Twist Drill Tool Nomenclature for Drilling, Drill bit Geometry | Manufacturing Processes | Ifinfotech

In todays session will learn about twist drill nomenclature. here Twist drills are rotary cutting tools that normally have two cutting edges and two flutes which are grooves formed in body to provide cutting lips, to permit removal of chips and to allow coolant or cutting fluid to reach the cutting action. They are identified by the Shank style. here the Figure shows A schematic of design features for twist drills. and The following terms used to design twist drill so here first is Drill Axis which is imaginary straight line which forms longitudinal center line of drill. here Drill diameter is the diameter over the margins of drill measured at periphery corners. here Flutes are Helical or straight grooves formed in body of drill to provide cutting lips, to permit removal of chips, and to allow cutting fluid to reach the cutting lips. here land is the peripheral portion of cutting tooth and drill body between adjacent flutes. Helix angle is the angle made by leading edge of land with plane containing axis of drill. (Helix angle = 30° or 45°) here Body is a part of drill from its extreme point to commencement of neck. here Shank is a part of drill by which it is held and driven. The shank may be straight or taper. here Flank is the Surface of drill which extends behind the lip to flute. here Margins is the cylindrical portion of land that is not cut away to provide clearance. Point angle is the angle included between two lips projected upon a plane parallel to drill axis and parallel to the two cutting lips. (Point angle = 118°) Chisel Edge is the point where two cutting lips meets at extreme tip. Chisel Edge Angle is the angle included between chisel edge and cutting lip, as viewed from end of drill. here Lip is the cutting edge formed at the intersection of flank and flute. here Face is the flute surface portion adjacent to lip. here web is the central portion of drill situated between roots of flutes and extending from point toward shank. here the pointed end to web forms the chisel edge.