Multi-function power shear machines

A convertible sheet metal and plate power shear machine, comprising:

• a machine-surfaced table base (2) having a rear side and parallel side, edges, upstanding side members attached to each of said parallel side edges and a top cross beam (4) secured between said upstanding two side members (3);
• a shear having a bottom blade (5) bolted to said rear and side of said machine-surfaced table base (2) cooperating with a top blade (6) capable of vertical sliding displacements by sliding through a first pair of vertical grooves provided on facing portions of said side members (3);
• a hold-down (10) capable of vertical displacements in front of said top blade (6) and overlaying said table base (2) through a second pair of vertical grooves on said facing portions of said side members (3);
• and
• means (7', 7", 11', 11") for controlling said top blade (6) and said hold-down (10) to slide up and down independently of each other,
• wherein said hold-down (10) includes two separable top and bottom parts (10a, 10b) each supporting, on a face thereof, at least one cooperating tool (14a, 14b) for performing forming and machining operations and a means for temporarily locking together said separate parts (10a, 10b) of said hold-down (10), and for allowing said hold-down (10) to apply a hold-down force on a part to be sheared by said shear.