Worn inserts tell you exactly what went wrong. Reading the pattern fixes the root cause.
1. Flank Wear (most common)
Look for: Smooth wear band on the relief face of the insert, parallel to cutting edge.
Cause: Normal abrasion from cutting. Acceptable up to VB = 0.3mm typical.
Fix: Index when VB reaches 0.3mm. If wearing too fast: harder grade or lower speed.
2. Crater Wear
Look for: Concave depression on the rake face (top of insert, where chip flows).
Cause: High temperature + chemical reaction (diffusion wear). Common in steel at high speed.
Fix: Use grade with Al2O3 outer coating (CVD). Or reduce speed 15-20%.
3. Built-Up Edge (BUE)
Look for: Material smear on cutting edge, often grayish.
Cause: Cutting in BUE temperature window (200-400°C aluminum, 600-800°C stainless).
Fix: Increase speed 30-50% to push past BUE temp. Use polished or coated insert. See BUE guide.
4. Notch Wear (depth-of-cut line)
Look for: Deep groove at depth of cut line (where cutting edge meets uncut surface).
Cause: Work-hardened skin (from previous pass), oxidation, or scale.
Fix: Vary depth of cut between passes (don’t always cut at same depth). Use tougher grade. Reduce Vc.
5. Edge Chipping
Look for: Small chips along edge (different from one big break).
Cause: Interrupted cuts, vibration, hard inclusions, or wrong edge prep.
Fix: Use honed or T-land edge prep. Reduce overhang. Tougher grade. See 8 causes of chipping.
6. Plastic Deformation
Look for: Cutting edge bent or pushed back.
Cause: Excessive temperature exceeding carbide softening point.
Fix: Lower speed dramatically, use harder grade, improve coolant.
7. Thermal Cracks (perpendicular to cutting edge)
Look for: Small cracks running 90° to cutting edge.
Cause: Thermal cycling — coolant intermittently reaching cut.
Fix: Run consistently flooded OR completely dry. Avoid intermittent coolant.
8. Mechanical Cracks (parallel to cutting edge)
Look for: Cracks running parallel to cutting edge, often in interrupted cuts.
Cause: Impact load too high for grade.
Fix: Tougher grade (higher number), stronger edge prep (T-land), reduce feed.
Inspection Practice
- Use 10-20× loupe for routine inspection
- Use shop microscope (50-100×) for diagnostic sessions
- Photograph wear patterns when problems arise (helps suppliers diagnose)
- Track wear by tool number and parameters
For grade selection by application, browse our insert catalog.
Shop Related Products at HOOGUU
