Long, unbroken snarls winding around the tool or workpieces. Caused normally by low feed, low and/or shallow depth of cut.
Cause
Solution
Feed is too low for the chosen geometry
Increase feed
Select an insert geometry with better chip breaking capabilities
Use a tool with precision coolant
Depth of cut is too shallow for the chosen geometry
Increase depth of cut or select a geometry with better chip breaking capability
Too big nose radius
Select a smaller nose radius
Unsuitable entering angle
Select a holder with as large entering angle (lead angle) as possible. KAPR= 90° (PSIR =0°)
Chip control
Very short chips, often sticking together, caused by chip breaking that is too hard. Hard chip breaking often causes reduced tool life or even insert breakages, due to high chip load on the cutting edge.
Cause
Solution
Feed is too high for the chosen geometry
Choose a geometry designed for higher feeds, preferably a single-sided insert
Reduce feed
Unsuitable entering angle
Select a holder with as small entering angle (lead angle) as possible. KAPR= 45°–75° (PSIR 45–15°)
Too small nose radius
Select a larger nose radius
Surface finish
The surface looks and feels “hairy” and does not meet the tolerance requirements.
Cause
Solution
The chips are breaking against the component and marking the finished surface
Select a geometry which guides the chips away from the component
Change entering angle
Reduce depth of cut
Select a positive tool system with a neutral angle of inclination
Hairy surface is caused by excessive notch wear on the cutting edge
Select a grade with better resistance to oxidation wear, for example a cermet grade.
Reduce the cutting speed
Feed is too high, in combination with a nose radius that is too small, a rough surface is generated
Select a wiper insert or a larger nose radius
Reduce feed
Burr formation
Burr formation on the workpiece when entering or exit of the workpiece.
Cause
Solution
The cutting edge is not sharp enough
The feed is too low for the edge roundness
Use insert with sharp edges, PVD coated inserts or ground inserts at small feed rates, < 0.1 mm/rev (0.004 in/rev)
Notch wear at depth of cut, or chipping
Use a holder with a small entering angle
Burr formation at the end or start of cut
End or start the cut with a chamfer or a radius when exiting/entering the workpiece
Vibration
High radial cutting forces due to vibrations or chatter marks which are caused by the tooling or the tool mounting. Typical for internal machining with boring bars.
To achieve optimized cutting data, best possible component quality and tool life, always remember to check the insert/cutting edge after machining. Use this list of causes and solutions to different forms of insert wear as a reference for successful turning.
Cause
Solution
Flank wear Preferable wear type in every application. Offers predictable and stable tool life.
Cutting speed too high
Too tough grade
Insufficient wear resistance
Hard inclusions in workpiece material
Reduce cutting speed
Select a more suitable grade depending on toughness demand or wear resistance
Notch wear
Sticky and/or work-hardening materials
Use a ~90° entering angle (~0° lead angle)
Geometry is too negative
Select a sharper edge
Decrease entering angle
Vary depth of cut
Crater wear
Too high cutting speed and/or feed
Chip breaker too narrow
Chemical dissolution or abrasive wear
Wear resistance too low
Reduce cutting speed or feed
Select a more wear resistant grade
Select a more open/positive geometry
Plastic deformation Depression Impression
High heat load and pressure, cutting temperature too high
Grade too tough/soft
Lack of coolant supply
Reduce heat and pressure load by reducing cutting speed and/or feed
If edge depression, reduce feed first
If flank depression, reduce speed first
Select a more wear/heat resistant grade
Select a more open/positive geometry
Improve coolant supply
Built-up edge (B.U.E)
Too low cutting temperature
Sticky/smeary material
Geometry too negative
Coating too thick
Increase cutting temperature by increasing speed
Select a PVD-coated grade (less BUE on PVD-coatings)
Select a more positive geometry
Flaking
Smeary material
Cutting speed too low
Intermittent machining with coolant
Coating too thick
Increase cutting speed
Turn off coolant
Select a grade with thinner coating and better edge line security (PVD)
Chipping on edge
Unstable conditions
Grade too hard/brittle
Coating too thick (CVD, leading to edge line flaking)
Make the machine conditions more stable
Select a tougher grade
Select a stronger geometry
Select grade with thinner coating (PVD)
Thermal cracks
Varying cutting edge temperatures
Intermittent cuts and coolant
Grade is sensitive to heat shock variations
Use of grade with thicker coating (CVD)
Switch off coolant or apply coolant copiously to obtain an even temperature level
Decrease cutting speed
Select grade with thinner coating (PVD)
Breakage
Excessive wear
Wrong choice of grade (too tough/hard)
Wrong cutting data
Run shorter (time in cut) operations: check how wear begins and the dominant wear type
Change cutting data
Select a more suitable insert grade/geometry
Slice fracture - ceramics
Excessive tool pressure
Reduce feed
Select a tougher grade
Select an insert with a smaller chamfer, or use another geometry to change cutting force direction
Chipping outside cutting zone
Chip jamming because of facing towards shoulder
The chips are deflected against the cutting edge
Not optimized feed or feed direction
Change operation path (to avoid facing towards shoulder)
Change feed
Select a PVD-coated grade
Select an insert geometry that alters the chip flow
