In a tool change system for a vertical lathe or the like, a new and improved arrangement for clamping a tool block in a tool supporting ram. The new clamping means provides a firm support for the tool block and further includes means for equalizing the clamping forces applied to the tool block and for properly positioning and orienting the tool block in the ram. In accordance with a specific feature of the present invention, the tool block is provided with clamp engaging means on opposite sides thereof and the clamping means comprises a pair of spaced clamping bars engageable with the respective clamping means on the tool block. A common actuating means is operative to move the clamping bars into a tight clamping relation with the clamping means of the tool block. Means are provided for effectively distributing the clamping force applied by the actuating means which comprise a first connecting means for yieldably interconnecting the actuating means to one of the clamping bars and a second connecting means for non-yieldably interconnecting the actuating means to the other of the clamping bars. The non-yieldable second connecting means is arranged on the side of the tool block from which the work approaches.