Bob Smalser
12-15-2004, 11:20 AM
I been asked to do an article that involves, among other things, talking about tool steel.
Being predjudiced as all get-out on the subject...but with ignorance to match...here's what I've written in an attempt to be objective and I'd like y'all to tear it apart:
What you need to know about steel.
High Carbon Steel
After the Henry Bessemer process of making steel was developed and refined during the middle 1800’s to reliably produce large quantities of high-carbon tool steel inexpensively, such steel became the mainstay of edge tool production that continues today. “Warranted Cast Steel”, “Sheffield Steel”, modern 0-1 Tool Steel, “Swedish Steel”, and others. (It was the Swedish iron ore, not necessarily their steel that was better, as it lacked the phosphorous that makes steel brittle.) Many of the chisels made during Bessemer’s lifetime still serve admirably today, as properly forged carbon steel takes an excellent edge while is very easy to resharpen using traditional composite, water or oilstones.
Chrome Vanadium Steel
A modern, shiny tool steel commonly seen in lower grades of chisels. The chromium and vanadium add hardness, toughness and rust resistance, and if properly made, can take a good cutting edge. They are generally more difficult to sharpen than carbon steel, and in lower tool grades can be impossible to obtain an “excellent” cutting edge.
High Speed Steel
M-2 and other formulations. Chromium, tungsten, molybdenum and vanadium are added to resist softening when the steel is overheated during use or sharpening on a high-speed grinder. Used primarily in drill bits and lathe tools, this steel is hard, tough, easy and fast to grind, holds its cutting edge considerably longer than carbon steel, but is very difficult to hand hone and doesn’t take as fine an edge.
A-2 Steel
The modern compromise. High carbon steel with chromium and molybdenum added in smaller amounts than some other modern steels, but sufficient to add some toughness, hardness and longer edge life at minimum expense to the quality of the cutting edge and ease of sharpening. I find these blades only slightly more difficult to hand hone on traditional oil stones than carbon steel, and it is doable without resorting to the modern diamond pastes often recommended. I also find A-2 blades take a very good edge and hold it as long or slightly longer than my best prewar carbon tools.
Rockwell Hardness
More compromises. The Rockwell index is simply a hardness test of the final, tempered steel. Chisels available today can range from RC 56 (relatively soft) to RC 64 (relatively hard). Softer steel is easier to sharpen but doesn’t hold its edge as long as harder steel, which takes longer to sharpen but holds its edge longer. Chisels in the RC 60 range and above can also be brittle, if not during use then when you accidentally knock one on a concrete floor and find you have a badly chipped edge that must be severely reground. As a practical matter working at or close to a bench, I find chisels so fast and easy to touch up on the stones, that harder isn’t better for me - my preference is the sharpest cutting edge I can hone, but hone easily. In my plane irons however, it is real convenient to not have to dismantle, hone, reassemble and adjust any more often than I absolutely have to, and depending on the plane, that preference may be secondary to my best cutting edge.
Forging – does it make a difference?
I think so. Every time a coke-fired, red-hot billet of carbon tool steel is hit with the trip hammer, it is “refined” in blacksmith parlance, meaning that more carbon from the coke and in the steel is worked into a smaller area, and it’s the carbon in steel that provides the excellent cutting edge. Modern tools are generally hit 4 times or so, whereas tools made by older factory methods before WWII were hit as many as 30 times, and hand-forged tools many more times than that.
As a practical matter in edge tools, the differences are often subtle and subjective, but are certainly there. Almost all my older professional friends in the woodworking trades much prefer the best prewar makes of chisels to new factory chisels, however expensive. Hand forged, best-quality steel is the mainstay of legions of knowledgeable Japanese tool woodworkers, and toolmaker Barr Quarton wouldn’t still be in business after over 20 years of hand-forging edge tools if he didn’t have a superior product.
Being predjudiced as all get-out on the subject...but with ignorance to match...here's what I've written in an attempt to be objective and I'd like y'all to tear it apart:
What you need to know about steel.
High Carbon Steel
After the Henry Bessemer process of making steel was developed and refined during the middle 1800’s to reliably produce large quantities of high-carbon tool steel inexpensively, such steel became the mainstay of edge tool production that continues today. “Warranted Cast Steel”, “Sheffield Steel”, modern 0-1 Tool Steel, “Swedish Steel”, and others. (It was the Swedish iron ore, not necessarily their steel that was better, as it lacked the phosphorous that makes steel brittle.) Many of the chisels made during Bessemer’s lifetime still serve admirably today, as properly forged carbon steel takes an excellent edge while is very easy to resharpen using traditional composite, water or oilstones.
Chrome Vanadium Steel
A modern, shiny tool steel commonly seen in lower grades of chisels. The chromium and vanadium add hardness, toughness and rust resistance, and if properly made, can take a good cutting edge. They are generally more difficult to sharpen than carbon steel, and in lower tool grades can be impossible to obtain an “excellent” cutting edge.
High Speed Steel
M-2 and other formulations. Chromium, tungsten, molybdenum and vanadium are added to resist softening when the steel is overheated during use or sharpening on a high-speed grinder. Used primarily in drill bits and lathe tools, this steel is hard, tough, easy and fast to grind, holds its cutting edge considerably longer than carbon steel, but is very difficult to hand hone and doesn’t take as fine an edge.
A-2 Steel
The modern compromise. High carbon steel with chromium and molybdenum added in smaller amounts than some other modern steels, but sufficient to add some toughness, hardness and longer edge life at minimum expense to the quality of the cutting edge and ease of sharpening. I find these blades only slightly more difficult to hand hone on traditional oil stones than carbon steel, and it is doable without resorting to the modern diamond pastes often recommended. I also find A-2 blades take a very good edge and hold it as long or slightly longer than my best prewar carbon tools.
Rockwell Hardness
More compromises. The Rockwell index is simply a hardness test of the final, tempered steel. Chisels available today can range from RC 56 (relatively soft) to RC 64 (relatively hard). Softer steel is easier to sharpen but doesn’t hold its edge as long as harder steel, which takes longer to sharpen but holds its edge longer. Chisels in the RC 60 range and above can also be brittle, if not during use then when you accidentally knock one on a concrete floor and find you have a badly chipped edge that must be severely reground. As a practical matter working at or close to a bench, I find chisels so fast and easy to touch up on the stones, that harder isn’t better for me - my preference is the sharpest cutting edge I can hone, but hone easily. In my plane irons however, it is real convenient to not have to dismantle, hone, reassemble and adjust any more often than I absolutely have to, and depending on the plane, that preference may be secondary to my best cutting edge.
Forging – does it make a difference?
I think so. Every time a coke-fired, red-hot billet of carbon tool steel is hit with the trip hammer, it is “refined” in blacksmith parlance, meaning that more carbon from the coke and in the steel is worked into a smaller area, and it’s the carbon in steel that provides the excellent cutting edge. Modern tools are generally hit 4 times or so, whereas tools made by older factory methods before WWII were hit as many as 30 times, and hand-forged tools many more times than that.
As a practical matter in edge tools, the differences are often subtle and subjective, but are certainly there. Almost all my older professional friends in the woodworking trades much prefer the best prewar makes of chisels to new factory chisels, however expensive. Hand forged, best-quality steel is the mainstay of legions of knowledgeable Japanese tool woodworkers, and toolmaker Barr Quarton wouldn’t still be in business after over 20 years of hand-forging edge tools if he didn’t have a superior product.