7/8" X 5/16" Pilots for Counterbore DEWPIL7/8X5/16

Size: 7/8, Material: High Speed Steel, Finish: Uncoated (Bright), Overall Length: 2-1/8, Shank Size: 5/16, Shank Type: Round Counterboring is the enlargement of a portion of a hole that has previously been formed. If the counterbored portion is shallow (1/8" or less), the operations is usually known as spot-facing; for example, a flat seat for a bolt head or nut. If, on the other hand, the hole is enlarged to a considerable depth, it is designated as counterboring. These counterbores are made of two-piece construction, having an integral shank and counterbore-cutter, and a pilot that is interchangable, which provides flexibility in the use of the tool.