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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.
CLICK HERE FOR GLOSSARY OF
METALWORKING TERMS
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