Monofletch
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If Scotchbright is so abrasive--can it be used to sharpen or strop a good edge?
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Scotch-Brite test for blade quality
- Thread starter Rüdemann
- Start date
Hot damm! I bought an M2 from a knife maker in New York. Sharp as hell, but it's too short for anything but a "dress" knife - you know, when you wear a knife every day it's hard to go out without one, but the really useful ones are too big for "dress" and hang down too far. It embarrasses all your posh friends. I might mention that I "outgrew" or changed my mind about knives. I gave up all folders in favor of fixed blades; they're ready to go, and ostensibly tougher - straight piece of steel vs a folding mechanism. Well, I didn't give up folders completely; I keep a SAK "Classic" in my pocket - tiny blade, little screwdriver blade, toothpick, tweezers and tiny scissors - bess all around useful knife they is - excellent for cuttin strings offun uniforms (27 years), pickin your teef an tweezin splinters, not to mention sharpenin your carpenters pencil.
I'm no expert, but it might work best on convex blades - where you sharpen "backwards", and the pad has the "give" required for the convex blades. The surface of the Stotch-Brite seems too "rough" to draw a knife forward - like a standard flat grind or hollow ground knife.
You're right about the testing. The way I see it, the only accurate way to test the edge-holding capabilities of various steels is to have identical knives/blades made of different steels, same exact blade shape and profile, same exact edge geometry, precisely identical levels of sharpness, carefully record the hardness of the blade edges, use an identical test medium for each blade, and cut each piece of test medium the exact same way with each blade. I figure that's about as scientific a test one could perform without high-tech equipment. But even the testing I've described is open to human error and the results subject to unintentional influence.
Testing different blades made of different steels with different blade/edge geometries and different levels of hardness won't produce any meaningful test results. But everyone has their own idea of fun.
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Scotch brite is used to create a Scotch brite finish, strangely enough. After the steel is hardened (to avoid quench cracks on a rough surface) the hardened steel is abraded by the Scotch brite to produce a finish of fine linear scratches. You could probably sharpen the edge with the same belt/disc, the aluminum oxide is used in India stones, waterstones, and sandpaper.
Rüdemann;11178436 said:
The beauty of fully hardened M2 is that it has both very high wear resistance and very high hardness. The batch of blades my supply came from was tested to be between 64.5 and 66 HRc. At that hardness, it also flexed 90 degrees 10 times without any cracking or set in the blade, and I was able to dig a hole through a 1x8 without tip damage. Of course all that is dominated by geometry, but you get the idea. Unless you know for sure, I'd be skeptical of any commercial blade being that high in hardness. That blade was a real winner. It would come straight off the leather power strop on the belt sander and tree top hair 1/4" above my skin. Also, surprisingly easy to sharpen on hand stones as well. I've seen nothing like it since. Got some A2 to pick up later this week that's between 61 and 63 HRc, so maybe it will be close. I like hard steel. Anything below 60 to me is a waste of effort if the steel has the carbon to do it.
With homage to the sage advice of hardheart and Killgar, et. al, below are the test results: The parameters of the Website seem to not allow for the upload of an Excel spreadsheet so I will just enter the information and hope the formatting holds.
a. All knives were (previously) sharpened with two bevels (18 and 23 degrees).
b. Blade geometry is NOT consistent - some flat grinds, some hollow ground, modified flat grind.
c. All cuts were made through the sponge side into the Scotch-Brite side.
d. Each "cut" cut a slice from the pad/sponge.
e. All blades had been finished on a very fine stone, probably a mistake for this test, but they had already been sharpened and didn't want to re-sharpen for this test.
f. Modified Flat Grind: I'm not an expert in blade design so what I am calling a modified flat grind is a flat ground blade that the manufacturer made a single pass on both sides of the blade on the grinding wheel toward making a hollow ground blade and stopped. The blade maintains maximum thickness anywhere from the top half to the top 2/3rds, depending on the manufacturer. The pros here can help with the name for this kind of grind.
g. Blade thickness was measured at the spine.
Results of my Scotch-Brite pad/sponge test of edge retention on blades of various geometry and steels:
1. Blackbird SK-5 - Flat Grind - 1/8" thick - 154CM - Second cut showed signs of edge loss. Third cut was a struggle.
2. Busse Team Gemini - Flat Grind - 1/4" thick - INFI - Could barely get through the second cut.
3. WWII Cattaraugus 225-Q - Modified Flat Grind - +1/8" thick (4mm) - 1095 Carbon (?) - Could barely get through the second cut.
4. Frost Cutlery - Hollow Ground - 1/8" thick - 420 (?) - Struggled through the first cut.
5. Hen & Rooster (Toledo, Spain) - Hollow Ground - 1/8" thick - ? stainless - Second cut showed signs of edge loss. Third cut was a struggle.
6. Knives of Alaska - Hollow Ground - +1/8" thick (4mm) - S30V - Second cut showed signs of edge loss. Third cut was a struggle.
7. Ontario RAT-7 - Flat Grind - 3/16" thick - D-2 - Second cut showed signs of edge loss. Third cut was a struggle.
8. Swedish Puukko - Modified Flat Grind - -(under) 1/8" thick (3mm) - ? stainless - could barely get through the second cut.
9. Western R-16 - Hollow Ground - -(under) 1/8" thick (3mm) - 420 ? - Second cut showed signs of edge loss. Third cut was a struggle.
10. W.R. Case Ridgeback - Hollow Ground - -(under) 1/8" thick (3.5mm) - "surgical stainless" - Second cut showed signs of edge loss. Third cut was a struggle.
Conclusions:
1. Mostly the hollow ground blades did better; probably because they were thinner (slicer-like) on the lower half of the blade. However, the Ontario RAT-7 (D-2) & SK-5 (154 CM) gave the same results as the hollow ground blades and it is a completely flat ground blade. As noted, blade geometry was not consistent so the results have only a notch or two above irrelevant.
2. As foretold, the Scotch-Brite medium killed all the edges - quickly. So, if you need a handy size of Scotch-Brite cut it with scissors before you go camping. Or, take a sharpening stone with you.
3. I am reminded of some old movie where a broadsword was great at hacking, but the katana sword sliced through a silk scarf thrown in the air like butter. Neither could match the other's strengths, but the strengths were different.
a. All knives were (previously) sharpened with two bevels (18 and 23 degrees).
b. Blade geometry is NOT consistent - some flat grinds, some hollow ground, modified flat grind.
c. All cuts were made through the sponge side into the Scotch-Brite side.
d. Each "cut" cut a slice from the pad/sponge.
e. All blades had been finished on a very fine stone, probably a mistake for this test, but they had already been sharpened and didn't want to re-sharpen for this test.
f. Modified Flat Grind: I'm not an expert in blade design so what I am calling a modified flat grind is a flat ground blade that the manufacturer made a single pass on both sides of the blade on the grinding wheel toward making a hollow ground blade and stopped. The blade maintains maximum thickness anywhere from the top half to the top 2/3rds, depending on the manufacturer. The pros here can help with the name for this kind of grind.
g. Blade thickness was measured at the spine.
Results of my Scotch-Brite pad/sponge test of edge retention on blades of various geometry and steels:
1. Blackbird SK-5 - Flat Grind - 1/8" thick - 154CM - Second cut showed signs of edge loss. Third cut was a struggle.
2. Busse Team Gemini - Flat Grind - 1/4" thick - INFI - Could barely get through the second cut.
3. WWII Cattaraugus 225-Q - Modified Flat Grind - +1/8" thick (4mm) - 1095 Carbon (?) - Could barely get through the second cut.
4. Frost Cutlery - Hollow Ground - 1/8" thick - 420 (?) - Struggled through the first cut.
5. Hen & Rooster (Toledo, Spain) - Hollow Ground - 1/8" thick - ? stainless - Second cut showed signs of edge loss. Third cut was a struggle.
6. Knives of Alaska - Hollow Ground - +1/8" thick (4mm) - S30V - Second cut showed signs of edge loss. Third cut was a struggle.
7. Ontario RAT-7 - Flat Grind - 3/16" thick - D-2 - Second cut showed signs of edge loss. Third cut was a struggle.
8. Swedish Puukko - Modified Flat Grind - -(under) 1/8" thick (3mm) - ? stainless - could barely get through the second cut.
9. Western R-16 - Hollow Ground - -(under) 1/8" thick (3mm) - 420 ? - Second cut showed signs of edge loss. Third cut was a struggle.
10. W.R. Case Ridgeback - Hollow Ground - -(under) 1/8" thick (3.5mm) - "surgical stainless" - Second cut showed signs of edge loss. Third cut was a struggle.
Conclusions:
1. Mostly the hollow ground blades did better; probably because they were thinner (slicer-like) on the lower half of the blade. However, the Ontario RAT-7 (D-2) & SK-5 (154 CM) gave the same results as the hollow ground blades and it is a completely flat ground blade. As noted, blade geometry was not consistent so the results have only a notch or two above irrelevant.
2. As foretold, the Scotch-Brite medium killed all the edges - quickly. So, if you need a handy size of Scotch-Brite cut it with scissors before you go camping. Or, take a sharpening stone with you.
3. I am reminded of some old movie where a broadsword was great at hacking, but the katana sword sliced through a silk scarf thrown in the air like butter. Neither could match the other's strengths, but the strengths were different.
No. It's not smooth enough. But alu oxide sandpaper, which is the same absrasive in a less fluffy form, is a greater sharpening tool.
Another way to say the above is that the Scotch Brite is too soft and will wrap around the edge (destroying it) when the bevel is pressed into it to make contact. Also, the abrasive grains in SB are all through the nylon matrix, making it a 3-dimensional abrasive, unlike sandpaper where the grit particless are all on one plane.
I think I got it now, meanwhile. Also, I knew before I did the test that Scotch-Brite was abrasive - thanks to several members here. And, I knew before this that one shouldn't use a sword to remove a splinter - many knives are purpose-built. On the other hand, as with most things in life, everything is easy when you know the answers; learning the answers is the hard part. Apparently, even metallurgists have not figured out how to make the perfect multipurpose blade since they keep coming up with the next iteration of "super" steel.
Is there a real purpose for Me2 to drill a hole in a piece of 1x8 with his M2 blade when everybody knows a drill would do a much better job? Folks who love knives are probably always looking for THE knife. Kinda like anybody and everybody can be a suicide bomber - once. My little test seems to indicate that almost any knife can cut Scotch-Brite - once. You can spend $10. or $300. and you cut Scotch-Brite - once. There is even a steel or style of knife that can do it twice; maybe three times. Yes, scissors are better at it, and so is a drill for drilling holes and a saw for cutting wood. My search is for the best all around knife. Maybe this knife is made of unobtanium, but I think a lot of knife lovers are looking for the perfect blade. Purists would ask: "perfect blade for what purpose?" We regular folk would answer: "everything".
People here offered that all those "destructive" "survivalist" tests are meaningless or senseless or silly because you don't need a knife to do this stuff in your everyday life. Likewise, 2WD can do almost anything a 4WD can do - in most peoples' everyday life. Cars weren't built to be stuck in snow or mud, but the guy with 4WD or AWD got his money's worth the first time he needed it.
Thirty years ago, if you asked for a knife that could withstand cutting car steel AND bend 30 or so degrees from perpendicular AND stay sharp you'd be labeled a kook. Now there are steels that can do this - more than once. Some would still label you a kook for wanting such a knife because "nobody" needs a knife like this in their daily lives. Considered more broadly, knives that can perform these extreme tasks can still cut your string, rope, cardboard and packing tape. They are way more expensive than an old Imperial which is suitable for mundane tasks, but not up to the challenge of newer steels.
Why are Randall knives so expensive? Is it the steel? Is it the grind? Is it the hype? Are any but a select few ever going to find out if a Randall can dig a fire hole or baton through wood, cut kindling, etc. and stay sharp? So, the real question is, are the expensive steels worth the money? Is INFI steel any better than AUS-8, AUS-10, D-2, 154CFM, S30V, S40-60-90V, M2, A-1,etc. Again, the purist would ask: "for what purpose", and again we regular folk, who don't know any better would answer: "for every purpose" - gut deer, moose, (pound through bone [yes an axe would be better]) make a shelter, dig a fire hole, cut kindling, make a spear, remove a tire from it's rim, cut cardboard, string, rope (2" rope in one swipe), bailing twine, and on. Do we need a knife like this everyday, no!
As with 4WD, spare tires or condoms, you don't need it till you need it. Or, otherwise stated: It is better to have it and not need it than to need it and not have it. I think that is why somebody decided to make Multi-tools like Leathermans. Sure a real screwdriver would work better, and a real file would work better, etc., but you can't or won't carry all the "perfect" tools for the job. So, maybe there is no perfect knife, but according to these "survivalist" tests, there are some knives getting close. The hard part is trying to figure out if a $100. Ontario (D-2 or 1095) will do absolutely everything a Cold Steel San Mai III Trailmaster can do without spending the money to find out. Am I going to thrust my my Busse Team Gemini sideways into a tree, haul myself up and stand on the knife? Not unless a big ole bear or mountain lion is chasin me. However, that is what James Morgan Ayres does to the knives he tests, and it is somehow comforting to know that I can buy a knife that will do this even if I don't need a knife to do this as I go about my daily life; I might tomorrow.
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Rüdemann;11181992 said:
Admirable empiricism - really nice to see. But some other things to know
1. The results you got were specific to that material - which is rather overload for any knife steel and will have squashed variations you'd see with many other materials
2. Steels can diverge hugely in their time to reach utter bluntness, but take almost the same time to reach the point where any sane person would re-sharpen them
3. Geometry will have a considerable effect on perceived sharpness cutting an abrasive by physically weak material
#2 is the big one; marketers often claim "X45 has 4 times the edge retention of 440A" and this is true if you're measuring the time taken to reach 90% bluntness. But they make take virtually the same time to reach 20% bluntness (ie the point when you have to use a 20% longer cut to sever the same width of material.) In fact, this is very often the case - for people with the sense and opportunity to touch up their blades for a few seconds now and then, edge retention is much more of a muchness with different steels.
If you're into this type of thing, you might want to look at Cliff Stamp's form and knifetests.com
Really good example:
http://jeffpeachey.wordpress.com/tag/tool-steel-cutting-edge-retention/
Note that the knife with the cooler looking graph costs vastly more, is a huge pain to re-sharpen, and when you look at the early part of the graph where most sharpness is lost - but which the eye tends to ignore because it is a small part of the whole - performs little better than the other knives.
Thank you meanwhile for your gracious help and advice, and I am appreciative to others here who imparted their wisdom to me in trying to sift through all the fantastic claims of fantastic knives at fantastic prices.
Also: wear resistance - which is what your test possibly measures - often doesn't alter edge retention. WR kicks in when a blade has to keep contact thwith cut material as it pushes through it. So they're often quoted separately, eg
http://www.bladeforums.com/forums/s...ss-Steel-Chart-Comparison-for-EDC-Knives-v4-0
http://www.bladeforums.com/forums/s...ss-Steel-Chart-Comparison-for-EDC-Knives-v4-0
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Interesting link. I personally do not at all care for the bluntness comparison, because then you rely on the initial sharpness. If the blade is not very sharp to begin with, then reading 20 or 90 or any percentage of sharpness is going to be skewed. So then which is better, and which is the better comparison for real world application? For example, one of the blades I had tested cut 161.6 mm on the first 3 strokes, 1007.1 mm after 60 strokes, but only cut 3.3 mm on the last stroke, using the same CATRA protocol. So it cut more initially, and cut more in total at the end of the test, but the T15 blade was cutting 3 times as much per stroke at the end of the test. So which is more valuable? Do you change your steel, your sharpening angle, or your perception of when to resharpen?
Guys (hardheart & meanwhile), it looks like Jeff Peachey ran up against the kind of problem we ordinary folk have in finding the "best" blade out there. At first glance, I'd say gimme the red knife (T15), but at $715. I'd say, maybe the light blue (A2) would be "just as good" in the long term because while I have to sharpen it more, it is easier to sharpen and a lot less expensive. The tests were purpose driven - leather cutting blades, while we ignorant, (not to mean stupid) happy-go-lucky knife enthusiasts want a knife to cut leather, wood, bone, etc. Assuming T15 could be made into an all-purpose knife, do I want a knife that "never" has to be sharpened, but when it does I need a diamond stone and is very high priced, or it is better to have a mid-range (price) knife that needs re-sharpening, but is easier to do so? I think many of us are looking for that chart like the cable TV folks put out - this package will give you this and next package will give you this plus that, for knives. It may not exist because of the different uses to which we put knives. Yes, we want the easy road to what we each might consider the best knife - a chart that says this knife will cut this bunch of things, but you can't slide it into a rock crevice and hang on it. This here next knife will do all the stuff the first knife does, and you can hang or stand on it - but it costs a lot more. Maybe my $80. Ontario RAT-7 in D-2 [purchased back in 2004] (which I think Ontario stopped making - cause all I see lately is the RAT-7 in 1095) will cut everything I want it to cut, but maybe I can't stand on it or dig my way out of a concrete holding cell in some third world country (where I never intend to be). THAT knife might be way out on the high priced end of the chart. But maybe there is a knife (or TV package) that will get me most of what I think I need for only a little more. Hahahahaha. Just gimme the chart, and I'll figure out which knife to pick for my needs. I don't want to buy em all and find out that the least expensive knife will do everything I need a knife to do except leap tall buildings in a single bound - that there knife at the far end of the imaginary chart.
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In the real world, this is a compromise you often have to make - because initial sharpness is a property of the how thick the edge is and the geometry much more that the blade steel. If you don't do this, then you can only compare using blades of exactly the same geometry.