11-08-2012, 02:45 PM
Basics of Cutting Tool Geometry
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For many years there were different systems used to define a great variety of
angles of faces and edges of cutting tools. Although ISO Standard ISO 3002.1977
“Geometry of the Active Part of Cutting Tools - General Terms, Reference Systems,
Tool and Working Angles” has partially resolved this situation by definition of a system
of planes and a number of angles, a number of deficiencies in definition of certain
angles have been noted. The many angles defined by the standard are not necessarily
independent, and many trigonometric relations describing the various angles are
different from those usually developed for an acute angle of orientation of the cutting
edge.
The following systems for identifying cutting tool geometry were introduced in [1]:
1. Tool-in-Hand System: Definitions of the basic reference planes (the main
reference plane; the assumed working plane; the tool cutting edge plane; the tool
back plane; the orthogonal plane; the cutting edge normal plane) for each of the
cutting edges. A system of tool angles (the tool cutting edge angle; the tool
minor (end) cutting edge angle; the tool approach angle; the rake angles; the
clearance (flank) angles; the wedge angles; the cutting edge inclination angle),
their definitions, meaning, and interrelationships among them.
2. Tool-in-Machine System (Setting System) of Angles and Planes.
3. Tool-in-Use System.
The following is to provide the definitions of some basic plane and angles in the
Tool-in-Hand system.
Planes
The working part of the cutting tool basically consists of two surfaces intersecting
to form the cutting edge. The surface along which the chip flows is known as the rake
face or more simply as the face, and that surface which is ground back to clear the new
or machined surface is known as the flank surface or simply as the flank. In the
simplest yet common case the rake and flank surfaces are planes.
Figure 1 shows the definition of the main reference plane Pr as perpendicular to
the assumed direction of primary motion and the tool-in-hand coordinate system. In this
figure, vf is the assumed direction of the cutting feed. Because angles of the cutting tool
are defined in a series of reference planes, the standard defines a system of these
planes in the tool-in-hand system, as shown in figure 2. The system consists of five
basic planes defined relative to the reference plane Pr. Perpendicular to the reference
plane Pr and containing the assumed direction of feed motion is the assumed working
plane Pf. The tool cutting edge plane Ps is perpendicular to Pr , and contains the side
(main) cutting edge (1-2 in Fig. 1). The tool back plane Pp is perpendicular to Pr and Pf.
Perpendicular to the projection of the cutting edge into the reference plane is the
orthogonal plane Po. The cutting edge normal plane Pn is perpendicular to the cutting
edge.
The Application Of Vector Analysis To The Study Of Cutting Tool Geometry
As a first step in the application of vector analysis to cutting tool geometry
problems, consider the determination of the cutting edge inclination angle in the tool-inmachine
system. Figures 5 shows a single-point tool having a zero inclination angle
(λs = 0) in the tool-in-hand system (i.e., its side cutting edge1-2 is horizontal). In tool-inmachine
system, the tool in installed so that its tip 1 is shifted relative to the reference
plane on distance h. The problem is to determine the resultant cutting edge inclination
angle due to this shift.