Uniform Hardness. Surface to Center.

NAK55 is Daido’s pre-hardened mold steel for plastic molds, rubber molds, jigs and fixtures, and press dies.

NAK55 is supplied pre-hardened, so the block goes to the machine with no hardening cycle and no stress relieving in between. Hardness distribution stays uniform between surface and interior, through to the center of the section.

One Grade Across Molds, Dies, and Fixtures

• Pre-Hardened Delivery: The block arrives at 38 to 42 HRC, ready to machine with no hardening cycle.
• Faster Machining: NAK55 machines 30 to 40 percent faster than P20.
• Uniform Hardness: The 40 HRC reading holds between surface and interior, through to the center of the section.
• No Stress Relieving: The grade never needs stress relieving.
• Clean Weld Repair: The heat-affected zone gets softer rather than harder, and re-age hardening brings the repair back to 40 HRC with no witness line.
• Easy EDM Cleanup: The EDM layer is easy to remove, and Daido publishes a mirror-finishing order for the grade. 

NAK55 is a general purpose plastic molding material for mass production. The published data sheet reads 182,000 psi tensile strength and 146,500 psi yield at 40 HRC.

The grade decision is made before the first cut. IMS has been Daido’s U.S. partner since 1991, and its application engineers match NAK55 to the mold, the resin, and the production run.