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General turning

Troubleshooting in turning

Cause Solution

Chip control
Long, unbroken snarls winding around the tool or workpieces. Caused normally by low feed, low and/or shallow depth of cut.​

​ ​
  • 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.​​
  • 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.
  • 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.
  • 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.

  • Unsuitable entering angle
  • Select a larger entering angle (lead angle). KAPR = 90°
    (PSIR = 0°)
  • Nose radius is too large
  • Select a smaller nose radius
  • Unsuitable edge rounding, or negative chamfer
  • Select a grade with a thin coating, or an uncoated grade​
  • Excessive flank wear on the cutting edge​
  • Select a more wear resistant grade or reduce speed

Vibration
High tangential cutting forces.

  • Insert geometry creating high cutting forces
  • Chip breaking is too hard, producing high cutting forces​
  • Select a positive insert geometry
     
  • Reduce the feed or select a geometry for higher feeds​
  • Cutting forces vary or are too low due to small depth of cut
  • Increase the depth of cut to make the insert cut
  • Tool is incorrectly positioned​
  • Check the centre height​
  • Instability in the tool due to long overhang
  • Reduce the overhang
  • Use the largest possible bar diameter
  • Use a Silent Tools™ or a carbide bar
  • Unstable clamping leads to insufficient rigidity
  • Extend the clamping length of the boring bar
  • Use EasyFix™ for cylindrical bars
 

Insert wear

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.

CauseSolution​

​​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
 
 

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