Subland Drill (2-2)
A Subland Drill (2-2) is basically two drills of different diameters combined into one tool, retaining the individual characteristics and proper geometry for each diameter. The independent flutes and margins of a Subland Drill ensure that size and concentricity between diameters is maintained throughout the life of the tool and is not affected by re-sharpening the point or step angles.
The Subland Drill (2-2) eliminates secondary operations by drilling multi-diameter holes in one production pass. On certain applications particularly holes in steel or cast iron, the Subland Drill (2-2) provides superior tool life compared to that of a basic step drill. When drill bushings are used "Double Margins" can be supplied for greater stability. The additional margins will give maximum support and guidance to provide more accurate size and hole location.
Subland Drills are not practical when the small diameter is less than 50% of the large diameter. Depth of the hole should not exceed 4 times the small diameter, but greater hole depth can be achieved by withdrawing the tool or "pecking" to clear chips.