (17) having a fixed section (18), and a movable section (19) for movement relative to the fixed section (18) in a working direction (D.sub.W) and an opposite return direction (D.sub.R). A tool (34) is mounted on the movable section (19) for movement relative thereto in the working direction (D.sub.W) and return direction (D.sub.R). Limit means (49,50) on tool (34) limits relative movement between tool (34) and movable section (19) to between a tool operative position and a tool operated position. During a working stroke, tool (34) is engaged with material (R) and moved in working direction (D.sub.W) from the operative position to the operated position and thereafter in unison with the movable section (19) under action of a working force applied to tool (34) thereby to work material (R).