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  2. Tap selection & optimization
  3. II. Internal thread workpiece material × Threading-Taps material
  4. Common materials for thread tool blades
  5. HSS / High Speed Steel
  6. HSS-Co 8～9% / M42 / SKH59

HSS-Co 8～9% / M42 / SKH59

M42 is typically equivalent to JIS SKH59, containing approximately 8-9% cobalt.

The common heat treatment hardness is around HRC 67, but the actual value varies depending on the manufacturer's capabilities and tool design.

M42/SKH59 possesses high red hardness and wear resistance, making it suitable for thread machining requiring high strength, difficult cutting, or high tool life. If wear resistance is the primary consideration and the M42 (SKH59) high-speed steel has a hardness as high as HRC 66-HRC 68, its toughness will be significantly reduced. In heavy-cutting, high-torque tapping applications, SKH55 (M35) remains the preferred choice due to its combination of wear resistance and high torque capacity.

Common materials for thread tool blades

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