Member's Area - Machining & Subclass -
Manufacturing Methods - Drilling

No Potential for Subclass Carryover

Drilling – Hole making with a rotary end-cutting tool having one or more cutting lips and one or more helical or straight flutes or tubes for the ejection of chips and the passage of a cutting fluid.

Subclass carryover from the drilling process would not be expected on the work piece.  Tool marks imparted by the tool on the interior of the hole/bore being drilled would appear circular throughout the circumference of the hole/bore.  These tool marks are perpendicular to axis of the bore and, therefore, are perpendicular to the movement of a fired bullet traveling through the barrel’s bore or in the case of a fired cartridge case, being extracted from the chamber producing an individual pattern on the bearing surface of a bullet or on the side of a fired cartridge case.  Tool marks traveling parallel with the axis of the bore do have the potential for subclass carryover.