Diamonds and feedback/pressure

[KennyB]

I've been using a little DMT D3F diamond credit-card sharpener to sharpen all my knives for a while now. It's great for touch up and heavy repair work, as long as a blade hasn't been heavily damaged I can just sharpen it out on this.

The thing about it though is that, it seems like you can use a lot more pressure and still not produce a burr or blunt the apex versus waterstones. When finishing on a waterstone I have to use extremely gentle strokes of very minimal pressure, but with diamonds it seems like if I don't exert just the right amount of pressure they don't actually do much of anything at all.

Is this normal? It's not as if I'm saying I have to really bear down on the diamond... We're still talking less than knife weight pressures here. It just seems that the diamond abrasive doesn't really do anything at "lighter pressures" that a waterstone would still work at.

I figured that being a very hard abrasive on a rigid substrate, I would have to use very light pressure with the diamond hone versus the waterstone. But it seems to work best with slightly more pressure

Is this just my imagination, normal, or something wrong with my tools?

 

[Jason B.]

It just feels that way. The diamonds cut upon contact.

 

[Obsessed with Edges]

It just feels that way. The diamonds cut upon contact.

That sums it up. An easy way to remind oneself of that, is to 'accidentally' brush a diamond hone on another polished portion of your blade. No matter how light the contact, a scratch (or several) will always be the result. I have countless blades with some really ugly scratches on them, from just an errant, clumsy pass (or two) on diamond hones.

With diamond hones on some steels, it's easy to assume no burr is forming. But on very 'soft' steels (low abrasion resistance) like 1095, for example, it's real easy to create a burr on one pass, unnoticed, and then scrub it off on the next pass. The diamond really does work that fast. It does leave the impression a burr never forms, so it's very important to check the edge very, very frequently as you work. In fact, check every pass, once you know you're close to the apex.

 

[HeavyHanded]

I highly recommend some soapy water on diamond plates. They cut so fast the feedback is not like one gets from a waterstone, or even an oilstone. A bit of lube (for me) greatly increases fine feedback and tames the abrasive action a little bit.

 

[Chris "Anagarika"]

Exactly the kind of feedback I need, as I'm getting a set myself

Thanks!

 

[Komitadjie]

Also, be careful with pushing hard on the diamond plate, that greatly increases the pull-out rate of the diamond particles, and can trash a plate. It doesn't take much pressure at all to get the diamonds to cut!

 

[KennyB]

With diamond hones on some steels, it's easy to assume no burr is forming. But on very 'soft' steels (low abrasion resistance) like 1095, for example, it's real easy to create a burr on one pass, unnoticed, and then scrub it off on the next pass. The diamond really does work that fast. It does leave the impression a burr never forms, so it's very important to check the edge very, very frequently as you work. In fact, check every pass, once you know you're close to the apex.

Hmm yeah I think I have experienced this. Sometimes I'll just run my knife a couple of times over on each side and it will be screaming sharp, but I'll think, "Are you sure that's not just a wire edge?" because of how little work I had to do. That's usually when I try to start using much lighter pressure in hopes of getting it off without raising another burr on the other side, but I think most of the time I just succeed in rounding off my apex chasing an imaginary wire.

 

[Obsessed with Edges]

Hmm yeah I think I have experienced this. Sometimes I'll just run my knife a couple of times over on each side and it will be screaming sharp, but I'll think, "Are you sure that's not just a wire edge?" because of how little work I had to do. That's usually when I try to start using much lighter pressure in hopes of getting it off without raising another burr on the other side, but I think most of the time I just succeed in rounding off my apex chasing an imaginary wire.

When the edge seems 'screaming sharp' like that, it's a good time to do some test-cutting with it, before attempting to 'refine' it further on the stones. A really fine wire edge will often fold or break off when making several cuts into paper or cardboard. I usually notice this after just a few cuts, maybe 3-5, then the cutting changes (starts snagging or it slips without cutting, which indicates a fine wire that has folded). With the paper, slice SLOWLY from heel to tip, so you can watch for any snags. If you can continue cutting with no apparent loss of sharpness, and no new 'snags' or slips of the edge in the paper (I like phonebook paper for testing this), then chances are, the edge is in good shape, and you won't have to chase that imaginary wire with the stones.

More often than not, when the edge is that sharp off the stones, there will still be some little burrs on the edge. Strop it a little bit first, then try the paper-cutting and/or cardboard. In my own habits, when the edge is that close to being 'there', I really start going frequently back & forth between test-cutting the paper, then stropping a few passes, then testing with the paper again. Usually stropping does all the rest, without having to go back to the stones. It does get more difficult to highly refine on the stones, trying to keep pressure extremely light, when the edge is already that fine. As you say, it often goes too far, and ends up being counter-productive. The strops are more forgiving at that stage.


David

 

[Chris "Anagarika"]

Not on diamond but your explanation is what I experienced with a softer steel like older SRM I have. Chasing an imaginary wire, I kept rounding it off until I started tryin stropping (more forgiving).

Thanks!

 

[HeavyHanded]

More often than not, when the edge is that sharp off the stones, there will still be some little burrs on the edge. Strop it a little bit first, then try the paper-cutting and/or cardboard. In my own habits, when the edge is that close to being 'there', I really start going frequently back & forth between test-cutting the paper, then stropping a few passes, then testing with the paper again. Usually stropping does all the rest, without having to go back to the stones. It does get more difficult to highly refine on the stones, trying to keep pressure extremely light, when the edge is already that fine. As you say, it often goes too far, and ends up being counter-productive. The strops are more forgiving at that stage.


David

More and more I rely on stropping on some plain newspaper at this stage. Not only does it add a bit of polish, but any burrs or wires will become much more apparent while maintaining any tooth left in the edge. And it seems to work well at any grit range, can 'refine' some very aggressive edges this way. It doesn't remove any but the smallest of burrs, but is a safe way to find them if you don't want to use a loaded strop and alter the character of your edge.

 

[KennyB]

When the edge seems 'screaming sharp' like that, it's a good time to do some test-cutting with it, before attempting to 'refine' it further on the stones. A really fine wire edge will often fold or break off when making several cuts into paper or cardboard. I usually notice this after just a few cuts, maybe 3-5, then the cutting changes (starts snagging or it slips without cutting, which indicates a fine wire that has folded). With the paper, slice SLOWLY from heel to tip, so you can watch for any snags. If you can continue cutting with no apparent loss of sharpness, and no new 'snags' or slips of the edge in the paper (I like phonebook paper for testing this), then chances are, the edge is in good shape, and you won't have to chase that imaginary wire with the stones.

More often than not, when the edge is that sharp off the stones, there will still be some little burrs on the edge. Strop it a little bit first, then try the paper-cutting and/or cardboard. In my own habits, when the edge is that close to being 'there', I really start going frequently back & forth between test-cutting the paper, then stropping a few passes, then testing with the paper again. Usually stropping does all the rest, without having to go back to the stones. It does get more difficult to highly refine on the stones, trying to keep pressure extremely light, when the edge is already that fine. As you say, it often goes too far, and ends up being counter-productive. The strops are more forgiving at that stage.


David

Ahh good info on testing for them. I've known that you'll lose an edge quickly if there is a wire, but never thought it would be THAT quickly (3-5 cuts). Sometimes too when dealing with these levels of sharpness, it's kind of hard to tell the difference between normal dulling from paper and dulling because of a wire edge so that's a good figure to know.

 

[grizzled gizzard]

I always use soapy water on DMTs. If I don't, the feel and performance change rapidly.

There must be a preponderance of guys using too much pressure. I never hear, "Well ya gotta use more pressure!".

Maybe it's that way for all stones. Guys bein guys, we're all into overkill, but you will pop the grit off your plates if you aren't gentle with them.

I do think diamond plates require some stropping afterword, but I think that about about every stone finish. In my use, no more than normal.

I actually de-burr by running the edge on folded cardboard, like a lot of guys use cork, or soft wood. I fold a piece of cardboard into a tent shape, and use that "top edge". It's always handy, and eminently disposable.

I final test for burrs cutting phonebook paper, nice and slowly.

 

[OHALLUM]

"I final test for burrs cutting phonebook paper, nice and slowly." As quoted by Grizz.

I take a Q tip and lightly run along the edge to check for snags or burs. If one is present, you can feel the drag, and if big enough, you can see the cotton hanging up on it. If your edge is nice and smooth, and you can drag the Q tip along it without any snags, then I try the phone book paper test. Works great for me, and the wife can't complain about the missing pages from her phone book.

Omar

 

[grizzled gizzard]

That's a good (Q)-tip, Omar.

 

[Obsessed with Edges]

Ahh good info on testing for them. I've known that you'll lose an edge quickly if there is a wire, but never thought it would be THAT quickly (3-5 cuts). Sometimes too when dealing with these levels of sharpness, it's kind of hard to tell the difference between normal dulling from paper and dulling because of a wire edge so that's a good figure to know.

That's why I've developed a preference for using phonebook paper for this. When I first started using it, it was just a matter of convenience, and a fun way to 'dispose' of old phonebooks I had (I call it 'poor man's shredding'). I noticed though, when doing the SLOW cutting in the paper, it was a very good indicator of the burrs or wires being there. Just the slightest little irregularity in the edge would cause the paper to snag and fold over, or sometimes little fibers of the paper would be left hanging at the burr location, like a little flag saying "Here it is!". And as mentioned, it usually didn't take long to notice the change in cutting, if a wire edge folded over. The flipside to that, if the edge was in good shape, I could keep slicing away, to my heart's content, and it'd just keep cutting like a laser beam.

Some steels are more resistant to the burr/wire folding or moving, like VG-10 (at hardness typically found in Spyderco's blades) or 420HC (Case). But in both of those examples, the wires are usually big and/or stubborn enough to been seen/felt by other means, such as with your thumbnail. They are usually much more obvious.

 

[Jason B.]

Just wanted to clear one thing up. A wire edge is very ridged and not likely to move, it is from excessive grinding to one side. It will stay in place for the duration of the cutting experience in most cases.

A burr is movable and will cause failure during cutting typically from collapsing on the apex. You don't get the same failure from a wire edge because its a larger and more solid formation of metal.

 

[KennyB]

Just wanted to clear one thing up. A wire edge is very ridged and not likely to move, it is from excessive grinding to one side. It will stay in place for the duration of the cutting experience in most cases.

A burr is movable and will cause failure during cutting typically from collapsing on the apex. You don't get the same failure from a wire edge because its a larger and more solid formation of metal.

Hmm, so what is the best way to really tell if you have a wire edge then? I've noticed that with some of the more "mild steels " (14C28N and 1095) that they lose the initial bityness and hair-whittling-ness (but still slice the paper and shave hair okay ) after cutting up about two pieces of phone book or receipt paper. Does that sound like a wire edge, or more like normal abrasion?

 

[grizzled gizzard]

Just wanted to clear one thing up. A wire edge is very ridged and not likely to move, it is from excessive grinding to one side. It will stay in place for the duration of the cutting experience in most cases.

A burr is movable and will cause failure during cutting typically from collapsing on the apex. You don't get the same failure from a wire edge because its a larger and more solid formation of metal.

If you don't mind me asking, where did you learn this?

If you had a wire edge, a swipe or two on the other side would make it a burr, or an apex?

When you say,
" It will stay in place for the duration of the cutting experience in most cases."

What does that mean? It kinda sounds like a good thing.

How would a burr collapse, and land on the apex? I'm entirely missing that.

Ho much magnification does it take to see this?

 

[Obsessed with Edges]

My 2 cents' worth:

To me (as I view it), the difference between a 'burr' and 'wire edge' has more to do with it's length (along the edge). I view 'burrs' as little irregular snags or bits of loosely connected and weak steel at random spots along an edge, and a 'wire' as a thin sliver of weak steel running a significant length of the edge. Both of which result from the very same grinding/sharpening process. And I see some wire edges that are thick & stubborn and don't want to be moved easily, and some that are very thin, which more easily break off and/or move or fold. Very ductile steels, like the VG-10 and 420HC I mentioned earlier, will form a wire edge more easily which, if abraded & thinned further, eventually behave and break away like a burr (albeit running a longer length of the edge).

All that aside, how each is defined is essentially moot to me, as they're both essentially impediments getting in the way (quite literally) of a good cutting edge. I was looking around at different sites today, reading other discussions of the topic (wire vs burr). How each is defined is as variable as whichever 'expert' defines it. Some 'definitions' describe the 'wire edge' as a thin, long sliver of weak steel that's essentially aligned with the cutting edge (straight up/down), and the 'burr' as the very same thin sliver, but folded over to one side or the other. I don't see anything resembling 'consensus' opinion of it, certainly nothing that could be interpreted as THE definitive answer. And to me, it seems somewhat trivial in the bigger picture.

 

[OHALLUM]

Some say tomaato, some say tomahhto. I say they are both great on sammiches!

Omar