Cutting – tool nomenclature.

Cutting – tool nomenclature means systematic naming of the various parts and angles of a cutting tool. The surfaces on the point of a tool bear. Definite relationship to each other that are defined by angles. The principles underlying cutting tool angles are the same whether the tool is a single point tool, a multi point tool, or a grinding wheel. Since a single point tool is the easiest to understand, it will be discussed in greater detail. The basic angles needed on a single point tool may be best understood by removing the unwanted surface from an oblong tool blank of square section. However, the complete nomenclature of the various parts of a single point tool is shown in Figure 1,. these are : shank, face, flank, heel, nose, base, back rake, side rake, side clearance, end cutting edge, wide cutting edge, and lip angle. These elements define the shape of a tool.

The shank is that portion of the tool bit which is not ground to form cutting edges and is rectangular in cross – section.

The face of the cutting tool is that surface against which the chip slides upward.

The flank of a cutting tool is that surface which face the work piece.

The heel of a single point too is the lowest portion of the side cutting edges.

The nose of a tool is the conjunction of the side and end cutting edges. A nose radius increases the tool life and improves surface finish.

The base of a tool is the under slide of the shank.

The rake is the slope of the top away from the cutting edge. The larger the rake angle, the larger the shear angle and subsequently the cutting force and power reduce. A large rake angle is conductive to good surface finish. Each tool has a side and back rake. Back rake indicated that the plane which forms the face or top of a tool has been ground back at an angle sloping from the nose. Side rake indicated that the plane that form the face or top of a tool has been ground back at an angle sloping from the side cutting edge. Side rake is more important than back rake for turning operations.

The side clearance or side relief indicates that the plane that forms the flank or side of a tool has been ground back at an angle sloping down form the side cutting edge. Likewise, the end clearance or end relief indicates that the nose or end of a tool has been ground back at an angle sloping down from the end cutting edge.

The end cutting edge angle indicates that the plane which forms the end of a tool has been ground back at an angle sloping form the nose to the side of the shank, whereas the side cutting edge angle indicates that the plane which forms the flank or side for a tool has been ground back at an angle to the side of the shank. In the main, chips are removed by this cutting edge.

The lip or cutting angle is the included angle is the included angle when the tool has been ground wedged – shaped.

Multi-point tools: Cutters like twist drills, reamers, taps, milling cutters have two or more tool points each. They differ in overall appearance and purposes but each cutting blade acts as and has the basic features of a single point tool. The milling cutter, and drill like a single point tool, have various angles of importance. A milling cutter has clearance, it often has both a secondary and a primary clearance. A land also exists on a milling cutter and a drill. This is the narrow surface resulting from providing a primary clearance. They may have different rakes depending on the intended use.