Horizontal boring machine tool

A horizontal boring machine for boring cylindrical surfaces having horizontal axes and axially spaced apart from each other, such as the seats for an engine crankshaft in the crankcase of an internal combustion engine, including:

• a boring bar driven in rotation by a chuck and carrying a pair of diametrically opposed cutting bits, driving means for driving rotation of said chuck, means for axially moving the group composed of the chuck and the associated driving means, a counter-bar coupled in rotation head-to-head with said boring bar and driven in rotation by a respective auxiliary chuck, driving means for driving the rotation of the auxiliary chuck in synchronism with the rotation of the boring bar, means for axially moving the group composed of said counter-bar and the associated driving means, in synchronism with the axial movement of the boring bar, said boring bar being provided with a device for adjusting the radial position of said cutting bits that are associated therewith,
• wherein said counter-bar is also equipped with a pair of diametrically opposed cutting bits, whereby the counter-bar constitutes an auxiliary boring bar, and is provided with means for radial adjustment of the counter-bar cutting bits,
• wherein the pairs of diametrically opposed cutting bits work on the same cylindrical surface each time,
• wherein each cutting bit is carried near the free end of a blade, the opposite end of which is fixed to the body of the associated bar at axially spaced positions and are oriented toward each other with their bit-carrying ends, and which is elastically deformable outwards due to the effect of a radial pin carried by the free end of the blade engaging against a conical portion of a shaft sliding inside an axial cavity of said bar, and
• wherein the axially slideable conical portion causes adjustment of the radial positions of the two diametrically opposed cutting bits on each of said bar and said counter-bar.