Application of Coolant-Chip-Ejector Drilling.

A program was conducted to evaluate the Sandvik coolant-chip-ejector drilling system for manufacturing purposes at Rock Island Arsenal. The Sandvik Ejector Drill, which has an insert-type head with unique cutting geometries, produces small chips which are swept back through a center tube of its annular tool shank by the coolant. A series of tests were performed on two materials, namely, AISI 4140, a low-alloy steel, and CG 27, an iron base super alloy. The two materials presented considerably different machining characteristics, thereby providing a basis to determine the usefulness of the Sandvik drilling system. Drilling of deep holes at speeds comparable to those of gun drills and feeds comparable to those of twist drills was possible with accuracies and surface finishes equivalent to those obtainable by reaming. Surface hardening of the work material was lower than that caused by gun drilling and bore reaming, especially when drilling the CG 27 alloy. Consequently, multistep operations of machining, straightening and stress relieving were eliminated in many instances. Machining rates up to ten times faster than twist drilling and up to twenty times faster than gun drilling were realized.