Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
In the middle of doing some work on cardboard with the small Sebenza vs a few other knives I saw a few interesting aspects of performance, most of which I knew about, most of which Alvin and Miked talked about on rec.knives. So I made some effort to quantify them in a little detail and ended updoing a fairly large volume of work.
First was angle and edge retention, I compared the small Sebenza to a Meadowlark with the edges at 5 degrees and cut some cardboard, repeating the cutting several times. It was impossible to say which knife had better edge retention because I was hand honing the edges and the angle was having a massive influence.
At low angles it was very difficult to get clean edges, under mag the edge was breaking apart revealing large chips (0.1 mm were visible in some sections). In use the edges also further developed large chips and the edge rippled grossly, enough to see by eye. Which one tended to do best was which one had the higher honing angle basically and it could make a many to one difference.
I then cut the edges at 15 degrees on the Sharpmaker, microbevel, and did push cuts and the edge rippling was much less evident, this makes sense given the larger angle and the blades cut far more cardboard (several times over). However when the edges were increased to 20 degrees the lifetime of the edge was worse, so there is a "sweet spot" in regards to angle.
I think this can be explained by noting that at lower edge angles the cutting ablity is higher and the slicing aggression inherently higher for a couple of reasons. As you go really low the strength is reduced too far and the edge just bends/ripples too much and the edge retention is really low, but as you increase it too high you lose too much cutting ability and slicing aggression and you can't cut very much material either.
It would be interesting to compare a few stock blades with a range of angles, say 5,10,15,20, on both push cutting and slicing because if the above presupposition holds true, there should be a difference in how they respond to the angles in regards to edge retention.
I then compared slicing cardboard vs push cuts and the edge retention was very different. On push cuts the small Sebenza and the Meadowlark were pretty much identical, and there was no advantage to the much more expensive S30V blade, on slicing however the Sebenza was significantly ahead. This can be argued for based on carbide / wear. I also compared the Sebenza to two different Temperances, multiple times for each one and found the same thing.
What would be interesting would be to compare the small Sebenza to both harder blades with less wear resistance as well as softer blades with more wear resistance and thus see how much of an effect each one makes. I have some blades to check some of these things and will look at them as time allows.
As a side note, the Sebenza with a high relief grind is one of the easiest knives I have to sharpen. The deep hollow grinds allows the primary edge to be reset very easily and the steel doesn't burr heavily. I would also like to compare this to S30V at a few more HRC points and see the difference in regards to the above points (angles, push/slice edge retention).
Note in regards to generality, slicing cardboard tends to hold well to slicing most materials, and push cutting cardboard tends to hold well for push cutting most materials, thus trials ran slicing ropes or whittling wood tend to agree with the above loose laws of behavior, performance seems to be critically influenced by the nature of the cutting more so than the media, assuming you can of course do that type of cutting on the media, you can't for example actually slice wood to any degree with a knife.
However going directly from cardboard to ropes on a slice is a bit complicated in regards to grits because slicing ropes tends to benefit pretty straightforwardly on decreasing grit but in cardboard it is more complicated because even on heavy slicies there is some push cutting so again there is a sweet spot in regards to finish.
-Cliff
First was angle and edge retention, I compared the small Sebenza to a Meadowlark with the edges at 5 degrees and cut some cardboard, repeating the cutting several times. It was impossible to say which knife had better edge retention because I was hand honing the edges and the angle was having a massive influence.
At low angles it was very difficult to get clean edges, under mag the edge was breaking apart revealing large chips (0.1 mm were visible in some sections). In use the edges also further developed large chips and the edge rippled grossly, enough to see by eye. Which one tended to do best was which one had the higher honing angle basically and it could make a many to one difference.
I then cut the edges at 15 degrees on the Sharpmaker, microbevel, and did push cuts and the edge rippling was much less evident, this makes sense given the larger angle and the blades cut far more cardboard (several times over). However when the edges were increased to 20 degrees the lifetime of the edge was worse, so there is a "sweet spot" in regards to angle.
I think this can be explained by noting that at lower edge angles the cutting ablity is higher and the slicing aggression inherently higher for a couple of reasons. As you go really low the strength is reduced too far and the edge just bends/ripples too much and the edge retention is really low, but as you increase it too high you lose too much cutting ability and slicing aggression and you can't cut very much material either.
It would be interesting to compare a few stock blades with a range of angles, say 5,10,15,20, on both push cutting and slicing because if the above presupposition holds true, there should be a difference in how they respond to the angles in regards to edge retention.
I then compared slicing cardboard vs push cuts and the edge retention was very different. On push cuts the small Sebenza and the Meadowlark were pretty much identical, and there was no advantage to the much more expensive S30V blade, on slicing however the Sebenza was significantly ahead. This can be argued for based on carbide / wear. I also compared the Sebenza to two different Temperances, multiple times for each one and found the same thing.
What would be interesting would be to compare the small Sebenza to both harder blades with less wear resistance as well as softer blades with more wear resistance and thus see how much of an effect each one makes. I have some blades to check some of these things and will look at them as time allows.
As a side note, the Sebenza with a high relief grind is one of the easiest knives I have to sharpen. The deep hollow grinds allows the primary edge to be reset very easily and the steel doesn't burr heavily. I would also like to compare this to S30V at a few more HRC points and see the difference in regards to the above points (angles, push/slice edge retention).
Note in regards to generality, slicing cardboard tends to hold well to slicing most materials, and push cutting cardboard tends to hold well for push cutting most materials, thus trials ran slicing ropes or whittling wood tend to agree with the above loose laws of behavior, performance seems to be critically influenced by the nature of the cutting more so than the media, assuming you can of course do that type of cutting on the media, you can't for example actually slice wood to any degree with a knife.
However going directly from cardboard to ropes on a slice is a bit complicated in regards to grits because slicing ropes tends to benefit pretty straightforwardly on decreasing grit but in cardboard it is more complicated because even on heavy slicies there is some push cutting so again there is a sweet spot in regards to finish.
-Cliff
