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- Jul 30, 2006
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Howdy
Dennis Strickland has an amazing collection of cutlery. Whether it be the nicest GEC traditional or the latest hot alloy, Dennis probably has it. He also has the knowledge base to go with it, as hes been collecting and using knives for a long time (longer than I, and Ive been using knives for ~50 years). Dennis and I occasionally discuss blades and steel via PM. Recently, Dennis asked me if I would like to try some high-end PM steels. Now obviously, since I never met a steel alloy I didnt like, I said, Yes, please.
Without further ado, Dennis sent me 3 exotic PM steel blades to try: ZDP-189, M390, and CPM M4 HC. I added in my own S30V just for the fun of it.
Test Method:
If youve read my testing posts, you know my methods, Watson.
http://www.bladeforums.com/forums/showthread.php?t=641279
http://www.bladeforums.com/forums/showthread.php?t=743238
http://www.bladeforums.com/forums/showthread.php?t=769447
If youre you are familiar with the test method, skip down to the steel section. (You can do this anyway but if you arent familiar with my test method, my results will make more sense to you if you read the next couple of paragraphs.)
There are a number of factors that enter in to blade performance, several of which have more impact on edge retention than blade alloy does.
- Blade geometry
- Edge Angle
- alloy composition
- Alloy hardness.
I try to control as many as possible.
- I measure the hardness of each blade. (I cant control the hardness, but it helps me understand what I am testing and helps me reach conclusions.)
- I modify the edge angles so that they are all the same (15° per side)
- I do my best to put an equally sharp edge on each blade. In this set of tests I used DMT diamond stones, X-tra Coarse, Coarse, Fine, X-tra Fine.
- I make an equal number of cuts through 3/8 manila rope with each blade. I usually mark out on the blade my intended start and stop so that I use approximately the same length of blade on each knife. In this comparison, I used ~2 of each blade.
- I do my cutting on a simple jig that supports the rope, but has a split in it so that the blade only cuts rope. That way the blade does not hit the support. This makes the forces acting on the blade more uniform and the results much more reproducible. I try very hard to cut at 90° to the rope.
- I then examine the edges under a 3x lens using a high intensity lamp looking for light reflected off the edge of the blade. The shiny spots equate to wear or deformation. I always check the blades before beginning the rope cutting to make sure I can see no edge at all under the lens in the light.
- I rank the blades by the amount of deformation I observe.
- I repeat the tests several times until I am sure of the results.
The advantage to this method is that the blade geometry is not a factor in the results. This allows me to eliminate a major factor in cutting performance.
The disadvantage is that it is a comparative method. It is extremely difficult to quantify the difference and say that one blade is 25% better than another. For the most part one can only rank the alloys and say that one is better than another.
The knives:
Blade Alloy____Measured Hardness ____Maker_______Model
CPM M4 HC______62 _______________Spyderco ___Gayle Bradely
ZDP-189________62 _______________Spyderco____Stretch II
M390___________60.5______________Benchmade__710
S30V___________59.6 ______________Buck_______Vantage-Pro
Here are data sheets on the alloys, (note that the Gayle Bradley uses CPM M4 HC, which does not have exactly the same composition as melt M4).
http://www.crucibleservice.com/PDFs/\DataSheets2010\dsM4v1 2010.pdf
http://www.crucibleservice.com/PDFs/\DataSheets2010\dsS30Vv1 2010.pdf
http://www.bohler-edelstahl.com/files/M390DE.pdf
No gots for ZDP-189.
It is probably worth noting that none of these knives was heat treated to maximize edge retention. These are all standard working blades. Each has a heat treat that will provide a measure of toughness in addition to edge retention. The Crucible data sheet says you can take CPM M4 HC to a 65.5 and the Bohler data sheet says you can get M390 to almost 63. So take that into consideration when you look at my information. The results may change somewhat if the heat treats were different.
Results and discussion:
In order of retension, best at the top:
CPM M4 HC M390
ZDP-189
S30V.
I could not differentiate between M390 and CPM M4 HC. After some runs, I thought maybe the CPM M4 was less damaged, after others, I thought the M390 had fared better. Bottom line: a tie.
What I really found significant in this comparison was the relative edge retentions of M390 and CPM M4 HC compared to those of other alloys I have tested. When testing 440C and VG10 by this method, I found that I saw enough damage to rank the alloys after ~20 cuts. To see that level of damage on ZDP-189 in this test, I had to go to 40 cuts. To see that level of damage with either M390 or ZDP-189 I had to go to 80 cuts. Now all those alloys were still easily cutting the rope after that many cuts, but that is about how many it took for me to be able to discern damage to the edge. Based on this, I made a graph to show relative edge retentions of theses alloys in comparison to some other, more common alloys:
One thing that fascinates me about this comparison is that, for a long time it's been clear that edge geometry is more important than alloy. I'm not sure if that is still clear to me. I can't help wondering if a blunter blade of M390 might not outcut a blade with better geometry, but lesser alloy. A battle for another day, I think
Thanks to Dennis for loaning the knives. I learned a lot from this comparison. I hope others find it useful, as well.
Frank R
Dennis Strickland has an amazing collection of cutlery. Whether it be the nicest GEC traditional or the latest hot alloy, Dennis probably has it. He also has the knowledge base to go with it, as hes been collecting and using knives for a long time (longer than I, and Ive been using knives for ~50 years). Dennis and I occasionally discuss blades and steel via PM. Recently, Dennis asked me if I would like to try some high-end PM steels. Now obviously, since I never met a steel alloy I didnt like, I said, Yes, please.
Without further ado, Dennis sent me 3 exotic PM steel blades to try: ZDP-189, M390, and CPM M4 HC. I added in my own S30V just for the fun of it.
Test Method:
If youve read my testing posts, you know my methods, Watson.
http://www.bladeforums.com/forums/showthread.php?t=641279
http://www.bladeforums.com/forums/showthread.php?t=743238
http://www.bladeforums.com/forums/showthread.php?t=769447
If youre you are familiar with the test method, skip down to the steel section. (You can do this anyway but if you arent familiar with my test method, my results will make more sense to you if you read the next couple of paragraphs.)
There are a number of factors that enter in to blade performance, several of which have more impact on edge retention than blade alloy does.
- Blade geometry
- Edge Angle
- alloy composition
- Alloy hardness.
I try to control as many as possible.
- I measure the hardness of each blade. (I cant control the hardness, but it helps me understand what I am testing and helps me reach conclusions.)
- I modify the edge angles so that they are all the same (15° per side)
- I do my best to put an equally sharp edge on each blade. In this set of tests I used DMT diamond stones, X-tra Coarse, Coarse, Fine, X-tra Fine.
- I make an equal number of cuts through 3/8 manila rope with each blade. I usually mark out on the blade my intended start and stop so that I use approximately the same length of blade on each knife. In this comparison, I used ~2 of each blade.
- I do my cutting on a simple jig that supports the rope, but has a split in it so that the blade only cuts rope. That way the blade does not hit the support. This makes the forces acting on the blade more uniform and the results much more reproducible. I try very hard to cut at 90° to the rope.
- I then examine the edges under a 3x lens using a high intensity lamp looking for light reflected off the edge of the blade. The shiny spots equate to wear or deformation. I always check the blades before beginning the rope cutting to make sure I can see no edge at all under the lens in the light.
- I rank the blades by the amount of deformation I observe.
- I repeat the tests several times until I am sure of the results.
The advantage to this method is that the blade geometry is not a factor in the results. This allows me to eliminate a major factor in cutting performance.
The disadvantage is that it is a comparative method. It is extremely difficult to quantify the difference and say that one blade is 25% better than another. For the most part one can only rank the alloys and say that one is better than another.
The knives:
Blade Alloy____Measured Hardness ____Maker_______Model
CPM M4 HC______62 _______________Spyderco ___Gayle Bradely
ZDP-189________62 _______________Spyderco____Stretch II
M390___________60.5______________Benchmade__710
S30V___________59.6 ______________Buck_______Vantage-Pro
Here are data sheets on the alloys, (note that the Gayle Bradley uses CPM M4 HC, which does not have exactly the same composition as melt M4).
http://www.crucibleservice.com/PDFs/\DataSheets2010\dsM4v1 2010.pdf
http://www.crucibleservice.com/PDFs/\DataSheets2010\dsS30Vv1 2010.pdf
http://www.bohler-edelstahl.com/files/M390DE.pdf
No gots for ZDP-189.
It is probably worth noting that none of these knives was heat treated to maximize edge retention. These are all standard working blades. Each has a heat treat that will provide a measure of toughness in addition to edge retention. The Crucible data sheet says you can take CPM M4 HC to a 65.5 and the Bohler data sheet says you can get M390 to almost 63. So take that into consideration when you look at my information. The results may change somewhat if the heat treats were different.
Results and discussion:
In order of retension, best at the top:
CPM M4 HC M390
ZDP-189
S30V.
I could not differentiate between M390 and CPM M4 HC. After some runs, I thought maybe the CPM M4 was less damaged, after others, I thought the M390 had fared better. Bottom line: a tie.
What I really found significant in this comparison was the relative edge retentions of M390 and CPM M4 HC compared to those of other alloys I have tested. When testing 440C and VG10 by this method, I found that I saw enough damage to rank the alloys after ~20 cuts. To see that level of damage on ZDP-189 in this test, I had to go to 40 cuts. To see that level of damage with either M390 or ZDP-189 I had to go to 80 cuts. Now all those alloys were still easily cutting the rope after that many cuts, but that is about how many it took for me to be able to discern damage to the edge. Based on this, I made a graph to show relative edge retentions of theses alloys in comparison to some other, more common alloys:
One thing that fascinates me about this comparison is that, for a long time it's been clear that edge geometry is more important than alloy. I'm not sure if that is still clear to me. I can't help wondering if a blunter blade of M390 might not outcut a blade with better geometry, but lesser alloy. A battle for another day, I think
Thanks to Dennis for loaning the knives. I learned a lot from this comparison. I hope others find it useful, as well.
Frank R