Indexable cutting tool system

A system for excavating and/or trenching hard and soft ground material includes a support block having a bore with a cylindrical portion and a non-cylindrical portion with flat surfaces and a cutting tool mounted in the bore, which may be a non-rotatable cutting tool having a shank with flat surfaces or a rotatable cutting tool having a shank with a cylindrical portion. The non-cylindrical portion of the bore rotatably engages the cylindrical portion of the rotatable cutting tool and the flat surfaces of the bore engage the flat surfaces of the non-rotatable cutting tool. A further embodiment includes a support block having a bore with flat surfaces along the entire length of the bore that engage the flat surfaces of the shank of the non-rotatable cutting tool and which bore receives the cylindrical portion of the shank of the rotatable cutting tool but does not restrain rotation thereof. In yet another embodiment, the support block may have two non-cylindrical portions and a single cylindrical portion, while the cutting tool may have a shank with two non-cylindrical portions and a single cylindrical portion corresponding to those within the bore of the support block.