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This section is a general overview of basic machining practices. It is intended to familiarize
you with basic setup and operation techniques. Good machining practices extend tool life
and in the end can save money.
Insert Selection
Although inserts are expendable it does not mean that an operator should be careless
in the setup. The following are the most common insert materials used. Each has a
description of its characteristics and common usage.
High Speed Steel
• Allow for higher rake angles
• Resists chipping
• Resists softening due to high temperatures.
Carbide
• Good resistance to high temperatures
• Lower edge strength than high-speed steel
• Different composition of carbide can result in different fi nishes
Ceramic
• Yields good fi nish
• Requires negative rake angle due to low strength
• Requires very rigid setup
• Requires high horsepower
Diamond
• Four times harder than carbide
• Can retain their cutting edge for almost the length of the tool life
• Excellent stability for close tolerance work
• Excellent fi nish quality
NOTE: Remember to use the highest quality tooling designed for CNC
machines to achieve the best cutting condition possible.
Tool Wear
Tool life is dependant upon the following criteria:
• Cutting feedrate
• Tool and workpiece material
• How much material is being removed
• Proper workholding device
• Use of coolants
• Use of correct SFPM (RPM) for tool and material
Tools are subject to gradual wear from the following elements:
Abrasion (Friction and rubbing removes material from the cutter.) Caused by:
• Friction on the outside of the cutter as it passes through the material.
Adhesion High pressure/temperatures weld small chip particles to cutter. Caused by:
• Low cutting speed
• High feed rate
• Negative cutting geometry
• 'Sticky' materials such as some stainless steels and pure aluminum
• Lack of coolants
96-0041 Rev T
January 2009
4 . M ACH I N I N G PRACT I CES
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