edge holding vs sharpening

J

Jack Goertz

Joined
Feb 28, 1999
Messages
91
Here's a question which may open a can of worms. Is there a direct relationship between difficulty of sharpening and edge holding? Asked another way, if it's easy to sharpen does it automatically dull more easily? The reason I ask is, I touched up a friend's ATS 34 Applegate blade this AM on a little diamond hone - a few swipes, a burr, a few the other way, and there it was. This steel is supposed to be 59 to 61 RC and hold an edge very well. One would think, based on this, that it would dull easily. Are there other factors which determine edge hold vs ease of sharpening? If so, what might they be?

Jack
 
Ease of sharpening (i.e., time required) is a function of hardness, but edge thickness and sharpening angle are also important factors. If you have to remove a lot of metal to thin out the edge, it can take a long time. It also makes a difference what kind of sharpening surface you are using. Obviously a course diamond surface will remove metal faster than a surgical black Arkansas hone.

To get a really good edge can be difficult with some of the softer and cheaper steels, because you don't get a good burr, or when you do, it's difficult to remove--it just flops from side to side when you alternate strokes.

David Rock
 
I find that wear resistance is wear resistance. If it takes a long time to wear the steel away in use, it'll take a long time to wear it away on the sharpening stone.

However, wear resistance isn't the last word in ease-of-sharpening. Sometimes, a very hard steel that has a lot of wear resistance is relatively easy to sharpen, because (I'm guessing) it's happy with very few molecules of steel at the very edge. On the other hand, a very soft steel with low wear resistance might be hard to sharpen to a razor edge -- you can sharpen away steel quickly, but have trouble grinding off the burr (as David Rock said), or the steel just seems unhappy with very few steel molecules at the edge. Someone a couple years ago compared sharpening the softer 400 series steels to sharpening soap -- yeah it's soft, yeah you can grind the soap away easily, but soap doesn't want to take a good edge.

Joe
jat@cup.hp.com
 
Joe, here's a follow up question. A friend is looking at a deer hunting knife in 1095. He's looking at a custom knife. What kind of RC rating can he expect, what kind of edge holding, and how difficult is it to sharpen. He's complained about a friend's Buck (perhaps it's 425M, but I don't really know). It's hard for him to sharpen and doesn't hold an edge. He's looking for an improvement.

Thanks.

Jack
 
Jack,
If your friend want a custom 1095 knife, send him to Newt Livesay. I love Newt's products and hope to be buying many, many more of them soon. My next planned purchase from Newt will be several of his neck knives and the ICU. I don't know what the hardness of Newt's knives happens to be, but they seem to hold an edge fine for me and are easy to sharpen. (I don't have much trouble sharpening knives though.)

[This message has been edited by the4th (edited 06 April 1999).]
 
Is there a direct relationship between difficulty of sharpening and edge holding?
Click to expand...
I sure hope there is such a relationship. Seldom content to leave well enough alone, I recently decided that a Bauchop Alley Cat Fighter could use a more acute edge so I set to work with my Lansky system. After M-A-N-Y hours of work, I've almost finished reprofiling the edge.

I'm no newbie when it comes to sharpening but this is the first D2 blade that I have tried to reprofile. Prior to this experience, I had no motivation to buy Lansky's diamond hones. Now, before I attempt such a Herculean task again, I will definitely have something better suited to the job on hand.

However, rather than automatically ordering the Lansky diamond hones, I want to ask if anyone can suggest a viable alternative. I've read great things about the Sharpmaker, but how suited is it to sharpening and/or reprofiling ultra-hard tool steels? TIA.

------------------
--+Brian+--
 
As a follow up comment to Joe's, the Mirage-X line from MD is very abrasion resistant but because it does not burr at all, it is not difficult to sharpen and you can quite trivially put a final bevel on the edge within a few minutes. I compared the cutting performance of an operator at x-coarse, fine, x-fine the weekend and the sharpening was much quicker than the cutting.

[the x-coarse edge won - no surprise, details to follow]

-Cliff
 
bcaffrey,

About reprofiling with the Sharpmaker... I can tell you it is a real bear to reprofile ATS-34 (BM 710) using only the medium sticks of the sharpener. I don't know if there are coarser sticks other than the diamond sleeves (which, I hear, have been discontinued). Fortunately, I shouldn't have to reprofile any more BM 710's.

O_D
 
Outlaw Dogboy,

Thanks for the info. Since I previously reprofiled an ATS-34 blade without anywhere near the amount of work as this D2 blade -- granted, the ATS-34 blade was considerably thinner -- I guess the Sharpmaker is out of the running for this purpose.

------------------
--+Brian+--
 
Brian for serious reprofiling on the Sharpmaker use Joe's suggestion of leaning an x-coarse stone against the sticks and sharpen on that.

-Cliff
 
Jack --

As far as what your friend can expect from that 1095 hunter, he can't EXPECT anything at all. He will need to ask the maker how he did the heat treat and how hard he left the edge.

1095 can be differentially tempered or hardened, and can take a high hardness for excellent edge holding for uses like hunting knives. So the range of performance for 1095 as you typically see it ranges from great-toughness-and-okay-edge-holding to awesome-edgeholding-and-good-toughness. It will perform incredibly well if the edge is hard enough. If the maker leaves the edge soft, then there's going to be a lot of performance left on the table.

Joe
jat@cup.hp.com
 
Thanks for passing on the tip, Cliff. It certainly sounds like a way to improve the versatility of the Sharpmaker.

My present quest, however, is to find something that will do a more effective job of reprofiling really hard steels than what I have. I started out on the Alley Cat's D2 blade with the Lansky extra coarse hone(70 grit) and it did work, albeit very slowly.

I've just about finished with the primary edge but haven't touched the swedge yet and don't intend to until I have a more effective way of doing it. I'm considering ordering the Lansky diamond hones but, @ > $70 for the set, I wanted to learn what others might have to suggest.

------------------
--+Brian+--
 
Brian, you do not need the hole set of the Lansky Diamond hones if you have the standerd set. Just get the extra course diamond for re-profiling a blade and use the standerd med. and fine hones for the rest, final sharpening.
Another thing I have done is mounted a bench stone on a block of wood and drilled a hole for the gide rod and a screw to hold it. Now I can use the Lansky clamp with a bench stone that I have and it works better than I thought it was going to. It is what I use when I have to take alot steel off. Then I just use the med or fine honeto put on the final edge.
 
While a diamond stone will remove metal faster than say an alumina oxide stone when light pressure is used on both, when you use a lot of pressure the AO stone really runs the metal off while the diamond pad just gets stripped.

One thing to consider is that when you are just reprofiling you don't need to be all that accurate with your first cut at setting the bevel. Even if you can't get a really nice edge freehand you should be able to get a decent initial bevel without any jigs. Once the bulk of the metal is removed you can then switch to a system that sets the angle like a Lansky and refine it. You can buy Japanese waterstones with really low grits (like 250) that are huge (4" x 12") cheaply, and they are great for rough beveling.

Awhile ago Joe posted a major refining job on his CS SRK, he did the initial reprofiling fairly rough with a file and then used the Razor's Edge clamp and an x-coarse hone to even it out. Some of the harder steels will not take to a file well, but the point is still the same, you don't need to be that precise on the first cut.

-Cliff

 
Thanks for the tips, DB & Cliff. I probably will go with just the extra course diamond hone for now & see how it works out. I've used a file in the past when beginning to reprofile totally unsharpened false edges but didn't want to chance possible problems with the custom piece.

Cliff, can you recommend a good source of Japanese waterstones? I may have overlooked them, I don't recall seeing them at online dealers. Also, do the grits for these use a different scale? You mentioned 250 being a very low grit, yet the Lansky medium hone is a 280. Thanks again.

------------------
--+Brian+--
 
Hmmm... This reminds me of what happened to my homemade small bowie knife a while ago.

I was showing it off to a couple of friends of mine by slicing everything I can think of. After doing nth number of slices on thick cardboard boxes and some abaca hemp ropes, the edge finally dulled. A few swipes on my arkansas-like stone (dunno what this is really, just got it from my dad), it was back to its hair-popping sharp edge (edge is convex, btw, similar to the Moran blade). The steel is ball-bearing steel as far as I can recall. It's supposed to be pretty tough, though I was wondering how come only a few swipes on the stone gave its edge back if it was really hard steel? Is it the edge angle? the bevel? or something else? I was cutting through stuffs that were known to dull blades easily.

Not that I'm complaining.
smile.gif
It actually feels good to be able to put the edge back there (thanks to Joe T.'s teachings, hehe) manually. I'm just thinking why it's so easy to put the edge back on a steel type that's known to be very hard.

Any clues?

Dan
 
Brian:

http://www.leevalley.com/

And yeah, the Japanese waterstones use much higher grit values. A 4000 is like a 1200 DMT. So a 250 is really coarse, I think that's the big green slab. DMT's are great as you don't have to use much pressure and they never hollow out - but the waterstones are lots cheaper.

Dan, its much easier to restore a very tough edge because it generally doesn't deform it just flattens a little bit. A few swipes on a stone or steel gets it back into shape fast. If the blade is on the other hand really soft, it tends to flop around, get impacted, chip out etc. and requires much more effort to get back into shape.

Along the same line, high alloy steels for example are more trouble to maintain that low alloy ones because the more carbides the bigger chunks of the steel matrix that break off. Of course the more carbides the more abrasion resistant and the longer the times between sharpening.

-Cliff
 
Hi Cliff..
smile.gif
Thanks for the info. That was a sigh of relief. lol... For a while there, I was beginning to feel that this steel is too soft since around two passes on the whetstone gives its edge back.
But it doesn't chip, not even when I hit it on bone. So I guess the steel is really hard. Maybe I should change the edge profile to make the edge last longer? Ah well, I guess I'll try to experiment on it.
smile.gif
I dread to think what I'll do if I did chip the edge soon, putting back the convex edge will be a tough one.

Thanks again pal.
smile.gif


Dan
 
Thanks again, Cliff. Lee Valley's "stone pond" looks very interesting.

------------------
--+Brian+--
 
Dan, I would. None of my knives have the same edge bevels on them as none of my knives are used to do the same thing. Finding the optimal bevel is not difficult but just time consuming. I generally do it gradually. If the edge doesn't chip out, the next time I lower it a little to get better performance. I keep doing this until it gets too fragile and then I just go back up one step - bingo - I not have the optimum mix of cutting ability and durability. You do bring up a good point on the chipping issue which is why you don't see a lot of heavy use knives in the high sixties in RC. Yes they would hold their edge on soft materials forever, but would chip out easily on harder stuff and be a lot of trouble to maintain.

Brian, yeah, it stops you from making a mess. I hacked one together and it works well enough. Lee Valley also has some very nice cheap plastic angle guides for sharpening. While I would not reccommend them for serious use they will quickly allow an inexperienced person to get a decent edge on a blunt knife.

-Cliff

[This message has been edited by Cliff Stamp (edited 09 April 1999).]
 
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