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DRILL TERMS:

 

AXIS: The imaginary straight line which forms the longitudinal center line of the drill.
BACK TAPER: A slight decrease in diameter from the front to the back in the body of a drill.
BODY: The portion of the drill extending from the shank or neck to the outer corners of the cutting lips.
BODY DIAMETER CLEARANCE: That portion of the land that has been cut away so it will not rub against the walls of the hole.
BUILT-UP-EDGE: An adhering deposit of nascent material on the cutting lip of the point of the drill.
CAM RELIEF: The relief from the cutting edge to the back of the land, produced by a cam actuated cutting tool or grinding wheel on a relieving machine.
CHIPBREAKER: Nicks or grooves designed to reduce the size of the chips. They may be steps or grooves in the cutting lip or in the leading face of the land at or adjacent to the cutting lips.
CHIP PACKING: The failure of chips to pass through the flute during the cutting action, generally resulting in tool failure.
CHISEL EDGE: The edge at the end of the web that connects the cutting lips.
CHISEL EDGE ANGLE: The angle included between the chisel edge and the cutting lip, as viewed from the end of the drill.
CLEARANCE: The space provided to eliminate undesirable contact between the drill and the work.
CLEARANCE DIAMETER: The diameter over the cut away portion of the drill lands.
CRANKSHAFT OR DEEP HOLE DRILLS: Drills designed for drilling oil holes in crankshafts, connection rods and similar deep holes. They are generally made with heavy webs and higher helix angles than normal.
CUTTER SWEEP: The section formed by the tool used to generate the flute in leaving the flutes.
CUTTING EDGE: See preferred term Lips
DRIFT: A flat tapered bar for forcing a taper shank out of its socket.
DRIFT SLOT: A slot through a socket at the small end of the tapered hole to receive a drift for forcing a taper shank out of the socket.
DRILL DIAMETER: The diameter over the margins of the drilled measured at the point.
EXPOSED LENGTH: The distance the large end of a shank projects from the drive socket or large end of the taper ring gage.
EXTERNAL CENTER: The conical point on the shank end of the drill, and the point end on some sizes of core drills.
FLAT DRILL: A drill whose flutes are produced by two parallel or tapered flats.
FLAT (SPADE) DRILL: a removable cutting drill tip usually attached to a special holder designed for this purpose. Generally used for drilling or enlarging cored holes.
FLUTE LENGTH: The length from the outer corners of the cutting lips to the extreme back end of the flutes. It includes the sweep of the tool used to generate the flutes and, therefore, does not indicate the usable length of flutes.
GALLING: An adhering deposit of nascent work material on the margin adjacent to the leading edge at and near the point of the drill.
GUIDE: A cylindrical portion, following the cutting portion of the flutes, acting as a guide to keep the drill in proper alignment. The guide portion may be fluted, grooved or solid.
GUN DRILL: Special purpose straight flute drills with one or more flutes used for deep hole drilling. They are usually provided with coolant passages through the body. They may be either solid or tipped.
HALF-ROUND DRILL: A drill with a transverse cross-section of approximately half a circle and having one cutting edge.
HELICAL FLUTES: Flutes which are formed in a helical path around the axis.
LAND: The peripheral portion of the body between adjacent flutes.
LAND CLEARANCE: See preferred term Body Diameter Clearance.
LAND WIDTH: The distance between the leading edge and the heel of the land measured at a right angle to the leading edge.
LEAD: The axial advance of a leading edge of the land in one turn around the circumference.
LEAD OF FLUTE: See preferred term Lead.
LENGTH OF TWIST: See preferred term Flute Length.
LIPS: The cutting edges of two flute drills extending from the chisel edge to the periphery. On Core Drills, the cutting edges extending from the bottom of the chamfer to the periphery.
LIP RELIEF: The axial relief on the drill point.
LIP RELIEF ANGLE: The axial relief angle at the outer corner of the lip. It is measured by projection into a plane tangent to the periphery at the outer corner of the lip.
MARGIN: The cylindrical portion of the land which is not cut away to provide clearance.
MULTIPLE-MARGIN DRILL: A drill whose body diameter clearance is produced to leave more than one margin on each land.
NECK: The section of reduced diameter between the body and the shank of a drill.
NOTCHES: See preferred term Chip Breaker.
OIL GROOVES: Longitudinal straight or helical grooves in the shank, or grooves in the lands of a drill to carry cutting fluid to the cutting edge.
OIL HOLES OR TUBES: Holes through the lands or web of a drill for passage of cutting fluid to the cutting edge.
OVERALL LENGTH: the length from the extreme end of the shank to the outer corners of the cutting lips. It does not include the conical shank end often used on straight drills, nor does it include the conical cutting point used on both straight and taper shank drills. Core Drills; For drills with an external center on the cutting end, it is the same as for two flute drills. For those with internal centers on the cutting end, the overall length is from the extreme ends of the tool.
PERIPHERY: The outside circumference of a drill.
PERIPHERAL RAKE ANGLE: The angle between the leading edge of the land and an axial plane at the drill point.
PILOT: A cylindrical portion of the drill body preceding the cutting lips. It may be solid, grooved or fluted.
POINT: The cutting end of a drill, made up of the ends of the lands and the web. In form it resembles a cone, but departs from a true cone to furnish clearance behind the cutting lips.
POINT ANGLE: The angle included between the cutting lips projected upon a plane parallel to the drill axis and parallel to the two cutting lips.
RAKE ANGLE: See preferred term Peripheral Rake Angle.
RELIEF: The results of the removal of tool material behind or adjacent to the cutting lip and leading edge of the land to provide clearance and prevent rubbing (heel drag).
SHANK: The part of the drill by which it is held and driven.
SLEEVE: A tapered shell designed to fit into a specified socket and to receive a taper shank smaller than the socket.
SOCKET: The tapered hole in a spindle, adapter or sleeve, designed to receive, hold, and drive a tapered shank.
SPIRAL ANGLE: See preferred term Helix Angle.
SPIRAL FLUTES: See preferred term Helical Flutes.
STEP DRILL: A multiple diameter drill with one set of drill lands which are ground to different diameters.
STRAIGHT FLUTES: Flutes which form lands lying in an axial plane.
SUBLAND DRILL: A type of multiple diameter drill which has independent set of lands in the same body section for each diameter.
TANG: The flattened end of a taper shank, intended to fit into a driving slot in a socket.
TANG DRIVE: Two opposite parallel driving flats on the extreme end of a straight shank.
TAPER DRILL: A drill with part or all of its cutting flute length ground with a specific taper to produce tapered holes. They can be for either drilling the original hole or enlarging an existing hole.
WEB: The central portion of the body that joins the lands. The extreme end of the web forms the chisel edge on a two-flute drill.
WEB THICKNESS: The thickness of the web at the point. unless other specific location is indicated.
WEB THINNING: The operation of reducing the web thickness at the point to reduce drilling thrust.

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Last modified: October 02, 2001