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Anatomy of a Twist Drill Bits

SHANK — Twist Drill Bit

The shank end of the drill bit is the end by which the bit is held and driven.

Common Shank Types:

3-Flatted Shank - Generally 3 flats designed to allow a strong chuck grip on the shank. Reduces the possibility of the drill slipping in the chuck during tough drill applications.

Reduced Shank - Usually 1/4", 3/8", or 1/2" and are designed to allow a larger diameter drill to be used with a chuck capable of holding only smaller diameter drills.

Tanged Shank - This style of shank is used with a split sleeve drill driver as a replacement for taper shank drills.
Norseman Drill and Tool-Common Shank Types
Shank — The part of a drill by which it is held and driven. Norseman Drill and Tool-Twist Drill Shank
Washout — The extreme increase at the end of the flute, formed by the grinding wheel or cutter. Norseman Drill and Tool-Washout
Web Increase — The web thickness increases in thickness towards the shank to enhance the rigidity of the drill. Norseman Drill and Tool-Web Increase

BODY — Twist Drill Bit

The drill body is that portion of the drill that extends from the shank to outer corners of the cutting lips.

Drill Body — Portion of the drill extending from the end of the flutes to the outer corner of the cutting lips. Norseman Drill and Tool-Twist Drill Body
Drill Axis — Imaginary straight line that forms the center line of the drill.. Norseman Drill and Tool-Axis
Back Taper — Slight decrease in diameter from point towards shank, in the body of the drill. Norseman Drill and Tool-Back Taper
Body Diameter Clearance — The portion of the land that has been cut away so it will not bind against the walls of the hole. Norseman Drill and Tool-Body Diameter Clearance
Neck — The section of reduced diameter between the body and the shank of a drill. Norseman Drill and Tool-Neck
Flute Length — The length from the outer corner of the cutting lips at the point (shoulder) to the extreme back end of the flutes. Example Measurement: 2-11/16" Norseman Drill and Tool-Flute Length
Flute —Grooves formed in the body of the drill to provide cutting lips, to permit removal of chips, and to allow cutting fluid to reach the cutting lips. Norseman Drill and Tool-Flute
Out-of-Round — Not round. If caused from centerless grinding, the part will usually have 3 lobes. Norseman Drill and Tool-Out of Round
Overall Length — The length from the extreme end of the shank to the extreme end of the drill point. Norseman Drill and Tool-Overall Length

POINT — Twist Drill Bit

Drilling today's wide variety of materials efficiently requires a great variety of drill points, types of web thinning and drill design. The proper use of controlled drill pointing and web thinning can result in substantial savings in drilling cost.

Point 118° and Split Point 135° —Split point self centering, requires less thrust in drilling harder metal, breaks up chips. Norseman Drill and Tool-Point 118° and 135° Split point
Point — The cone shaped cutting end of a drill, made from the ends of the land and web. Norseman Drill and Tool-Cone Shaped Point
Cleared Diameter —is measured using a micrometer over the diameter of the cut away portion of the drill lands. Norseman Drill and Tool-Clear Diameter
Cutting Lip — The cutting edge of a two-flute drill which extends from the chisel edge to the outer edge. Norseman Drill and Tool-Cutting Lip
Secondary Cutting Edge — The cutting edge formed by the intersection of the face of the notch with the relieved surface of the point, resulting in partial removal of the chisel edge. Norseman Drill and Tool-Secondary Cutting Edget
Drill Diameter — The diameter over the margins of the drill measured at the point. Norseman Drill and Tool-Drill Diameter
Land — The outer portion of the body between two adjacent flutes. Norseman Drill and Tool-Land
Lip Relief Angle — The relief angle at the outer corner of the lip. Norseman Drill and Tool-Lip Relief Angle
Margin — The narrow portion of the land which is not cut away to provide clearance. It stabilizes the drill in the hole. Norseman Drill and Tool-Margin
Web Thickness — is measured by using a point micrometer positioned at the point end. Norseman Drill and Tool-Web Thickness
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. Norseman Drill and Tool-Web
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