Press brake tool holders suitable for releasing and securing press brake tools in response to applied fluid pressure. One press brake tool holder includes a horizontally elongated body having a cam shaft bore disposed longitudinally therethrough, and receiving a slidably and sealingly mounted cam shaft therein. The cam shaft can have at least one axial camming surface, having a large outer diameter region axially tapered to a small outer diameter region, and in contact with a cam follower pin slidably disposed in a cam follower pin bore transversely disposed through the body. The cam follower pin can bear against a pivotally mounted clamp disposed about the body. In response to applied fluid pressure, the camming surface can slide axially, thereby increasing the effective outer diameter as seen by the cam follower pin, thereby urging the cam follower pin outward and against the upper portion of the pivotally mounted clamp, and closing the lower clamp portion about a press brake tool. One press brake tool has a pair of opposed cam shaft segments with the pressure-bearing faces disposed near each other in the center. Another press brake tool holder has a single cam shaft with multiple camming surfaces disposed over the length.