As I browse through this forum, it seems that many of you believe that some steels can be brought to a better edge than others. Assuming optimal heat treating for cutting purposes as opposed to chopping, what steels can be made sharpest? The second half of this question is why? As always, I am most grateful for your comments and thoughts.
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How sharp can various steels be?
- Thread starter Quy4n8
- Start date
I don't think you are going to get the response you expected. It has alot more to do with blade geometry and edge thickness than what steel is being used. Now if you are talking "edge holding" capability...that is far more material related.
You can sharpen a piece of tin to shaving sharp...it may only cut a few hairs before it's dull, but it'll be sharp as hell for those first few hairs.
My sharpest knife is a BM943...blade is 154CM. Why is it so much sharper than my BM806D2. I would tend to believe it has to do with how much thinner the blade is and how the final bevels were ground. I would guess that my 806D2 would hold it's edge longer, however.
You can sharpen a piece of tin to shaving sharp...it may only cut a few hairs before it's dull, but it'll be sharp as hell for those first few hairs.
My sharpest knife is a BM943...blade is 154CM. Why is it so much sharper than my BM806D2. I would tend to believe it has to do with how much thinner the blade is and how the final bevels were ground. I would guess that my 806D2 would hold it's edge longer, however.
I agree with Drew about blade geometry and edge thickness, but not so sure about the rest. This is a quote from Joe Talmadge's Update to the Steel FAQ, which is still in draft form:
"Ability to take an edge: Some steels just seem to take a much sharper edge
than other steels, even if sharpened the exact same way. Finer-grained steels
just seem to get scary sharp much more easily than coarse-grained steels,
and this can definitely effect performance. Adding a bit of vanadium is an
easy way to get a fine-grained steels. In addition, an objective of the forging
process is to end up with a finer-grained steel. So both steel choice, and the
way that steel is handled, can effect cutting performance."
"Ability to take an edge: Some steels just seem to take a much sharper edge
than other steels, even if sharpened the exact same way. Finer-grained steels
just seem to get scary sharp much more easily than coarse-grained steels,
and this can definitely effect performance. Adding a bit of vanadium is an
easy way to get a fine-grained steels. In addition, an objective of the forging
process is to end up with a finer-grained steel. So both steel choice, and the
way that steel is handled, can effect cutting performance."
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Speaking of push cutting, the steels with the finest grain structure which are very hard can get the sharpest. The fine grain structure is necessary as you can't polish past the level of aggregates in the steel. A high hardness is not strictly needed, but it is difficult to form a high polished edge on a soft steel because of the large tendancy to form a burr. So ideally you would be looking at one of the high speed steel finishing steels at ~66 RC.
However in practice, the difference between a very fine grained steel and a very coarse grained one at a high polish is not overly significant - either can be taken to the level of push cutting hair above the skin for example. Even small changes in edge angle and quality of sharpening will easily swamp out the inherent nature of the steel. Most of the claims about steels being inherent "sharper" or cutting better is just hype and has little foundation in reality.
In regards to slicing, a softer steel with a more coarse grain structure and large carbides would be optimal. However just as in the previous case, the inherent steel qualities are a far second to the angle of the edge and the quality of sharpening as influeces on cutting ability.
In short, this isn't a practical concern. Instead it is much more worthwhile to become familiar with the influence of geometry and variance of sharpening (grits, quality) on sharpness and overall cutting ability.
-Cliff
However in practice, the difference between a very fine grained steel and a very coarse grained one at a high polish is not overly significant - either can be taken to the level of push cutting hair above the skin for example. Even small changes in edge angle and quality of sharpening will easily swamp out the inherent nature of the steel. Most of the claims about steels being inherent "sharper" or cutting better is just hype and has little foundation in reality.
In regards to slicing, a softer steel with a more coarse grain structure and large carbides would be optimal. However just as in the previous case, the inherent steel qualities are a far second to the angle of the edge and the quality of sharpening as influeces on cutting ability.
In short, this isn't a practical concern. Instead it is much more worthwhile to become familiar with the influence of geometry and variance of sharpening (grits, quality) on sharpness and overall cutting ability.
-Cliff
- Joined
- Apr 17, 2003
- Messages
- 5,283
well i have a kershaw trooper that has one hell thick blade and it holds one mean edge despite the thick blade...really it comes down to the temper of the blade IMO (like said above, its the grain structure of it), along with a good geometry for how it tapers to the edge are what makes a blade good.
just my 2 coppers...
robert.B
just my 2 coppers...
robert.B
Gentlemen, thanks for your responses. If sharpness has more to do with edge geometry, then in a push cutting application, what would be ideal? Knowing there is no ideal, what would you put the initial bevel and final bevel at, for light to moderate cutting applications? Also how thick would your blade be at the transition between initial and final bevel? In addition, would all of this be irrelevant if one used a convex ground blade?
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
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- 17,562
Richard Sommer :
The edge angle can be as low as ~10 degrees included for soft materials with the thickness behind the edge as small as 0.005". The ultimate geometry of this type is a flat ground blade with a deep hollow relief, and you then sharpen with the whole blade on the hone. Ref :
http://www.panix.com/~alvinj/HSSknife.jpg
Yes, just smooth out the sharp angle transitions into flowing curves.
-Cliff
The edge angle can be as low as ~10 degrees included for soft materials with the thickness behind the edge as small as 0.005". The ultimate geometry of this type is a flat ground blade with a deep hollow relief, and you then sharpen with the whole blade on the hone. Ref :
http://www.panix.com/~alvinj/HSSknife.jpg
Yes, just smooth out the sharp angle transitions into flowing curves.
-Cliff
- Joined
- Apr 27, 1999
- Messages
- 6,117
I guess your view on this is influenced by your point of reference. My reference standard is a hollow ground straight razor. This has a fragile edge, but is what I describe as sharp. When you get down to a really thin edge you notice that some alloys are really easy to get to a refined edge and respond well to stropping. A simple 1084 alloy carbon steel (or a similar alloy with a little vanadium in it) just keeps getting sharper as you hone and strop it. The type of hone is not too critical.
The high chrome stainless steels can be much less cooperative. The chrome can make them resist honing and can also tend to form a burr. The 440 series is often that way. If you cryo treat the blades it is supposed to reduce the grain size and help this. There are stainless alloys that feel a lot more like simple carbon steel when you sharpen them. A couple that are particularly easy to strop to a razor edge are 12C27 and AUS-8.
With the right tools and good technique you can get a sharp edge on virtually any steel. It is really helpful if you have diamond hones, japanese water stones, or strops loaded with ultra fine silicon carbide grit. These are all expensive and sophisticated solutions. If you are less sophisticated and well equiped you will definitely find some alloys easier to sharpen than others.
The high chrome stainless steels can be much less cooperative. The chrome can make them resist honing and can also tend to form a burr. The 440 series is often that way. If you cryo treat the blades it is supposed to reduce the grain size and help this. There are stainless alloys that feel a lot more like simple carbon steel when you sharpen them. A couple that are particularly easy to strop to a razor edge are 12C27 and AUS-8.
With the right tools and good technique you can get a sharp edge on virtually any steel. It is really helpful if you have diamond hones, japanese water stones, or strops loaded with ultra fine silicon carbide grit. These are all expensive and sophisticated solutions. If you are less sophisticated and well equiped you will definitely find some alloys easier to sharpen than others.