Q: How do hardness and red hardness differ among HSS 4241, 4341, M2, M35 and M42 drill bits?
A: Heat treatment determines the hardness and toughness of HSS drill bits, while red hardness describes their ability to retain hardness at elevated cutting temperatures.
| HSS Grade | Working Hardness | Red Hardness / Heat Resistance | Typical Applications |
|---|---|---|---|
| HSS 4241 | 60–61 HRC | Low | Mild steel, thin sheet metal, DIY drilling |
| HSS 4341 | 62–64 HRC | Moderate; better than 4241 | General steel, cast iron |
| HSS M2 (6542) | 62–64 HRC | Approx. 47–49 HRC at 600°C* | Carbon steel, alloy steel, general industrial drilling |
| HSS M35 (Co5) | 64–66 HRC | Reported 63–65 HRC after exposure to 625°C* | Stainless steel, alloy steel |
| HSS M42 (Co8) | 67–70 HRC* | Very high; generally strong hot-hardness retention | Heat-resistant alloys, demanding metal drilling |
* Technical values supplied for review. M2 and M35 figures may represent different measurement conditions and are not directly comparable. The M42 hardness range also requires verification against actual production data before publication.
Key Takeaway
Hardness determines resistance to deformation and wear, while red hardness helps maintain cutting performance as the cutting edge becomes hot.Choosing the right HSS grade and applying proper heat treatment are essential for reliable drilling performance.