Boring head centering apparatus

A boring head centering apparatus for centering a boring head within a cylinder which comprises a cylindrical boring head carrier having a central bore, a cylindrical boring head connected to said carrier and having a rotary axis on the rotary axis of said boring head carrier, said boring head having a first cavity, a centering pinion mounted within the bore of said carrier and extending into said first cylindrical cavity, said centering pinion having gearing at an end of said centering pinion positioned in said first cavity, said boring head having a second cavity opening into said first cavity and a third cavity opening into said second cavity, an idler pinion mounted within said second cavity and in operative contact with the gears of said centering pinion, a boring head pinion mounted in said third cavity in operative contact with said idler pinion and extending beyond said boring head, said boring head pinion having means for securing the boring head pinion within said third cavity, a centering gear mounted on said boring head and having a rotary axis along the axis of said boring head and carrier axis and in operative connection with said boring head pinion, at least three centering fingers mounted at equal distances about the periphery of said boring head, each of said fingers having gear teeth on a first end in operative contact with said centering gear, finger pins mounted in said boring head, said fingers mounted on said finger pins at said first end, a boring head plate connected to said boring head to capture the fingers between the plate and the boring head and means to rotate said centering pinion and transmit rotary motion through said centering pinion, idler pinion, boring head pinion, and centering gear to said fingers to move the fingers outwardly in an arc from said boring head and into contact with the walls of said cylinder.