Speed-reducing box milling-boring clamp

The utility model relates to a boring-milling jig, especially for a speed reducer gearbox, horizontally surmounted by a segmental structure, having an arc curve at an angle of more than 180 degrees and a straight edge. A mounting plate is vertically fixed on the superior surface of the jig and is parallel with the straight edge of the jig. The mounting plate is provided with some fastening screws, on one side of said mounting plate is fixed a locating piece vertical to both of the mounting plate and the jig, the locating piece extends in the direction of front side of the mounting plate, on the jit in correspondance with front side of the mounting plate locating surface is located packing blocks. The utility model is convenient for clamping at one time instead of twice before milling two surfaces of the speed reducer gearbox subtending at each other at an angle of 90 degrees, thereby improving the qualified rate and work efficiency.