I have been decreasing the edge angle on my Gayle Bradley using the shoulders as a guide.
Finally finished with it and the edge is around 5 Degrees Per Side (DPS). Finished it up on a Spyderco UF stone.
The edge was shaving sharp in both directions and felt very crisp to the touch.
Mandatory glamour shots.
I went ahead and did some woodwork. This piece has been dried out for some time so it was nice and hard.
Results where....well interesting to say the least. Significant edge deformation in terms of chipping.
"If you wish to live and thrive, let the spider run alive" "the perfect knife is the one in your hand, you should just learn how to use it." If you don't have anything good to say, then don't say anything at all
Rerun of the test on the same piece of wood, focusing on an area with a small knot. Did not experience the same deformation.
What can I conclude:
Nothing much, this is just an fyi for those that might have wondered how CPM-M4 might perform at this low angle.
"If you wish to live and thrive, let the spider run alive" "the perfect knife is the one in your hand, you should just learn how to use it." If you don't have anything good to say, then don't say anything at all
That's pretty impressive performance for such a high wear steel IMO. Gunmike used to do stuff like that too. :)
I keep mine at around 30 degrees inclusive. Yes, it could go lower but it has the bite to cut very well, and stays sharp at that with the occasional strop needed. I tend to sharpen more than I really need to as I relax while doing it but with CPM M4 and ZDP I have just learned to leave it alone with the performance I like. Diamonds and my Norton Indias will cut anything I've tried to the point I've had to make it a point not to remove as much steel as I was.
I just enjoy my late night TV with my knife maintenance stuff next to me, and Finn the Mastiff curled up around or on my feet. Simple pleasures. :)
Joe
"A Mastiff is to a dog what a Lion is to a housecat. He stands alone and all others sink before him. His courage does not exceed temper and generosity, and in attachment he equals the kindest of his race" Cynographia Britannic 1800
"Unless you're the lead dog the view is pretty much gonna stay the same!"
Thanks for the thread/experience, mine is around 8dps and had some rolling occur(could have happened from not de stressing before going that low) when cutting through thick cardboard. Did a slight microbevel and it hasn't done the same since then.
78lilred wrote:Thanks for the thread/experience, mine is around 8dps and had some rolling occur(could have happened from not de stressing before going that low) when cutting through thick cardboard. Did a slight microbevel and it hasn't done the same since then.
I'm a bit suprised that at the GB's hardness, the steel still rolls. I would have guessed it to chip.
I went to about 7 dps with the M4 mule but ended up putting a 30 deg microbevel on it. The latter in the hope that it will survive my wife's tendency to cut onto plates instead of cutting boards.
The knife has been used for field and kitchen and I just noticed that as well as a patina there is some pitting developing on the flats behind the bevel. Possibly corresponding to a contact area in the kydex sheath I hastily concocted. Can't say it's been well-cared for by my beloved spouse!
chuck_roxas45 wrote:Thanks for sharing. M4 is wasted at over 30° inclusive, IMHO.
Most steels are IMO. I tend to go as low as I feel comfortable, use it and see if it meets my requirements. If it fails a secondary bevel at higher angle usually resolves most issues. Either way, with a low angled backbevel and small micro/macro bevel I always see an improvement in cutting performance.
Senate wrote:Thanks for taking the time to experiment and post about it!
what's the first double side stone in your vid?
It is a DMT Coarse/Fine Dia-Sharp 6 by 2 inch.
"If you wish to live and thrive, let the spider run alive" "the perfect knife is the one in your hand, you should just learn how to use it." If you don't have anything good to say, then don't say anything at all
That is in general why UH carbide steels are not used in applications when you want to maximize cutting ability, unless the loads are very low and the material very abrasive (like cutting cardboard).
I would be curious at what would be the failure point carbide wise :
-white / blue
-M2
Would be interesting choices of comparison, the first two are common on decent kitchen cutlery.
I would hope that this post and others like it would help to mediate the kneejerk response of ultra high carbide steels every time someone asks about edge retention as the edge retention of M4 was fairly low in the first demonstration on wood and a low carbide steel can easily handle that work.
Although, when the average people ask about edge retention aren't they generally speaking of edge angles in the 12-15 DPS range (or even higher)? In that situation wouldn't a high carbide steel (for most people and tasks) almost always be preferable? At least assuming one is disregarding impact toughness, corrosion resistance, and price.
I guess the best answer to that question is another answer, which most don't ask: "How do you define _____ (better, edge retention, etc) and what are you going to do with it?."
The main reason people use higher angles is just by default. It is a generational thing, people sharpen knives now at angles that you didn't even sharpen axes a generation ago. That is why it is beyond ridiculous to have an edge on a knife at 15 dps and claim the performance is satisfactory when the edge on an axe isn't even at that angle. Just think about this from a general perspective, forget knives for a second. If I gave you a toothbrush and asked you to paint a house would you say it is satisfactory, no - you would say pretty much right away that there seems to be a bit of a problem.
The difference in performance between 5 dps and 15 dps is the same percentage change as from 15 dps to 45 dps. Ask yourself the question if the second is such a trade off of cutting ability for durability that you would reject the knife as even being a knife (no one sharpens that high) - then why would you accept the former so trivially. There is only one reason for the extremely high angles in modern steel, the influence of ultra-high carbide steels and the resultant dramatic loss in durability which is compensated by super thickening of knives to the point the edges exceed where axes were.
If you do any kind of comparison between a low carbide steel and a high carbide steel blade that has an angle at three times as high, the cutting ability decrease will be so low that the edge retention isn't a factor as it is almost impossible to blunt the low carbide steel to reduce the cutting ability so much even in abrasive media. I just did a cardboard run with an custom AEB-L blade at 7-8 dps on cardboard (cKc knives) and it would obliterate the performance of a knife with a 15 dps bevel in regards to extended cutting ability, and 250 m of cardboard cut did noting but lightly cause the edge to reflect light in a very even distribution.
Edge retention in knives is highly dependent on what you are cutting and how. Yes you can trivialize it and answer every question with "the steel with the most vanadium" but outside of really novice users, you kind of want to move a bit beyond that. Plus if that really is the viewpoint then forget steel, use solid ceramic as ceramic makes steels (even steels like 10V) look like brass, they are not even in the same order of magnitude.
I completely understand that it's the default angle and done to keep W&R problems to a minimum on a broad spectrum of buyers. People are becoming less and less empathetic towards tools it seems. Cars, computers, cell phones...really everything we buy is being pummeled to destruction on Day 1. Lol.
When the average buyer is asking for layman answers to the curious question of "edge retention on a Para2", for example, you can either:
1. Explain then nuances of metallurgy and edge angles for cutting performance
2. Assume they mean "working angles" (ie obtuse) and give them the blanket "high vanadium" answer
Most of us here adore the conversation and education. The passerby's don't seem to appreciate it as much.
