Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
To examine the difference in corrosion resistance, the knives were dipped in lemon juice for a quarter inch back from the edge. The blades were tested for sharpness before the soaking, after two hours (the juice was applied again at the one hour mark), and then after some rope (3/8" hemp) cutting. The results :
Sharpness before the soaking, as measured on 1/4" poly (length of blade needed to cut the cord) :
D2 -> 1.10 +/- 0.16 cm
VG -> 1.14 +/- 0.22
A8 -> 1.10 +/- 0.09
All blades have equally sharp edges at the start. The knives were sharpened using a DMT 600 grit rod set at 22 degrees. After a two hour soak the AUS-8A (A8) and VG-10 blade looked no different, no sign of corrosion by eye or under magnification. The edge bevel grinds lines were still clear under the scope. The D2 blade however had a distinct patina in all the contact area and parts of the edge bevel were solid black with oxidation (~one cm lengths). Checking the edge under magnification on the D2 knife, the grind lines were blurred out, and the edge bevel showed frequent large irregularities where corrosion had removed significant amounts of metal (~10x greater than the micro teeth left by the DMT rod).
Repeating the sharpness testing :
D2 -> 1.31 +/- 0.18 cm
VG -> 1.20 +/- 0.10
A8 -> 1.13 +/- 0.19
The D2 one shows the greatest increase but it is too small to say definitely that it isn't just a random increase. In retrospect this would have been a good occasion to use thread or as Jeff suggest ribbon cutting as it would have been more sensitive to the blunting than the poly which could actually be enhanced by edge corrosion as it can actually enhance the saw like effect of coarse edges. However since such edges contain iron oxide which is very weak, they are prone to excessive blunting in use.
To examine how the blades edges wore, the knives were used to cut sixteen pieces of 3/8" hemp with a two inch draw. The D2 knife felt very different on the rope, it acted more aggressive, but was much harder to pull through the rope (this would have been a good time to measure the force I was using on the hemp as it was obviously larger with the D2 blade). The blades were then again tested for sharpness :
D2 -> 2.30 +/- 0.24 cm
VG -> 1.66 +/- 0.17
A8 -> 1.70 +/- 0.28
If you compare this to how the blades had done in the last bout of rope cutting after a similar amount of cuts [no corrosion factor in that rope cutting], the results are not significantly different for the VG-10 and AUS-8A blades. Those results :
D2 -> 1.30 +/- 0.08 cm
VG -> 1.35 +/- 0.09
A8 -> 1.55 +/- 0.15
Thus the VG-10 and AUS-8A blade were not significantly effected by the lemon juice and performed very similar as if they had not been exposed. However there was a huge difference in the D2 performance. It wore down much faster in use after being exposed to lemon juice. It was now blunting the fastest out of all three steels.
It would be interesting to repeated the hemp rope cutting trials completely, with exposing the blades in salt water during the cuts. How does blunting correlate to the soak time? If you just dipped the blades in while doing the cutting would rust ever have a chance to form [probably not as Cougar frequently points out]?
Ref :
http://www.bladeforums.com/forums/showthread.php?s=&threadid=236308
http://www.bladeforums.com/forums/showthread.php?s=&threadid=241331
-Cliff
Sharpness before the soaking, as measured on 1/4" poly (length of blade needed to cut the cord) :
D2 -> 1.10 +/- 0.16 cm
VG -> 1.14 +/- 0.22
A8 -> 1.10 +/- 0.09
All blades have equally sharp edges at the start. The knives were sharpened using a DMT 600 grit rod set at 22 degrees. After a two hour soak the AUS-8A (A8) and VG-10 blade looked no different, no sign of corrosion by eye or under magnification. The edge bevel grinds lines were still clear under the scope. The D2 blade however had a distinct patina in all the contact area and parts of the edge bevel were solid black with oxidation (~one cm lengths). Checking the edge under magnification on the D2 knife, the grind lines were blurred out, and the edge bevel showed frequent large irregularities where corrosion had removed significant amounts of metal (~10x greater than the micro teeth left by the DMT rod).
Repeating the sharpness testing :
D2 -> 1.31 +/- 0.18 cm
VG -> 1.20 +/- 0.10
A8 -> 1.13 +/- 0.19
The D2 one shows the greatest increase but it is too small to say definitely that it isn't just a random increase. In retrospect this would have been a good occasion to use thread or as Jeff suggest ribbon cutting as it would have been more sensitive to the blunting than the poly which could actually be enhanced by edge corrosion as it can actually enhance the saw like effect of coarse edges. However since such edges contain iron oxide which is very weak, they are prone to excessive blunting in use.
To examine how the blades edges wore, the knives were used to cut sixteen pieces of 3/8" hemp with a two inch draw. The D2 knife felt very different on the rope, it acted more aggressive, but was much harder to pull through the rope (this would have been a good time to measure the force I was using on the hemp as it was obviously larger with the D2 blade). The blades were then again tested for sharpness :
D2 -> 2.30 +/- 0.24 cm
VG -> 1.66 +/- 0.17
A8 -> 1.70 +/- 0.28
If you compare this to how the blades had done in the last bout of rope cutting after a similar amount of cuts [no corrosion factor in that rope cutting], the results are not significantly different for the VG-10 and AUS-8A blades. Those results :
D2 -> 1.30 +/- 0.08 cm
VG -> 1.35 +/- 0.09
A8 -> 1.55 +/- 0.15
Thus the VG-10 and AUS-8A blade were not significantly effected by the lemon juice and performed very similar as if they had not been exposed. However there was a huge difference in the D2 performance. It wore down much faster in use after being exposed to lemon juice. It was now blunting the fastest out of all three steels.
It would be interesting to repeated the hemp rope cutting trials completely, with exposing the blades in salt water during the cuts. How does blunting correlate to the soak time? If you just dipped the blades in while doing the cutting would rust ever have a chance to form [probably not as Cougar frequently points out]?
Ref :
http://www.bladeforums.com/forums/showthread.php?s=&threadid=236308
http://www.bladeforums.com/forums/showthread.php?s=&threadid=241331
-Cliff