How Do You Define Sharp?

[Dean51]

I think HeavyHanded nailed it, how much you finish the edge will define how sharp it is.
I use a KME diamond system at 20 degrees per side, not what most would consider shaving sharp and definitely not tree topping. It is sharp none the less and 20 degrees is a good working angle. Once you get it worked with the 1500 grit diamonds it is sharp. I can then strop it with Bark River black then green compound to very sharp. Sharp doesn't have to shave that's what your razor is for. 20 degrees per side will hold up well cutting cardboard but 15 per side not nearly as well.

 

[jtho8774]

Sounds like you have a rounded edge apex. How do you achieve the shaving edge?

Ill buy that. I was working a sharp maker overtime on this particular edge. Near reprofiling with a medium sharpmaker rod. Certainly could be rounding the edge, working so hard and for such a long time and losing focus. Trying to keep that angle for an hour trying to reach the apex, i knew it could get somewhat convexed, ugh i dont know. Maybe ill go to the wicked edge, i guess i know just enough about sharpening to get me in trouble

 

[Ajack60]

With any knife I use for work, when I start getting hot spots on my hand from using that knife, it's time to sharpen it. For me, it's silly to put a mirrored hair whittling edge on a work knife. That's for me bragging knives. I keep my kitchen knives the sharpest or any knife I may use for the kitchen. I like to have my light users extremely sharp. I typically two knives, one for work and one for light use.

 

[T. Erdelyi]

If you can shave with an ax, its been sharpened in incorrectly. If you can split wood with a scalpel it been sharpened incorrectly.

Well said Fred, I think people tend to over sharpen their knives over this shaving sharp knife idea. I can sharpen almost anything to hair splittin' scary sharp but depending on what I use it for determines how long it stays that sharp. If all I'm doing is shaving arm hair it'll stay sharp forever.

Two things I do, I keep a razor sharp Case Swayback Jack in my pocket just for the purpose of showing off and I also carry a regular working edge blade that's a compromise between razor sharp and wood splitting sharp.

The nice thing about carrying a few different blades or even a traditional multi blade pattern like a Stockman which gives me the option of different degrees of sharpening for different tasks.

To answer the OP as to how I determine sharpness, you know those disposable foam ear plugs for working in noisy environments?

It takes a razor/scalpel sharp knife to slice cleanly through the ear plug without compressing the ear plug. If your blade is even the slightest bit dull it won't cut it, just flatten it.

Try it and you'll find out how really sharp it is. I'd be interested to hear how anybody does.

 

[yakantosh]

For my pocket knives, I prefer to have an edge sharp enough to glide through newspaper easily. For my hard working knives, I like the edge to just be able to shave. I found that if I sharpened them to be scary sharp, the edge would dull out on me a bit to quickly.

 

[me2]

Ill buy that. I was working a sharp maker overtime on this particular edge. Near reprofiling with a medium sharpmaker rod. Certainly could be rounding the edge, working so hard and for such a long time and losing focus. Trying to keep that angle for an hour trying to reach the apex, i knew it could get somewhat convexed, ugh i dont know. Maybe ill go to the wicked edge, i guess i know just enough about sharpening to get me in trouble

Are you using a lot of passes on the corners of the medium stones? As mentioned earlier you may have a small burr. I don't see a way to round the edge on the ceramics of a Sharpmaker (204). I had thought you might be buffing the edge on a power buffer or maybe doing a lot of stropping with heavy pressure, both of which will round the edge. Try deburring on the medium stone flats. To do this, use Jeff Clark's deburring procedure. Whatever angle you're using, when you feel you're getting a sharp edge that doesn't have any aggression, raise the angle by holding it parallel to the opposite rod and making a pass on each side. This doubles your sharpening angle (either 30 or 40 degrees per side), and will cut off any burr. Go very light, and just make one or 2 passes per side. Then go back and make alternating passes at the normal angle. There's also a chance you're not actually hitting the edge, but I don't see how if you can shave your arm. It's hard to grasp, but cutting technique on paper is highly variable, and may be your source of frustration.

 

[HeavyHanded]

On the subject of edge finish strategies, I find the shaving, high polish edge on my axes, hatchets, and machetes to be well worth the few extra minutes. The steel on these tools is relatively low RC and very easy to rapidly finish to a fine polish with a bit of practice - the reduced friction leads to a much easier time chopping and the edge tends to last a surprisingly long time (as long as you don't lend it to anybody). Is also how I prep my Chef's knives used primarily for chopping and dicing - to a high polish. I came to this conclusion by prepping a few small knives to varying finishes and testing them on different materials. Was amazed at the diameter of green branches that could be chopped clean with a hair whittling edge on a 3.5" blade, while a somewhat toothier edge would barely penetrate the bark and only a little into the wood beneath. Cutting heavy canvas and rope, the roles reversed in favor of the toothy edge. Generalities, but very informative.

 

[jtho8774]

Are you using a lot of passes on the corners of the medium stones? As mentioned earlier you may have a small burr. I don't see a way to round the edge on the ceramics of a Sharpmaker (204). I had thought you might be buffing the edge on a power buffer or maybe doing a lot of stropping with heavy pressure, both of which will round the edge. Try deburring on the medium stone flats. To do this, use Jeff Clark's deburring procedure. Whatever angle you're using, when you feel you're getting a sharp edge that doesn't have any aggression, raise the angle by holding it parallel to the opposite rod and making a pass on each side. This doubles your sharpening angle (either 30 or 40 degrees per side), and will cut off any burr. Go very light, and just make one or 2 passes per side. Then go back and make alternating passes at the normal angle. There's also a chance you're not actually hitting the edge, but I don't see how if you can shave your arm. It's hard to grasp, but cutting technique on paper is highly variable, and may be your source of frustration.

Yeah, I did try deburring at a greater angle with the medium stone, few light strokes on piece of soft pine wood, strop a little with compound, stropped it on my jeans, I mean I tried everything I could think of to get rid of a burr and it would shave hair on both sides of the blade. I am aware that cutting paper can sometimes be a little difficult even if the knife is sharp and I don't need the knife to cut paper as a chore, I'm just trying to see the condition of the edge. I never could decide if I was ready to move to a fine stone. Anyway did send the knife off to be sharpened so it's gone now. Sorry if I got off track or didn't get to respond to all your questions but I really appreciate your interest and responses

 

[me2]

Think of it as a trade of information. Can you email me how things are from the sharpening service? I've recently started wondering what I might be missing, having sharpened my own knives since I was 12 (39 now). It sounds like you either still have a burr or have a highly stressed edge. I had similar experience with some kitchen knives a few years ago. While I was sharpening it just wouldn't get sharp. Then I watched the burr just break off on the coarse stone. After that, I put an edge on it straight off the Sharpmaker that would whittle hair etc. No stropping needed. I talked to the owner and she said it was a wedding present (20 years earlier) and had only been steeled (eek) for that entire time. That explained a lot.

 

[HeavyHanded]

Ill buy that. I was working a sharp maker overtime on this particular edge. Near reprofiling with a medium sharpmaker rod. Certainly could be rounding the edge, working so hard and for such a long time and losing focus. Trying to keep that angle for an hour trying to reach the apex, i knew it could get somewhat convexed, ugh i dont know. Maybe ill go to the wicked edge, i guess i know just enough about sharpening to get me in trouble

What steel is this particular tool made from?
Anytime I hear someone working for an hour with no real progress, a couple thoughts come to mind based on my own experiences:

The stone is plugged, glazed, or otherwise incapable of really working the intended steel. The SM rods are supposed to work most fare, but something like 110v could give em trouble. When an abrasive, for whatever reason, becomes too mismatched with a given steel, the quality of the grind falls way off - burr removal become very difficult, and at the micro scale the abrasives are no longer digging cleanly in the steel. Throw in a high volume of Vanadium carbides and the edge quality will fall way off.

Your mechanics could be a bit off, and the cutting bevel is becoming very convexed - not so much rounded off as in overworked on a strop, but rounded as in each pass is hitting in a different spot and the apex angle is off a handful of degrees from the intended angle. This will not only make grinding a new edge take a loong time and limit the number of passes that are actually directed at the apex itself, but will also result in an edge that lacks a lot of "catchiness". This can be observed as you rotate the edge under strong lighting - the edge will display a lot of curvature in the reflection (or not).

Best of luck with the sharpening service - did they mention what means they normally use?

 

[Czechmate]

On the subject of edge finish strategies, I find the shaving, high polish edge on my axes, hatchets, and machetes to be well worth the few extra minutes. The steel on these tools is relatively low RC and very easy to rapidly finish to a fine polish with a bit of practice - the reduced friction leads to a much easier time chopping and the edge tends to last a surprisingly long time (as long as you don't lend it to anybody). Is also how I prep my Chef's knives used primarily for chopping and dicing - to a high polish. I came to this conclusion by prepping a few small knives to varying finishes and testing them on different materials. Was amazed at the diameter of green branches that could be chopped clean with a hair whittling edge on a 3.5" blade, while a somewhat toothier edge would barely penetrate the bark and only a little into the wood beneath. Cutting heavy canvas and rope, the roles reversed in favor of the toothy edge. Generalities, but very informative.

Interesting that you mention this; I've found it to be true on my hatchets...:thumbup: Still LOL'ing at the last part in brackets.

I consider tree-topping arm to be sharp or the three finger sticky edge test like Murray Carter does.

 

[HeavyHanded]

Interesting that you mention this; I've found it to be true on my hatchets...:thumbup: Still LOL'ing at the last part in brackets.

I consider tree-topping arm to be sharp or the three finger sticky edge test like Murray Carter does.

It cannot be repeated enough! I've had my old Fiskars hatchet hold an edge that started out face-shaving sharp and was still able to shave arm hair after 5 camping trips when it was only used by me. I wasn't exactly building a log cabin or anything, but firewood for two nights per trip - I like a good sized fire when I'm backpacking. Loan it out and invariably the top corner of the bit will be chipped for starters.

The only time I managed to trash an edge in short order was when I cut up a cedar log that had washed up on the shore of Racquette Lake in the Adirondacks. It must have been loaded with fine sand and minerals as it got pushed up to the high water mark. My edge literally looked like I'd been chopping steel wool or slamming between two sheets of sandpaper. Note to self, do not chop driftwood for the fire (unless using a borrowed hatchet )!

 

[bdmicarta]

I'm far from an expert on sharpening. I use a DMT Aligner kit and then some quick stropping with a homemade strop. If I do a full-blown sharpening job I will usually get the knife to the point where it will easily slice newspaper.

I don't normally need a knife to be that sharp for my uses, but I sharpen it that way just because I can. Once a knife gets a little dull I might just strop it a little bit and keep using it. My normal use is cutting open boxes, cutting string or thin rope, maybe some light woodcarving. Just for grins I tried some of the mass cardboard slicing to see how much I could slice and how fast the edge would dull. That proved that an edge can feel dull but still be useful and that's all that I normally need.

In reality I have a lot of knives in my EDC rotation so once I sharpen one it will stay sharp for a long time.

 

[awestib]

... and the cutting bevel is becoming very convexed - not so much rounded off as in overworked on a strop, but rounded as in each pass is hitting in a different spot and the apex angle is off a handful of degrees from the intended angle ...

That reminds me of some of my earlier edges when doing more 90-degrees-to-the-stone forth and back strokes and otherwise not paying enough attention. Yes, I got a burr, flipped it, everything looked good - until I tried to remove the burr with single edge leading strokes. It just took too long so something was off. Under magnification (I only have a 10x lupe) I saw, particularly on the belly, the light reflection clearly indicating a rather convex bevel. Not really facetted but convex. I guess I was "rocking" unintentionally too much. Since I have been using a rather 45-degrees-to-the-stones "sideways" motion, the bevels are flatter and burr removal is easier. Took me a while to figure that out. The Spyderco Sharpmaker actually helped me in solving this mystery. Since the bevel are virtually dead flat due to almost perfect angle control, burr removal was always very easy, usually one stroke, 2 the most.

My goodness - there is so much to sharpening - lucky us ...

Sorry for this sidetrack - thought it may be interesting!

 

[Doug557]

I m new to serious sharpening,, so I'm learning, but think I know what u mean, does the edge seem real polished and doesn't give a toothy bite? If so, sounds like u stropped too hard and rolled the edge over , when u push too hard on the strop the leather gives and wraps around the knife and rounds edge, so next ti,e. Do t press down so hard when Stropping.