Knife Making :: Blade Steel
The blade of course is the heart of the knife. If the steel isn't right for the intended use then everything else is lost. Knife steel selection is a process of trade offs just like everything else in life.
Hatchets and chisels are made from low alloy steels because toughness is the over riding consideration. Taps, dies, drill bits and bearings are made from tool steel. These steels are designed to form and cut other metals. Most custom knife blades are selected from this category. The challenge is to select the steel that has the right balance of toughness and wear resistance and to grind and heat treat it so that the full potential is met.
As new steels are introduced I have discontinued the use of some of my old favorites (ATS 34, 440-C 420HC). My current production is made up of these seven tool and die steel grades: 154CM, CPM 154, CPM, S90V, CPM S30V, CPM 10V, CPM S110V, CPM M4.(i)
I now use 154CM, CPM154, CPMS30V and Bohler N690 for fillet knives. All are very stain resistant, have very good edge holding, and ductility. The majority of my hunting knives the last couple of years have been made with CPM S90V, CPM 10V, CPM S110V and Bohler K294, K390 and M390. I use CPM 154, N690 and CPM S-30V for kitchen knives.
The particle metal steels (PM) makeup the largest percentage of my production. These are produced by Crucible Materials and Bohler-Uddeholm.
All of the PM steels have a high percentage of very hard; very fine carbide particles in the steel matrix. CPM S90V was introduced in 1997 as an upgrade for CPM S60V. It has a higher attainable hardness for improved wear resistance.
(i) CPM is an acronym for Crucible Particle Metalurgy. The S prefix stands for stainless steel.See also the Crucible Industries website for more detail.
I worked in conjunction with Crucible Materials to pioneer the use of CPM S90V for knife blades. I remain one of the few makers currently offering it because very few are set up to heat treat this grade. I built a high temperature, precisely controlled furnace and developed the techniques required for consistent results.
I heat treat CPM S90V to a finish hardness of (RC 59-61). CPM S90 V is still a very good choice for the ultimate hunting blade but in 2009, Crucible introduced an additional grade. This one is CPM S110V. In addition to the 10% Vanadium in S-90V, Cobalt, Molybdenum and Niobium have been added. All these alloys combine to form a complex carbide that provide excellent wear resistance. Crucible also claims some additional corrosion resistance.
This grade still requires the same attention to heat-treating as S-90V, but the attainable hardness is a bit higher. My initial work with CPM S110V, and subsequent field testing has shown that a Rockwell hardness of 62 to provide a good balance of hardness and edge strength.
CPM 10V has about the same alloy content as CPM S-90V with the exception of Chromium. Five percent Chromium is not enough to make it stain resistant. This however allows a higher attainable hardness (RC 63-64) with the resultant further increase in wear resistance and edge holding.
CPM 10V has been the edge holding standard for me ever since I first tried it 20 plus years ago. I currently offer this steel but only for users who ask for it specifically and understand the trade offs associated with its use.
In 2010 Bohler-Uddehlom, a Austrian/Swedish steel company decided to offer knife grade steels to both custom makers and production companies. I have used Bohler N690 for fillet and kitchen knives and found it to have high corrosion resistance, be an aggressive cutter and is easy to sharpen. It is very similar to the better known Japanese VG10 grade.
B-U has also made two A11 grades available that are very similar to CPM 10V. These are K390 and K294. They are pretty much interchangeable with 10V and have found them to make excellent hunting knife blades.
Crucible made a heat of CPM 125V a few years ago and I purchased enough to make about 20 knife blades. To date I have only made a few hunters for test blades. Performance was excellent but due to fabrication difficulties, I have pretty much dropped this one.
It looks like at this point that CPM S-110V has all the great potential qualities that CPM S-125V did. It is difficult to grind and finish but is well worth the effort. My cutting tests on Manila rope show a very high wear resistance. It is in about the same category as 10V for edge holding and is stainless as a bonus.
Please refer to the articles section for more information on these steels.