Turning inserts and milling inserts (mainly made of tungsten carbide cemented carbide) can both be reground. Proper regrinding is a practical solution to reduce tool costs and improve resource utilization. For issues such as minor wear, edge dullness, and small-area chip adhesion during machining, professional regrinding can restore their cutting performance, eliminating the need for immediate replacement with new inserts. However, regrinding requires the prerequisites of “no cracks in the insert body, damage within acceptable limits, and sufficient allowance”. Additionally, due to differences in structure and application, turning inserts and milling inserts have distinct regrinding focuses. This article will answer core questions from four dimensions—”whether regrinding is possible”, “prerequisites for regrinding”, “regrinding differences between the two”, and “advantages and precautions”—using plain language and clear tables, helping industry practitioners quickly grasp practical knowledge about regrinding these two types of inserts.
1. Clear Conclusion: Regrinding Is Feasible in Most Cases, with Material and Damage Degree as Core Criteria
Not all turning or milling inserts are suitable for regrinding. The key depends on tool material and damage condition. Tungsten carbide inserts have the highest regrinding value, while coated inserts require a recoating process.
| Tool Material | Suitable for Regrinding? | Recommended Regrinding Times | Core Reason |
|---|---|---|---|
| Tungsten Carbide | Yes (priority for regrinding) | 2-4 times | High hardness and wear resistance; cutting performance after regrinding is close to new inserts |
| High-Speed Steel (HSS) | Yes (limited regrinding) | 1-2 times | Good toughness but lower hardness; precision decreases rapidly after multiple regrindings |
| Coated Carbide | Yes (needs recoating) | 1-3 times | Regrinding removes the surface coating; recoating is required after repair to ensure wear resistance |
| Ceramic/PCD | No | 0 times | Brittle material; regrinding easily causes cracks, with repair costs close to new inserts |
Key Judgment Criteria: Regrinding is only worthwhile when damage is concentrated on the cutting edge (no through cracks or severe chipping). Replace directly if:
- Chipping area exceeds 0.5mm (turning inserts) or 1mm (milling inserts);
- The insert body has cracks or severe edge defects;
- Thickness/diameter reduction exceeds 5% of the original size (insufficient allowance);
- The connection part of the shank/seat is deformed.
2. Prerequisites for Regrinding: Only Worthwhile if These 3 Conditions Are Met
Regrinding of turning and milling inserts must meet the following unified prerequisites; otherwise, post-regrinding precision cannot be guaranteed, and machining quality may be affected:
- Damage type is repairable: Only edge dullness, minor wear (wear ≤0.3mm), small-area chip adhesion or built-up edge, with no large-scale chipping or gaps;
- Insert body structure is intact: No cracks or bending deformation, no severe depressions on the cutting surface, and no collapse or blockage in the flutes (milling inserts);
- Sufficient regrinding allowance: New inserts leave regrinding allowance at the factory (usually ≥0.2mm for carbide inserts). Size reduction after multiple regrindings must not exceed the upper limit to avoid affecting machining tolerances.
Counterexample: If a milling insert has 1.5mm edge chipping due to high-speed collision, or a turning insert has through cracks, even regrinding cannot restore rigidity. Vibration and chipping are likely during machining, potentially damaging workpieces and equipment.
3. Turning Inserts vs. Milling Inserts: Obvious Differences in Regrinding Focus
Due to differences in application and structure, turning inserts and milling inserts have distinct core focuses and requirements during regrinding, as detailed below:
| Comparison Dimension | Turning Insert Regrinding Focus | Milling Insert Regrinding Focus |
|---|---|---|
| Core Regrinding Parts | Main cutting edge, secondary cutting edge, nose radius | Peripheral edge, end edge, flute walls, edge chamfer |
| Precision Control Requirements | Nose radius (deviation ≤±0.1mm), angle between main and secondary edges (deviation ≤±1°) | Uniform edge sharpness, flute smoothness (Ra≤1.6μm), peripheral edge runout ≤0.02mm |
| Suitable Damage Types | Edge dullness, minor nose chipping, chip adhesion on cutting surface | Peripheral edge wear, end edge dullness, flute blockage from chip accumulation |
| Regrinding Difficulty | Lower (simpler structure, focusing on plane/arc grinding) | Higher (multi-edge, complex flute structure, requiring consistent multi-edge precision) |
Simple Explanation:
- Turning inserts focus on “linear cutting”, so regrinding prioritizes ensuring the straightness of cutting edges and nose radius precision to avoid scratches on workpiece surfaces;
- Milling inserts focus on “rotary cutting”, requiring consistent height across all peripheral and end edges. Otherwise, vibration during high-speed rotation will affect machining flatness.
4. Core Advantages and Precautions of Regrinding
4.1 3 Core Advantages of Regrinding
- Cost reduction: Regrinding costs are only 10%-25% of new inserts. A carbide insert reground 2-3 times can save over 40% in total tool expenses;
- Efficiency improvement: The regrinding cycle is usually 1-2 days, faster than purchasing new inserts (especially custom specifications), reducing production downtime;
- Waste reduction: Full utilization of remaining insert value avoids direct scrapping of slightly worn inserts, aligning with energy-saving and consumption-reducing needs.
4.2 4 Key Precautions for Regrinding
- Professional operation is mandatory: Avoid manual grinding. Use dedicated CNC tool grinders to ensure regrinding precision (e.g., edge angle, arc radius);
- Coated inserts need recoating: Regrinding removes the original coating. After repair, re-spray coatings like TiN or TiAlN; otherwise, wear resistance will drop significantly;
- Control regrinding times: Exceeding recommended times leads to insufficient insert allowance, failing to meet cutting precision and rigidity requirements, easily causing machining errors;
- Inspect after regrinding: Use calipers to check dimensions, angle rulers to verify edge angles, and conduct test cuts (on waste materials) if necessary. Confirm smooth cutting and no vibration before formal production.
5. Practical Selection Suggestions: When to Prioritize Regrinding, When to Replace Directly?
| Scenario Type | Turning Insert: Regrind? | Milling Insert: Regrind? | Decision Basis |
|---|---|---|---|
| Carbide inserts with slightly dull edges | Yes | Yes | Low regrinding cost, good performance recovery |
| Coated inserts with peeled coating but intact edges | Yes (regrind + recoat) | Yes (regrind + recoat) | Cost of recoating + regrinding is lower than new inserts |
| HSS inserts with small-area chip adhesion | Yes (1 time) | Yes (1 time) | Precision drops quickly after multiple regrinds; stop at the right time |
| Chipping area ＞0.5mm (turning)/1mm (milling) | No | No | Post-regrinding precision cannot be guaranteed |
| Insert body with cracks or severe edge defects | No | No | Regrinding risks secondary chipping, with safety hazards |
| Small-size inserts (turning ＜3mm/milling ＜5mm) | No | No | Regrinding precision is hard to control; new inserts have low unit prices |
Conclusion: Regrinding Is a “Cost-Saving Solution” but Requires “Targeted Operation”
Regrinding of turning and milling inserts (especially carbide ones) is entirely feasible. The core lies in “judging if damage is repairable, ensuring regrinding precision, and controlling regrinding times”. Turning inserts focus on nose and cutting edge angles during regrinding, while milling inserts need to balance multi-edge consistency and flute smoothness. Coated inserts must be recoated after regrinding.
As a tungsten carbide industry practitioner, when recommending tools to customers, it is advisable to share regrinding-related knowledge (e.g., regrinding cycles, allowance requirements). For customers’ old inserts, help judge if regrinding is worthwhile. A reasonable regrinding strategy can reduce costs for customers and improve tool utilization—a win-win choice.
Would you like me to sort out a regrinding parameter comparison table for turning and milling inserts, including recommended regrinding times, precision requirements, and suitable equipment for different specifications and materials, to facilitate your quick reference and customer recommendations?
Post time: Nov-26-2025
