Glossary of Terms
DRILL – A rotary end cutting tool having one or more cutting lips and having one or more helical or straight flutes for the passage of chips and the admission of a cutting fluid.
AXIS – The imaginary straight line which forms the longitudinal center line of the drill.
BACK TAPER – A slight decrease in diameter from point to back in the body of the 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.
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 DIAMETER – The diameter over the cut away portion of the drill lands.
FLUTES – Helical or straight grooves cut or 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.
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 the flutes.
HELIX ANGLE – The angle made by the leading edge of the land with a plane containing the axis of the drill.
LAND – The peripheral portion of the body between adjacent flutes.
LAND WIDTH – The distance in a transverse plane between the leading edge and the heel of the land measured at a right angle to the leading edge.
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.
NECK – The section of reduced diameter between the body and the shank of a drill.
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 shank drills, nor does it include the conical cutting point used on both straight and taper shank drills.
PERIPHERAL RAKE ANGLE – The angle between the leading edge of the land and an axial plane at the drill point.
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 lips projected upon a plane parallel to the drill axis and parallel to the cutting lips.
SHANK – The part of the drill by which it is held and driven.
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.
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 another specific location is indicated.
WEB THINNING – The operation of reducing the web thickness at the point to reduce drilling thrust.
Types of Drill Bits
Tungsten Carbide Tipped Hole Cutters
Cobalt Reduced Shank Drills – Silver and Deming, and High Split Pointed Steel
Drill Bit Sets – Carbide Tipped, Jobber Blitz Bits, Metric Jobber. Reduced Shank and Solid Carbide Sets.
Extra Length Aircraft Extension Drills – Because of the inaccessibility or the extreme depth of a hole it is found that even long series drills are not long enough. The drilling of such holes generally requires the use of an Extra Length Drill. Popular Item!!!
Hex Head Construction Reamers – Manufactured from a premium grade of m-7N molybdenum high speed steel. The Nitro Heavy-Duty Construction Reamers have a Ferritic Nitro Carbonizing surface treatment which gives a hard protective layer to the reamer.
Nitro High Speed Spiral Reamers – High Speed Spiral 1/2″ Shank Nitro Construction Reamers
Taper Shank Adapters
Taper Shank Drill Bits – High Speed Steel, Black Oxide
Diamond coated 2 mm bits, used for drilling materials such as glass.
Black oxide is an inexpensive black coating. A black oxide coating provides heat resistance and lubricity, as well as corrosion resistance. Coating increases the life of high-speed steel bits.
Titanium nitride (TiN) is a very hard ceramic material that can be used to coat a high-speed steel bit (usually a twist bit), extending the cutting life by three or more times. However, when the bit is sharpened the new edge will not have the benefits of the coating.
Titanium aluminum nitride (TiAlN) is a similar coating that can extend tool life five or more times.
Titanium carbon nitride (TiCN) is another coating also superior to TiN.
Diamond powder is used as an abrasive, most often for cutting tile, stone, and other very hard materials. Large amounts of heat are generated by friction, and diamond coated bits often have to be water cooled to prevent damage to the bit or the work piece.