Can End Mills Be Reground ?

End mills, especially those made of tungsten carbide cemented carbide, can be reground. In fact, proper regrinding is a key way to extend tool life and reduce production costs. For minor wear, edge dullness, and other issues that occur during machining, professional regrinding can restore their cutting performance, eliminating the need to replace them with new tools directly. However, regrinding requires certain prerequisites (such as no cracks in the tool body and damage within acceptable limits) and must control regrinding accuracy and frequency. This article will answer core questions from four dimensions—”whether regrinding is possible”, “prerequisites for regrinding”, “core of regrinding”, and “advantages and precautions”—using plain language and clear tables, helping industry practitioners quickly grasp practical knowledge about end mill regrinding.

1. Clear Conclusion: End Mills Can Be Reground, with Material and Damage Degree as Key Factors

Not all end mills are suitable for regrinding. The key depends on tool material and damage condition, among which tungsten carbide end mills have the highest regrinding value.

Tool Material	Suitable for Regrinding?	Recommended Regrinding Times	Core Reason
Tungsten Carbide	Yes (priority for regrinding)	3-5 times	High hardness and wear resistance; performance after edge repair is close to new tools
High-Speed Steel (HSS)	Yes (limited regrinding)	1-2 times	Good toughness but lower hardness; precision decreases rapidly after multiple regrindings
Coated Tools	Yes (needs recoating)	2-3 times	Regrinding removes the coating; re-coating is required after repair to ensure performance

Key Judgment: Only end mills that meet “damage is limited to the cutting edge area, no cracks in the tool body, and no deformation of the shank” are worth regrinding. If there is large-scale chipping (chip size exceeding 0.5mm), tool body cracks, or core deformation, the precision after regrinding cannot be guaranteed, and it may affect machining quality. It is recommended to replace them directly.

2. Prerequisites for Regrinding: Only These 3 Conditions Are Suitable

End mill regrinding is not “repair whenever there is damage”. It needs to meet the following prerequisites; otherwise, regrinding is of little significance:

1. Damage type is “repairable”: Only edge dullness, minor wear, or small-area chip adhesion (no chipping or chip size ≤0.3mm). Such damage can restore the sharpness of the cutting edge through regrinding;
2. Tool body structure is intact: No cracks or bending deformation in the tool body, and no severe wear in the flutes (such as narrowing of flute width or collapse of flute walls). Otherwise, smooth chip evacuation cannot be guaranteed after regrinding;
3. Sufficient size allowance: New tools have a certain regrinding allowance (tungsten carbide end mills usually have a diameter allowance of ≥0.2mm). The diameter reduction after multiple regrindings should not exceed 5% of the original diameter to avoid affecting machining dimensional accuracy.

Counterexample: If an end mill has edge chipping exceeding 1mm due to high-speed collision, or there are through cracks in the tool body, even regrinding cannot restore its rigidity. Vibration and chipping are likely to occur during machining, which may damage the workpiece and equipment.

3. Core Content of Regrinding: Mainly Repair These Parts to Restore Cutting Performance

The core of end mill regrinding is “restoring the geometric shape and sharpness of the cutting edge”. Focus on repairing 3 key parts without complex adjustments:

1. Cutting edge: Remove the dull layer and chip adhesion marks on the edge, and regrind a sharp edge (to avoid “extrusion” instead of “cutting” during machining);
2. Rake angle/relief angle: Restore the originally designed rake angle (to control cutting resistance) and relief angle (to reduce friction with the workpiece). The angle deviation must be controlled within ±0.5°;
3. Flutes: Clean residual chips and adhered material in the flutes, and regrind the smoothness of the flute walls to ensure smooth chip evacuation and avoid tool overheating due to chip accumulation.

Simple Inspection: After regrinding, gently touch the cutting edge with a gloved hand—there should be no “burr feeling” and the edge should be straight. When illuminated with strong light, there should be no obvious reflection on the edge (reflection indicates dullness), which is considered basically qualified.

4. Advantages and Precautions of Regrinding: Obvious Benefits, but Avoid These Pitfalls

4.1 3 Core Advantages of Regrinding

• Cost reduction: Regrinding costs are only 10%-30% of the price of a new tool. A tungsten carbide end mill reground 3 times can save more than 50% of tool expenses in total;
• Quick adaptation: For slightly worn tools, the regrinding cycle (usually 1-2 days) is shorter than purchasing new tools, reducing production downtime;
• Inventory reduction: There is no need to stock a large number of spare tools. Existing tools can meet regular machining needs through regrinding, reducing inventory occupation.

4.2 3 Key Precautions for Regrinding

1. Professional operation is a must: Avoid manual grinding (prone to angle deviation and uneven edges). Special tool regrinding equipment (such as CNC tool grinders) is required to ensure accuracy;
2. Control regrinding times: Tungsten carbide end mills can be reground at most 3-5 times. Excessive regrinding will reduce the tool body diameter and rigidity, affecting machining dimensional accuracy;
3. Inspection after regrinding: Use calipers to check the tool diameter, angle rulers to verify the rake/relief angles, and conduct test cuts (on waste materials) if necessary. Confirm smooth cutting and no vibration before putting it into formal production.

5. Practical Selection Suggestions: Which End Mills Should Be Prioritized for Regrinding?

Scenario Type	Worth Regrinding?	Decision Basis
Tungsten carbide end mill, slightly dull	Yes	Wear-resistant material; performance after regrinding is close to new tools, with great cost advantages
HSS end mill, small-area chipping	Yes (1 time)	Low regrinding cost, but precision decreases rapidly after multiple regrindings
Coated end mill, coating peeled but edge intact	Yes (regrind + recoat)	Cost of recoating + regrinding is lower than new tools, with high cost performance
Tool body with cracks, severe chipping	No	High regrinding risk, prone to machining failures
Small-diameter end mill (≤3mm)	No	Regrinding accuracy is difficult to control, and new tools have low unit prices

Conclusion: End Mill Regrinding Is a “Cost-Effective and Practical” Choice, but Requires “Targeted Regrinding”

Regrinding of end mills, especially tungsten carbide ones, is entirely feasible. For slightly worn tools, regrinding is far more cost-effective than direct replacement. The key is to grasp the three principles: “no damage to the tool body, guaranteed precision, and no excessive regrinding times”. Professional regrinding can restore cutting performance, reduce production costs, and reduce inventory pressure.

As a tungsten carbide industry practitioner, it is recommended to inform customers of regrinding-related knowledge (such as regrinding cycles and allowable times) when recommending tools. For customers’ old tools, you can help judge whether they are worth regrinding.

Would you like me to sort out a parameter comparison table for end mill regrinding, including recommended regrinding times, precision requirements, and suitable equipment for end mills of different diameters and materials, to facilitate your quick reference and suggestions for customers?