AB Coltellerie

Help Desk: Can I get more information on the steels you use (ATS34, AISI420, ...)?

We currently use ATS 34 steel for some Italian Stiletto knives, AISI 440B for the New Age knives and AISI 420 for all the other knives. Here follows the description of these three kinds of steel, extracted from Joe Talmadge's Steel FAQ.

• AISI 420: Lower carbon content (<.5%) than the 440 series makes this steel extremely soft, and it doesn't hold an edge well. It is used often for diving knives, as it is extremely stain resistant. Also used often for very inexpensive knives. Outside salt water use, it is too soft to be a good choice for a utility knife.
• AISI 440A - 440B - 440C: The carbon content (and hardenability) of this stainless steel goes up in order from A (.75%) to B (.9%) to C (1.2%). 440C is an excellent, high-end stainless steel, usually hardened to around 56-58 Rc. All three resist rust well, with 440A being the most rust resistant, and 440C the least. The SOG Seal 2000 is 440A, and Randall uses 440B for their stainless knives. 440C is fairly ubiquitous, and is generally considered the penultimate general-use stainless (with ATS-34 being the ultimate). If your knife is marked with just "440", it is probably the less expensive 440A; if a manufacturer had used the more expensive 440C, he'd want to advertise that. The general feeling is that 440A (and similar steels, see below) is just good enough for everyday use, especially with a good heat treat (we've heard good reports on SOG's 440A heat treat). 440-B is a very solid performer and 440-C is excellent.
• ATS-34 - 154-CM The hottest high-end stainless right now. 154-CM is the original American version, but for a long time was not manufactured to the high quality standards knifemakers expect, and so is not used often anymore. Late-breaking news is that high-quality 154-CM may again be available. ATS-34 is a Hitachi product that is very, very similar to 154-CM, and is the premier high quality stainless. Normally hardened to around 60 Rc, it holds an edge very well and is tough enough even at that high hardness. Not quite as rust resistant as the 400 series above. Many custom makers use ATS-34, and Spyderco (in their high-end knives) and Benchmade are among the production companies that use it.