For single-step precision punching of steel, especially products with teeth, you must use 8566 anti-chipping steel; otherwise, the punch will chip so badly you’ll start questioning your life choices.
Mr. Zhang came to consult with me yesterday. He’s precision punching 4mm-thick pickled sheet metal, and the product features many small serrations. He’s tried SKH9, SKH51, DC53, and PM23 for the punches, and has adjusted the hardness up and down, but the punches still chip easily, making it impossible to produce the parts. At best, he can punch a few thousand pieces; sometimes, the punches chip after just a few hundred. He asked me what tool steel to use for precision punching dies.
Fine-blanking dies require a fully polished surface and very tight clearances, placing extremely high demands on the die steel’s resistance to chipping, wear resistance, and non-stick properties. This is especially true for single-step fine-blanking, where the punch must be forced into the material. Since the punch has sharp corners—where pressure is extremely high—the die is highly prone to chipping. Therefore, resistance to chipping should be the top priority when selecting die steel, followed by high hardness.
Mr. Zhang is performing single-step fine blanking of 4mm pickled sheet metal, and the product features fine teeth. He is using DC53, SKH9, and SKH51 for the punch—this is an incorrect material selection. DC53, SKH9, and SKH51 are all high-carbon steels and are very brittle. This is especially true for SKH9 and SKH51, these are general-purpose high-speed steels (W6Mo5Cr4V2) with a hardness of 62–64 HRC and excellent wear resistance. However, conventionally cast high-speed steels suffer from severe segregation, resulting in a microstructure riddled with microscopic cracks invisible to the naked eye. As high-alloy materials, they are hard but brittle, with insufficient toughness to meet the toughness requirements of fine blanking dies.
Using PM23 powdered high-speed steel that costs several hundred yuan per kilogram is a waste of money—it reflects a flawed material selection approach, and the outcome is bound to be wrong. If it costs only a few hundred yuan now but breaks after just a few thousand punches, this further confirms that this material choice is unreasonable. For harsh working conditions involving narrow edges and sharp corners like these, you must use 8566 chipping-resistant steel.
8566 is a proprietary anti-chipping steel from Yuhui Mold Steel. Its resistance to chipping is four times that of SKH-9 high-speed steel and twice that of D2, with a hardness of 58–60 HRC. It is primarily designed to address chipping issues that high-hardness mold steels such as D2, DC53, and SKH9 cannot resolve. In particular, for stainless steel stamping, sharp-corner stamping, thick-sheet stamping, fine-blanking dies, narrow-edge stamping, and even single-step fine-blanking where the punch width is less than the sheet thickness—especially when dealing with thick sheets—where conventional die steels fail to prevent chipping, 8566 is the solution.
Mr. He used a fine-blanking machine to perform single-step fine-blanking of a 7mm-thick 45 steel gear ring. When using DC53, the punch corners chipped after only 2,000 shots, with each chip measuring 3–5 mm. Repairing the punch required wire cutting off a section before grinding, which was time-consuming and wasteful of the punch. After switching to LD mold steel and reducing the hardness, the punch could still only produce 5,000 parts before the corners began to chip off—each time losing 2–3 mm. To repair the punch, a section still had to be cut off first. When they switched to the more ductile W360, the wear resistance proved too poor; the punch wore out before reaching 5,000 parts, failing to achieve the desired precision blanking results.
Mr. He said, “I operate a precision punching machine, and efficiency is what I need. The punches for precision punching machines are all cut using slow-wire EDM, which is very expensive. But if the punch chips and becomes scrap before reaching 5,000 products, I have to stop the machine to wire-cut and grind the punch. Not only can I not afford the punches, but even if I could, this level of inefficiency is simply unacceptable.” After he contacted me and began using 8566 anti-chipping steel, a single punch could produce 25,000 parts without chipping. Compared to his previous best-performing LD punches, which lasted 5,000 cycles, the 8566 steel increased die life by five times.
A fivefold increase in punch life means five fewer punches to machine and five fewer die changes—this is the ideal scenario for improved efficiency and reduced costs, demonstrating the high cost-performance ratio of 8566 anti-chipping steel.
Mr. Zhang performs single-step precision punching of 4-thick pickled sheet metal using SKH9, SKH51, DC53, PM23—but in all four cases, the punches chipped after just a few hundred to a thousand strokes, a problem you’ve been unable to solve. You should follow Mr. He’s example and use 8566 anti-chipping steel.
Mr. He performs single-step fine blanking of 7mm-thick 45 steel gear rings—a material thicker and harder than yours, also featuring sharp corners typical of gear products, with a die structure similar to yours—and achieves 25,000 strokes. You’re precision stamping 4mm pickled sheet metal in a single step—using 8566 will definitely last well beyond 25,000 strokes. To solve your die chipping problem and improve stamping efficiency, you should definitely give 8566 anti-chipping mold steel a try.
Using 8566 die steel for punch chipping makes all the difference—it’s like night and day.
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Wu Dejian’s tool steel, the chief of staff of the user, bought everything he had used.