heat treatable steels, carbon steel, and structural steels.
▪Stainless and acid-proof steel, high heat-resistant alloys based on nickel and cobalt content.
▪Cast iron, grey cast iron, malleable cast iron, and chilled iron.
2.Insert Geometry
The shape of the insert selected must suit the type of machining operation to be performed (roughing or finishing), the contour of the form to be machined, the shape and hardness of the part, and the surface finish required. The following are some general guidelines to follow when selecting the shape of the insert.
▪Square inserts have the strongest structural shape (90° point angle). They are used where a lead angle is desirable and for chamfering tools.
▪Triangular inserts have a 60° point angle that allows producing square shoulders, cutting contour forms, chamfering, and plunge cutting.
▪Round inserts provide shallow feed marks at high speeds on finishing passes. They are excellent for roughing cuts, especially on cast iron.
▪Rectangular inserts are used for heavy-duty machining.
▪Diamond inserts with an 80° point angle are used as combination turning and facing tools; 55° nose angle inserts are used for machining contour forms.
▪Threading and grooving inserts are available for specific thread forms and tool widths.
MANUFACTURER CODING SYSTEMS
The cutting tool insert suppliers have reduced the number of carbide grades and chip groove geometries necessary for good performance. Furthermore, the easy-to-use, color code systems enable users to select exactly the right insert for the job. Special machining requirements that fall outside of the color-coded systems are addressed with specific and customized recommendations on a case-by-case basis. The carbide insert selection systems developed by the four leading carbide tool manufacturers are explained as a guide to assist in the selections of carbide insert tools.
CARBOLOGY’S SECOLOR 3 X 3 MATRIX SYSTEM
Secolor is a system that simplifies the selection of the correct inserts for most machining operations. It is based on color coding in accordance with the ISO standard for the application of cemented carbides. The blue color is for steels, yellow is for stainless steels, and red is for cast iron.
Each color has a different shade for finishing (F), medium-rough machining (M), and rough machining (R), Fig. 3-2-6.
Carbide Grades:
▪TP100 is used for high-speed machining in steel and is the first choice for cast iron.
▪TP200 is the first choice for medium-to-rough turning of steel and is a good choice cast iron, excellent for stainless steel.
▪TP300 provides the toughness and reliability needed for general turning of steel and stainless steel and is first choice for severe interrupted turning conditions of steel.
Carboloy’s three first-choice chip breakers are:
1.MF2 is designed for finishing cuts and has a modified groove that can control chips at depths of cut as low as .010 in., Fig. 3-2-6.
2.M3 is the most versatile chip breaker and is adapted for near-net shape forging and castings.
3.MR7 is designed for more demanding operations at high feed rates, interrupted cuts, and other combinations when edge strength is needed.
This selection method does not apply to turning very difficult-to-machine materials, such as titanium, nickel, cobalt or iron-based high temperature alloys. Carboloy has selection charts for polycrystalline cubic boron nitride (PCBN) inserts used for turning hardened alloy steels and cast iron.
KENNAMETAL GRADE SYSTEM
The Kennametal grade system consists of four basic groups of workpiece materials, Fig. 3-2-7. Each group contains a variety of insert grades to suit various metalcutting conditions.
▪Tungsten carbide: This group consists of uncoated, chemical vapor deposition (CVD) coated and physical vapor deposition (PVD) coated inserts. Each coated grade consists of various substrates of unalloyed (straight WC/Co) and alloyed (WC/TaC/NbC/Co) compositions.
Fig. 3-2-6 The coding system for three carbide grades and chipbreakers that cover a wide working range. (Carboloy, Inc.)
▪Cermet: Cermets consist mostly of titanium carbide (TiC) and titanium nitride (TiN) with a metallic binder.
▪Ceramic: The ceramic cutting tools can be divided into two basic families; alumina-base (aluminum oxide) ceramics, and silicon nitride-base (sialon) ceramics.
▪Polycrystalline: These inserts are divided into two basic families; polycrystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN).
The six basic workpiece material groups are:
1.Steel, ferritic and martensitic stainless steels.
2.Hardened steels and hardened irons.
3.Austenitic stainless steels, free-machining and low carbon steels.
4.Cast irons
5.Nonferrous material.
6.Heat-resistant alloys and titanium.
Fig. 3-2-7 The insert tooling grade system. (Kelmar Associates)
Selection Procedures:
The steps in selecting the correct insert from the Kennametal color-coded system are to choose the insert geometry, grade, and cutting speed for the type of material being cut and the machining operation. It is always wise to use the manufacturer’s selection guide when selecting inserts. Table 3-2-4 lists the suggested grades and machining conditions for free-machining and low carbon steels.
SANDVIK’S CoroKey
The CoroKey system developed by Sandvik, Inc., converts the selection of inserts into turning, milling and drilling applications. The ISO standard divides workpiece materials into three major areas with appropriate color coding:
▪ISO P (Blue) is designed for long chipping materials including steels, steel castings, and martensitic/ferritic stainless steels, Fig. 3-2-8.
▪ISO M (Yellow) covers austenitic stainless steels, superalloys, and titanium, Fig. 3-2-9.
▪ISO K (Re) is designed for short-chipping materials including cast iron, hardened materials
