Drill bits terminology

Axis The imaginary straight line which forms the lengthwise center of a drill.

Body The section of a drill from the shank to the outer edges of the cutting lips.

Body Clearance Diameter The portion of the land that has been cut away so it will not bind against the walls of the hole.

Chip Removal The ability of a drill to pull material that has been cut away from the point,up the flutes and out of the hole.

Chisel Edge The edge at the end of the web that connects the cutting lips.

Chisel-Edge Angle The angle between the chisel edge and cutting lip,as viewed from the end of a drill.

Cobalt Steel A heat-resistant steel that produces increased drill life.

Drill Diameter The diameter over the margins of a drill,measured at the point(Dia.)

Feeds Feed rates for drilling are determined by the drill diameter,machinability of materials and depth of the desired hole.Small drills,harder materials and deeper holes require additional considerations in selecting proper feed rates(IPA).

Flute   Groove cut in the body of drills to provide cutting sur-faces,permit removal of chips and allow cutting fluid to reach cutting surfaces.

Flure length  The distance from the outer edges of the cutting lips to the extreme back of the flutes.

Helix Angle  The angle formed between the leading edge of the land and the axis of a drill.

Nigh-Speed Steel The high quality steel used in drills for most maintenance and industrial applications.

IPM  Feed  Rate in inches Per Minuer=IPR XRPM.

IPR  Inches Per Revolution(Feed).

Land  The  outer portion of the body between two adjacent flutes.Width the distance betweed the leading edge and heel of the land,measured at a right angle to the leading edge.

Lip Relief Angle The relief angle at the outer corner of the lip.

Lip  The cutting edge of a two-flute drill which extends from the chisel edge to the outer edge.

Margin  The narrow raised surface on a drill body along the flute that stabilizes the drill in the hole.

Neck   The section of reduced diameter between the body and the shank of a drill.

Overall Length  The  length from the end of the shank to the outer corners of the cutting lip.

Point  The cone shaped cutting end of a drill,made from the ends of the lands and the web.

Point Angle  The angle of the cutting surfaces on a drill point,commonly118° or 135°.

RPM Revolutions Per Minute=Dia X3.83

SFM Surface Feet Per Minute RPMXDia.X.26

Shank   The part of a drill by which it is held and driven.

Size  Measurement reference for diameter size of a drill,expressed as either Fractional ,Wire ,Letter or Metric.