Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
I intended this to be a simple test, cut cardboard until it became too difficult with each blade. Then look at each blade under a couple of sharpness tests to evaluate just how much of a difference in blunting was induced, and a few sharpening methods to see how the blades responded. In theory it seemed sound, but in practice it didn't go as planned.
I was cutting 1/4" double line-ridged cardboard, through the ridges using the entire blade length on a slicing pass. This was the critical mistake. Slicing is a very poor way in general to test for sharpness as it "smears" the cut out so much that blunt spots can be hidden, and in general a blade can be far blunter and still slice something that what is required to do a push cut. In retrospect the cutting should have been done with a push cut, and all cuts done on a very small area of the blade. This would have also allowed a quick and easy comparison of before and after sharpness as much of the blade would still be at full sharpness.
The result : each blade cut all the cardboard at hand, ~600 feet total. I could not tell the blades apart by feel in use. I then did some cuts measuring the amount of force required. The blades would cut into the cardboard with less than a pound of force, however to push the blades through the cardboard required ~25 lbs. Thus the effect that sharpness had on the cutting ability was very small. For example if the AUS-8A blade had degraded twice as much as the other knives, the total effect on the force increase would be just ~4 percent. Thus in other words it was impossible to judge the sharpness of the blades by the amount of force of the cuts.
Inspecting the blades under magnification revealed another side to the picture. The AUS 8A blade had much more extensive wear, it was missing pieces of blade about twice as deep as the other steels [2.5 mm chips, with patches of wear up to 1 cm long [x20 mag]) and as much or more in total amount of wear. Thus there was no doubt that the AUS-8A blade blunted much more than the others, which isn't surprising. The VG-10 and D2 blade were very close, it would be difficult to judge which was more worn, but the D2 blade would probably be given the nod.
I then stropped each blade, five passes per side on CrO. The AUS-8 blade jumped back immediately back to hair shaving ability and was now sharper than the other two. Under magnification though the more extensive edge damage was still there, the edge had just been more responsive to the aligned and light polish of the very edge. However when the edges were restored fully using SiC sandpaper, the AUS-8A blade took about three times as long to have all the damage removed. This is a rough estimate as I was only checking even 10 passes, this was all that was required for the VG-10 and D2 blade, but the AUS-8A one took two more runs of 10 passes.
No real surprises in the above, the harder and more wear resistant blades take less blunting in the cutting and take less effort to restore on an abrasive as the damage isn't as extensive. The softer blade is however more responsive to the stropping. Geometry is also shown to be much more key in determing the cutting ability of a knife when cutting thick and binding materials than the actual sharpness of the edge.
-Cliff
I was cutting 1/4" double line-ridged cardboard, through the ridges using the entire blade length on a slicing pass. This was the critical mistake. Slicing is a very poor way in general to test for sharpness as it "smears" the cut out so much that blunt spots can be hidden, and in general a blade can be far blunter and still slice something that what is required to do a push cut. In retrospect the cutting should have been done with a push cut, and all cuts done on a very small area of the blade. This would have also allowed a quick and easy comparison of before and after sharpness as much of the blade would still be at full sharpness.
The result : each blade cut all the cardboard at hand, ~600 feet total. I could not tell the blades apart by feel in use. I then did some cuts measuring the amount of force required. The blades would cut into the cardboard with less than a pound of force, however to push the blades through the cardboard required ~25 lbs. Thus the effect that sharpness had on the cutting ability was very small. For example if the AUS-8A blade had degraded twice as much as the other knives, the total effect on the force increase would be just ~4 percent. Thus in other words it was impossible to judge the sharpness of the blades by the amount of force of the cuts.
Inspecting the blades under magnification revealed another side to the picture. The AUS 8A blade had much more extensive wear, it was missing pieces of blade about twice as deep as the other steels [2.5 mm chips, with patches of wear up to 1 cm long [x20 mag]) and as much or more in total amount of wear. Thus there was no doubt that the AUS-8A blade blunted much more than the others, which isn't surprising. The VG-10 and D2 blade were very close, it would be difficult to judge which was more worn, but the D2 blade would probably be given the nod.
I then stropped each blade, five passes per side on CrO. The AUS-8 blade jumped back immediately back to hair shaving ability and was now sharper than the other two. Under magnification though the more extensive edge damage was still there, the edge had just been more responsive to the aligned and light polish of the very edge. However when the edges were restored fully using SiC sandpaper, the AUS-8A blade took about three times as long to have all the damage removed. This is a rough estimate as I was only checking even 10 passes, this was all that was required for the VG-10 and D2 blade, but the AUS-8A one took two more runs of 10 passes.
No real surprises in the above, the harder and more wear resistant blades take less blunting in the cutting and take less effort to restore on an abrasive as the damage isn't as extensive. The softer blade is however more responsive to the stropping. Geometry is also shown to be much more key in determing the cutting ability of a knife when cutting thick and binding materials than the actual sharpness of the edge.
-Cliff
