Sharpening grits and toothiness

S

Shawn7656

Joined
Feb 15, 2012
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So I just remembered I had a microscope in the basement and I grabbed it. I can only focus on the knife using the 10x zoom (the eyepiece is marked 10x as well, so I assume it's 20x?). I was looking at my Tenacious' edge after using a DMT Diafold fine and it looks... terrible. It's super-toothy, and there's little bits of steel that look like they're about to fall off. I just ordered a EF/EEF diafold and it should be here within a week, but I'm curious if my edge is toothier than it should be at the grit I was using.

So how do I know I've reached optimum sharpness and edge quality at a certain grit? I've also been having problems totally doing away with the burr on this steel (8Cr13MoV). It's a very elusive little bugger, though I think I've managed to get rid of it. I usually use my nail to find it by either scraping down the bevel, or running the edge at lower-than-sharpening angle along the back of my fingernail and seeing if it catches. Once I can't feel it at all I make the assumption it's gone. Is there an easier/better way to detect it without magnification?

Another question is when should I be able to reach "hair popping" sharpness? Is it only achievable at higher grits or can I hit it with the DMT fine? So far I haven't ever achieved it and I'm wondering if it's my tools or my technique. The DMT Fine is the highest grit I have at the moment. I have a strop but I feel it makes things worse as the surface is beat up and it doesn't really seem to lay flat. I've been thinking of making my own or buying a different one.



Also, on a slightly unrelated note - My microscope's focus rings do not stay put. I have to hold it in place to keep focus, if I let it go it slowly slides down and out of focus. I'm going to try and figure it out with Google, but does anyone have any ideas on how to fix this little problem?
 
Well, I can only answer two of your questions. I have gotten hair popping sharp with just the DMT fine. But you shouldn't get too caught up in if it "pops" or "whittles" hair or whatever, too many different variables, semantics, etc. If it shaves off hair without scraping off skin, it shaves--anything past that is literally splitting hairs. I'm beginning to wonder if that figure of speech was originated by housewives sick of their husbands honing their knife forever in the endless pursuit of a sharper edge. The tools and techniques needed are simple, it's the results you're seeking that are elusive--too many factors like humidity, hair thickness, hardness, moisture content, ad nauseam. It's fun to chase that dragon of "how sharp can I get it" but don't get too worked up over reaching specific results at that level, because we're talking about a scale that is ridiculously fine.

Anyway, now that my big wordy blow-hard bit is out of the way... Some good ways to detect a hard to find burr:

A needle suspended from a piece of string (let the point drag along the bevel, the string should slack a little if the needle catches a burr before passing over the apex)

Cotton swabs or balls ( the hairs will catch on the burr )

A pen-tube... This one is a bit harder to explain briefly, but it works well... Hold the blade out parallel with the ground, edge turned downward spine upward. Now hold a pen tube at an angle ( the closer to vertical, the sharper the edge needs to be to bite ) on the right-hand side of the spine, see if it bites. Now hold the pen tube at an angle on the left side of the spine, and see if it bites. If there is a burr turned up on the left side of the edge, then the edge will bite into the pen tube if it is on the right side of of the blade, but slide off if on the left side. If the edge bites regardless of which side of the blade the pen tube is on it is burr free

As far as techniques go... The one pointer/tip/principle I find the most useful to remember is to use light pressure, and from what I've found, just when you think you've reached one grit's potential on a specific edge, you'll surprise yourself by honing at even lighter pressure for a little bit longer than you were able to before, and reaching a whole different level of sharpness on that grit than you thought you could--it's kind of like a "ceiling breaker". There are several people here that can get "hair popping" edges off of a DMT coarse, so trust on your tool and think about your technique, don't get too caught up in chasing those insane levels of sharp or persuaded into thinking there is something wrong with either your tool or technique when you don't reach them. Just keep in mind, if your edge is even near hair-popping, you're working in the 99th percentile--everything after that is only going to be that one one-hundredth of a percent sharper.
 
You were viewing the edge at 100x

The diamond is too much for that steel and you will continue to have burr issues through the EEF, use waterstones or oil stones or sandpaper, all will do better.

Sharpen a steel that welcomes diamonds such as S30V or better and a fine diamond produces a very sharp edge.

Using the right tool for the job applies to the stones too ;)
 
You could try a few drops of soapy water on your DMT - might tame it a little and not bite so much on that steel.

One of the best ways to detect a burr without magnification is to get under some strong overhead lighting. Hold the blade up in front of your eyes edge down and slowly tilt it back and forth. At some point the light will be just right - if a burr is there you'll see a tiny halo off the edge. Repeat on the other side. A bit of practice is needed, but once you get a feel for this, NO burr will escape your detection. A loupe is not needed, but helpful.

You'd be surprised at how "clean" you can get an edge even at the lower grit count. Still a fine DMT will look a bit raw at 100x - do not be concerned. When I first started looking at edges under high magnification (640x and 1600x) I was amazed at how rough they looked till I tried looking at ordinary stuff under the same level of magnification and realized even looking kind of rough they were in fact very uniform by comparison.

Getting the most out of whatever grit stone you're using involves angle and pressure control (and removing the burr without making you edge broader). A bevel cut with a DMT fine will have about 25 micron margin of error and still look flat. That margin drops to 9 micron when you move to the EF. A bit of bevel rounding is going to happen anyway, but if there's too much deviation your edge angle is going to be overly large and the apex won't be as cleanly formed as it could be. Pressure is critical too, too much pressure will deform the steel along the apex, esp with diamonds. Use the lightest touch you can manage and still have good contact. Complete and absolute burr removal with a fine DMT might not be possible for some steels without a little stropping. For the most faithful edge to the stone you're grinding with - use plain paper, plain leather, pressed cardboard. These all have some abrasive content naturally, but nothing compared to a strop with compound. Keep in mind the burr must be shrunk to the smallest feathery ghost to remove it with these items.

As mentioned above, a less aggressive stone/abrasive might give you a bit more wiggle room with the steel you're using.
 
End with a strop to get rid of the last bit of burr. don't have a strop? Glue an old leather belt to a paint stir stick. it works well enough on its own or you can get some compound to do it better.
 
Wow that's a lot of info... Thanks guys! I'll probably reread all of that a couple times to make sure I don't forget anything haha

@Kenny: You make a good point with the sharpeness level. I guess I was just thinking since the Tenacious seems to be a great cutter it'd be the knife I tried to reach that level with. Thanks for those techniques, I'll definitely be trying them out.

@Knifenut: I didn't really think about that. I knew they cut fast, but didn't think that'd be my issue. My problem though would be that I only have a super cheap coarse/fine oilstone that's Ace hardware brand and the fine side looks extremely coarse; and then I have a soft Arkansas stone, which also doesn't go too fine but is still finer than the other stone mentioned. Right now I don't have steady income, so I can't really be spending too much on stones. Do you have any recommendations for a good fine oil/water stone in like the $30 range? Or would it be better to just wait until I have more money and invest more?

@Heavyhanded: Thanks for all the tips as well. I guess if I realized it was 100x I may not have been so concerned, but I thought it was 20x lol! I'll definitely look into alternative strops

@clich: I may try that one, as I've got a couple of old belts in the drawer next to me! haha
 
Could try Spyderco Ceramic Double Stuff - Fine/Medium for twenty-five bucks. Use SiC sandpaper (don't use/ruin your diasharp) to lapp to gain a bit finer medium and ultra-fine ceramic. Strop on heavily inked (yep, abrasive) newspaper.
 
I have re-bevelled a couple of knives in 8Cr13MoV from A.G. Russell. I did these using my C/F and EF/EEF Dia-Folds with an Aligner & Magna-Guide. Diamond hones can do great with this steel, but you need to really lighten up on the pressure as you progress to finer grits. Most burrs & wires will always be worse with heavier pressure, on any abrasive. With diamond, there's sort of a double-whammy effect with excess pressure, in that the coarser diamond will strip away far too much metal than necessary, and then burrs & wires will be more of an issue with heavy pressure on finer grits. Make the best use of very (to extremely) light pressure as you progress. By the time you've gotten most of the way through the finest hone, you should've abraded away the heaviest of the burrs, leaving only very delicate burrs that should easily be removed on a strop. If the strop can't remove the burrs, go back to the finest hone and do some more gentle filing on the burrs, then strop again.

If burrs are so small that you can't see or feel them by touch, test how the edge performs when cutting some thin paper, like phonebook pages. Even very tiny burrs usually reveal themselves this way. They'll catch the paper and fold it, instead of cutting it. Or, if the burr/wire is folded over, the edge will slip over the paper without cutting. Oftentimes, very small burrs will collect bits of leather or compound from the surface of a strop also. Much as if you had scraped the strop with your fingernails, the compound and/or leather will collect under your fingernails. Use a magnifier to look for accumulations of this stuff along the edge. Strop the edge on your jeans, and look for the tiny cotton fibers clinging to the edge. That'll usually be a sign of some very small burrs.
 
Shawn7656 said:
Wow that's a lot of info... Thanks guys! I'll probably reread all of that a couple times to make sure I don't forget anything haha

@Kenny: You make a good point with the sharpeness level. I guess I was just thinking since the Tenacious seems to be a great cutter it'd be the knife I tried to reach that level with. Thanks for those techniques, I'll definitely be trying them out.

@Knifenut: I didn't really think about that. I knew they cut fast, but didn't think that'd be my issue. My problem though would be that I only have a super cheap coarse/fine oilstone that's Ace hardware brand and the fine side looks extremely coarse; and then I have a soft Arkansas stone, which also doesn't go too fine but is still finer than the other stone mentioned. Right now I don't have steady income, so I can't really be spending too much on stones. Do you have any recommendations for a good fine oil/water stone in like the $30 range? Or would it be better to just wait until I have more money and invest more?

@Heavyhanded: Thanks for all the tips as well. I guess if I realized it was 100x I may not have been so concerned, but I thought it was 20x lol! I'll definitely look into alternative strops

@clich: I may try that one, as I've got a couple of old belts in the drawer next to me! haha
Click to expand...

I think I have purchased the same stone from Ace hardware actually. 6 x 2 x 1? I thought the fine side didn't look like much at first either, but it does actually put on some surprisingly fine edges so give it a shot. If it's the same stone I expect it will help you.

You could also get a Norton Fine India stone for about $30, but you could also invest in some strops and compounds for that money.
 
3M wet/dry sandpaper from the auto parts store. Most will carry grits from 220-2000.
 
@OwE: Earlier I did go as lightly as I could on the fine Diafold and my edge feels smoother, though I haven't checked it under magnification yet. I regret buying the single-sided diafold, as for only a couple dollars more I could have had the C/F. I did try to return it and buy that a couple days later but they wouldn't let me do it since the product was already used :rolleyes:. Oh well, I guess I can use my oilstones for coarse, and then move to the diamond hones to give it a smoother finish.

@Kenny: That's probably it! I use mine with water though, not oil (I leave it in a little pencil box full of water), not sure if that makes much difference. I can get some nice edges with it - they'll shave, but I haven't gotten em sharp enough to push-cut paper. When I use the fine DMT it puts a MUCH nicer scratch pattern on the blade, and it seems to get much sharper (I noticed this first with my Griptilian). Maybe I just needed to spend more time on the fine side though.

Knifenut: I've been thinking about trying out the sandpaper method. When I worked at Sears (before they closed) I was hoping to buy heaps of it on sale, but they only had coarse grit for power tools, no actual sheets of sandpaper. Maybe I'll pick some up at another hardware store tomorrow. What grits would you suggest I get (from coarse to fine)?
 
I've done some homework on my Ace hardware stone. If its the same as mine its a Vermont American aluminum oxide stone (grey over grey - it looks like a silicone carbide. I've done a side by side to my Norton India stone, the Ace grinds a bit slower, but is capable of every bit as nice an edge. Followed by some white buffing compound (bought mine at Sears for 2 bucks) on newspaper or hard leather you'll have a fairly refined edge - I could just manage to tree-top some leg hair. I highly recommend using some oil or at least putting some dishsoap in the water. Take time and remove as much of the burr as possible, then strop maybe 8-10 times. Use a Sharpie both for managing the grinding phase, and when it comes time to strop, put a couple of dots on the bevel to make sure you're stropping at a good angle and not hitting it too hard or missing the apex entirely.
 
I agree with HH. I get good hair shaving edges on the coarse DMT. So, hair popping is easily capable off the fine DMT. Yet, as said use light strokes. As you advance to the fine the burr should be mostly removed. DM
 
Maybe another important factor is angle... I've only brought mine down to roughly 40 inclusive, possibly a bit higher. Will that allow the blade to get thin enough to "pop" hairs?
 
Lowering it to 30-32 degrees inclusive will help it out in every way. 40 degrees on a single bevel edge is too broad.
 
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