There is a distinction in cutting edge geometry between negative and positive insertgeometry:
- A negative insert has a wedge angle of 90" seen in a cross-section of the basic shapeof the cutting edge.
- A positive insert has an wedge angle of less than 90°.
The negative insert has to be inclined negatively in the tool holder so as to provide aclearance angle tangential to the workpiece while the positive insert has this clearancebuilt in.
Negative style
- Double/single sided
- Edge strength
- Zero clearance
- External/internal machining
- Heavy cutting conditions.
Positive style
- Single sided
- Low cutting forces
- Side clearance
- Internal/external machining
- Slender shafts,small bores.
*Note: The clearanceangle is the anglebetween the frontface of the insert andthe vertical axis of theworkpiece.
Metal cutting is very much the science of removing chips from the workpiece material inthe right way. Chips have to be shaped and broken off into lengths that are manageablein the machine.
- In milling and drilling a lot of parameters influence thechip formation compared to turning.
- Turning is a single-cut operation with a stationary too!and a rotating workpiece.
- The insert rake angle, geometry and feed play animportant role in the chip formation process.
- Removing heat from the cutting zone through the chip (80%) is a key issue.
