Boring tool with a double cutter head, in which the working load is prevented outside the elastic range of the cutting bit holder material in the vicinity of the outermost radial positioning

A cutter head assembly comprising

• a cutter head having a central axis about which said head is rotated during use;
• first and second toothed surfaces on said head facing outwardly away from each other and from said axis, each said toothed surface carrying a linear tooth system in which each tooth lies in a separate plane which is generally perpendicular to said central axis;
• first and second bit holders each having a first portion with a linear tooth system slidably engaging said teeth on one of said outwardly facing surfaces so that each bit holder is radially adjustable to a plurality of positions relative to said central axis for adjusting the cutting diameter of said assembly and so that a portion of said head is between said bit holders;
• on each of said bit holders including a second portion having means for holding a cutting bit and a third, intermediate portion extending through the central axis between and transversely to said first and second portions to form a generally Z-shaped body;
• means for clamping each said bit holder to its associated outwardly facing surface in any one of said plurality of radial positions;
• means on said first portion of each of said bit holders defining a first contact surface on one side of said central axis facing toward the other bit holder;
• and means on said second portion of each bit holder on the other side of said central axis from said first contact surface defining a second contact surface facing said first contact surface on the other bit holder, each said first surface on one bit holder and said second surface on the other bit holder being at least partially overlapping and facing each other over substantially the entire range of radial adjustments of said bit holders.