Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Awhile ago I posted up some work done with three Deerhunters from A.G. Russell, cutting up lots of cardboard with AUS-8A (57-59 RC), VG-10 (59-61 RC) and D2 (59-61 RC)versions of the knife. Ref :
http://www.bladeforums.com/forums/showthread.php?s=&threadid=236308
I finally finished off a more quantitative comparison on 3/8" hemp. The rope was cut with a two inch draw, the sharpness tested periodically using quarter inch poly. The poly was held under 1000 g of tension and cut on a draw, the blade length needed to make a cut was taken as a measure of the sharpness. The amount of force needed to cut the hemp was also noted, but it is a much more coarse measurement of sharpness as it depends strongly on the geometry. The cutting was done three times for each blade with 254 cuts for each blade in each round, 2286 cuts in all [~60 000 lbs of force applied total, better eat your wheaties].
The blades were sharpened before each round, starting with a profiling using SiC sandpaper to set the bevels, working up to 400 grit. The final sharpening was on a 600 grit DMT rod set at 22 degrees [simply because I have a cheap stand at that angle]. The edges were formed with 15 strokes per side (alternating) to insure that the edge was fully composed of the 600 finish [only about 5 per side are really necessary]. The edge was stropped on white non abrasive paste to clean up the grit and steel debris. All edges were checked under magnification for uniformity of finish.
The results :
http://www.physics.mun.ca/~sstamp/images/edge_retention_deerhunters.gif
The VG-10 blade is ahead of the AUS-8 one by about 50% meaning that it takes 50% more material to induce a similar amount of blunting. The D2 one is again ahead, by about 100% over the VG-10 one. The difference here is great enough that you can feel a large difference in the cutting, it remains more aggressive on the rope for far longer.
Getting a bit more technical with the numbers and fitting the results to a few simply numerical models, you could look at edge retention in a number of ways, cuts to achive a certain level of blunting (percentage of initial sharpness for example), or performance after a certain number of cuts. The same ranking would take place for both perspectives, but the distances between the ranks would be far greater for the first method.
To be optimal, a number of blades of each type should be tested, three of each for example taking one round each instead of running three trials on the same blade, as well RC tests should be done . In the above for example, was the greater edge retention of the D2 blade as compared to the VG-10 one because of the wear resistance advantage of D2 or a possible 61 RC D2 blade tested against a 59 RC VG-10 one. Only the shadow knows.
Ref :
http://www.agrknives.com/agrussell/agdh-8a.html
[the numbers behind the graph were posted to usenet, you can also email if you are interested in the details]
-Cliff
http://www.bladeforums.com/forums/showthread.php?s=&threadid=236308
I finally finished off a more quantitative comparison on 3/8" hemp. The rope was cut with a two inch draw, the sharpness tested periodically using quarter inch poly. The poly was held under 1000 g of tension and cut on a draw, the blade length needed to make a cut was taken as a measure of the sharpness. The amount of force needed to cut the hemp was also noted, but it is a much more coarse measurement of sharpness as it depends strongly on the geometry. The cutting was done three times for each blade with 254 cuts for each blade in each round, 2286 cuts in all [~60 000 lbs of force applied total, better eat your wheaties].
The blades were sharpened before each round, starting with a profiling using SiC sandpaper to set the bevels, working up to 400 grit. The final sharpening was on a 600 grit DMT rod set at 22 degrees [simply because I have a cheap stand at that angle]. The edges were formed with 15 strokes per side (alternating) to insure that the edge was fully composed of the 600 finish [only about 5 per side are really necessary]. The edge was stropped on white non abrasive paste to clean up the grit and steel debris. All edges were checked under magnification for uniformity of finish.
The results :
http://www.physics.mun.ca/~sstamp/images/edge_retention_deerhunters.gif
The VG-10 blade is ahead of the AUS-8 one by about 50% meaning that it takes 50% more material to induce a similar amount of blunting. The D2 one is again ahead, by about 100% over the VG-10 one. The difference here is great enough that you can feel a large difference in the cutting, it remains more aggressive on the rope for far longer.
Getting a bit more technical with the numbers and fitting the results to a few simply numerical models, you could look at edge retention in a number of ways, cuts to achive a certain level of blunting (percentage of initial sharpness for example), or performance after a certain number of cuts. The same ranking would take place for both perspectives, but the distances between the ranks would be far greater for the first method.
To be optimal, a number of blades of each type should be tested, three of each for example taking one round each instead of running three trials on the same blade, as well RC tests should be done . In the above for example, was the greater edge retention of the D2 blade as compared to the VG-10 one because of the wear resistance advantage of D2 or a possible 61 RC D2 blade tested against a 59 RC VG-10 one. Only the shadow knows.
Ref :
http://www.agrknives.com/agrussell/agdh-8a.html
[the numbers behind the graph were posted to usenet, you can also email if you are interested in the details]
-Cliff
