A cutting tool for boring (40) that is attached to a machining apparatus and used for cutting a hole (13) on a large-diameter side of a stepped hole of a workpiece (10) is provided. The cutting tool for boring (40) is a set of two tools, and each cutting tool for boring (40a, 40b) in the set of two includes a shaft part (41), a cutting blade (42) laterally protruding from the respective shaft parts (41), and an abutment surface (43) formed at the tip of each shaft part (41) and used to cause the tips of the respective shaft parts (41) to butt against each other. Each cutting tool for boring (40a, 40b) performs cutting while the two cutting tools for boring (40a, 40b) rotate integrally around the center line of the shaft parts (41) in a coupled state in which the tips of the cutting tools for boring (40a, 40b) are butted together.

An assembly and method for drilling micro holes in a tube including an outer wall having opposing open ends and forming an inner channel. The method includes the steps of submerging the tube in water so the water fills the inner channel, retaining the water in the inner channel, freezing the water in the inner channel so as to form an ice backing in the inner channel, and drilling through the outer wall such that the ice backing supports the outer wall and prevents the outer wall from deforming or distorting near the hole location.

An assembly and method for drilling micro holes in a tube including an outer wall having opposing open ends and forming an inner channel. The method includes the steps of submerging the tube in water so the water fills the inner channel, retaining the water in the inner channel, freezing the water in the inner channel so as to form an ice backing in the inner channel, and drilling through the outer wall such that the ice backing supports the outer wall and prevents the outer wall from deforming or distorting near the hole location.