Higher HRC does not necessarily make a better knife, regardless of toughness. S7 has been around for quite a long time. It HAS been used in knives, most people just don't go back to it. That
is anecdotal evidence. Charpy tests alone do not prove that a steel will make a better knife, no matter the HRC.
Consider some of the other Crucible steels that
are being used for knives, like S30V, S90V, CPM 3V etc. Why did these catch on and not your beloved S5 and S7 steels? S5 may well be the perfect steel for your specific application - but when someone asks a general question about two specific oil quenching carbon steels, answering with a simple "use S5 for 'shock applications'" if pretty well useless.
Crucible does not list S5 or S7 as a high speed steel for cutting tools, it does not list them as stainless tool steels... S7 and S5 are listed as a die, mold and tool steels for metal
forming and
plastics. These are designed for a very different sort of impact than the edge of a "tough" knife.
Here is some info for you from Crucible's orange book -
Crucible Tool Steel and Specialty Alloy Selector Pg. 77-78 said:
S5
Typical Applications
Heading Tools
Punches
Chisels
Shear Blades
Rivet Sets
Concrete Breakers
Hand Tools
Hammers
Typical Properties
300F 60-61RC 49 Ft-Lbs.
400F 58-60RC 138 Ft-Lbs.
500F 58-59RC 146 Ft-Lbs.
600F 57-58RC 142 Ft-Lbs.
700F 56-57RC 156 Ft-Lbs.
Crucible Tool Steel and Specialty Alloy Selector Pg. 80-81 said:
S7
Typical Applictions
Punches and Dies Subject to Heavy Impact
Wire EDMed Punches & Dies
Warm Forgin/Heading Dies
Plastic Inject Molds
Shear Blades
Typical Properties
300F 59RC 85Ft-Lbs.
400F 57RC 125Ft-Lbs.
500F 55RC 125Ft-Lbs.
600F 54RC 115Ft-Lbs.
-
1100F 47RC 190Ft-Lbs.
You'll note that the only blade application in both of these steels is shear blades. Now that I've gone and posted these awing toughness numbers - tell me, how do they make a knife better if it's not being used solely to bludgeon through things?
You'll note that even with these great facts and figures about HRC and Charpy values we know nothing of abrasion resistance, something of particular interest to folks whose products primary use revolves around, you guessed it, abrasion.
Some listed applications for other steels that Crucible sells (sold?) that are common for knife blades:
Crucible Tool Steel and Specialty Alloy Selector Pg. 50 said:
Trim Dies
Wear Inserts
Blanking Dies and Punches
Engraving Tools
Paper Knives
Taps
Industrial Knives ad Slitters
Scrap Choppers
Broaches
Shaper Cutters
Shaving Cutters
Milling Cutters
Threading Dies
Industrial Knives, Slitters, and Cutters
Long-wearing Specialty Cutlery
Wear Components for Food and Chemical Processing
Knives
Surgical Tools
Cutlery
Looks a little different yes? Interesting bit of info - the description on S7 says it offers "good wear resistance", S5 has no such description. It may be a stretch, but one might assume that since these steels are not only in the same family, but also listed consecutively in the Crucible book that S5 has less wear resistance than S7. If we extrapolate this further, we can look at the datasheet for CPM 3V and see a chart that shows 3V, A2, D2 and CPM M4 all having significantly higher wear resistance values and a far less significant difference in toughness between CPM 3V and S7.
3V data sheet @ Crucible
http://www.crucibleservice.com/datash/ds3Vv5b.pdf
OK, now that we've seen that not only can I read the same data sheets you can, but I also own them, can we get on to the part where you show us properties in S5 that are desirable in a knife?
One can spend too much time looking at numbers on the internet or a book and not enough time trying to make them do something for him. Have you made knives with any of the steels that I've listed? What application were/are they used in? How did they compare to other steels in this discussion? Or, was this all just done up on paper and never actually tested?
