Sharpening consistency

[kennyj]

So... did a metric f$%&ton of research on sharpening technique, sat down with my Sharpmaker and attacked my Sebenza (I know, I know, but it's my EDC and I dulled the edge.) I did see immediate improvement and over the past few days my technique has improved, but my early mistakes are haunting me.

Looking closely at the blade (no magnifying lenses or anything) I can see that one side along the flat portion of the blade has been ground more than the other, and that the angle is a bit different in fact. I've been working away at the knife to even this out, but it persists. The edge is essentially "off" to one side a bit. Not rolled; it just hasn't been ground evenly and as such it's not centered.

The curved portion hasn't gotten as sharp as the flat portion yet; it's most evident when testing the edge by cutting newsprint as the portions cut with the curved part of the blade are rougher and require more effort. It also shows when I attempt a hair-popping test; the closer I get to the tip, the fewer hairs that the edge grabs onto.

At least, I haven't destroyed the tip (yet.) I've kept myself from pulling the knife off the hones, instead stopping the draw with the tip still on the hone. I've slipped a few times, though, and between that and my inconsistencies, the tip isn't in very good shape. It's still "pointy" but the edge is dull. It also looks like it may have been rounded or blunted very slightly, but I could be paranoid and over-analyzing it. More than likely, it's still dull because it just hasn't been sharpened enough, but at least it's still a little pointy.

Is there any good way to make sure I get the edge centered again and get the angles on each side even? Does this even have anything to do with cutting performance as long as the edge is still facing forward? (I keep remembering that chisel grinds do actually work...) And last but not least... what's the best way to keep that tip nice, pointy, and sharp? I tried freehanding the tip with one of the stones, using it like a file, but it seems that all I accomplished was some scuffing-up of the finish.

 

[Cliff Stamp]

I can see that one side along the flat portion of the blade has been ground more than the other, and that the angle is a bit different in fact.

It is very common for freehand sharpening to induce a an angle bias due to the user being left/right handed. While the Sharpmaker is usually lumped in with jigs, there isn't strict clamped angle control. Note as well if the primary grind is asymmetric if you grind at the exact same angle the edge will be uneven in width.

The curved portion hasn't gotten as sharp as the flat portion yet; it's most evident when testing the edge by cutting newsprint as the portions cut with the curved part of the blade are rougher and require more effort. It also shows when I attempt a hair-popping test; the closer I get to the tip, the fewer hairs that the edge grabs onto.

The edge in the tip is often at a more obtuse bevel so it takes some time before the Sharpmaker is actually hitting the edge. You also need to rotate the knife to keep the edge perpendicular to the stones and be careful of grinding the tip along the stone as you will square it off.

Is there any good way to make sure I get the edge centered again and get the angles on each side even?

If the edge is off center to fix it you just grind on one side until it moves back in line. Considering how abrasion resistant S30V is and how difficult this makes it to grind I doubt that it is highly asymmetric anyway you are most likely seen an effect of an uneveness in the primary. To get the angles really even then focus more on technique. Considering the problems you are having I would recommend taking a very coarse stone and freehanding a 15 degree bevel. This will radically increase ease of sharpening as well as cutting ability and edge retention. You should then be able to restore the edge to shaving sharpness in well under a minute on the Sharpmaker from an edge which doesn't slice paper.

Does this even have anything to do with cutting performance as long as the edge is still facing forward?

No, generally not, lots of knives are highly asymmetric in nature, the differences induced by a small asymmetry in angle is very difficult to notice. Generally this is more of a concern for primary grinds and even then you can compensate with cutting technique and you will only notice it on cutting binding media which has certain properties.

-Cliff

 

[kennyj]

That's encouraging... I might try using some wet/dry automotive sandpaper I have laying around, otherwise I think I can pick up a coarse stone locally.

I was actually going for a 15 degree secondary bevel, and grinding a more acute primary. I'm starting to think that a part of my problem is that I didn't grind the primary thoroughly enough or consistently enough, so I might still be fighting remnants of the original grind that should've been removed when the primary was established, but weren't. That'll teach me to forego the magic marker trick...

My end goal was to end up with a concave primary bevel and a 15 degree V-grind secondary bevel so I'd ideally have a high degree of sharpness, good, efficient blade travel, and simple, idiot-proof maintainance with the Sharpmaker. I actually got an even and gradual looking cocave bevel with my pseudo-freehand work but it might be too fat for this purpose, owing to insufficient sharpening time considering just how wide and obtuse the original edge was compared to where I'm trying to get it. Perhaps I'll be better off just freehanding the primary at a straight 10 degrees or so.

If I indeed squared the tip off to some extent, is there a good way to re-establish it? That sounds like something I might have done, and it would definitely explain the appearance it now has (it's not far from normal but it's "off" in some way.)

Thanks for all of the advice!

 

[db]

I have the same advice to fix your uneven problem as Cliff. Sharpen on the side that the edge seems to be towards. This should move it back to center and it may take a few times to do it. Free hand works too you can even use that coarse sandpaper on a flat piece of glass like a bench hone if you want. Sand paper is a fairly good choice to use if you cann't find a coarse stone locally. There is a few threads floating around where Cliff and I disagree on edges and sharpeningand have different ideas on if they matter or not. I personally like to fix them and get them looking good and even. I think most people do too. It's easy to blame the prime blade grind but it's unlikly that is the reason for it. It's more likely you did sharpen too much on one side and then sharpening on the other will move it back. There is a fairly long and good thread on just this problem I'll find and bring it up for you to look at.

 

[kel_aa]

It's easy to blame the prime blade grind but it's unlikly that is the reason for it. It's more likely you did sharpen too much on one side and then sharpening on the other will move it back.

This is S30V with a factory bevel. Your beard will grow down to your lap before you start to skew that on a Sharpmaker.

 

[db]

He said he has been doing it for the last few days. So yeah he probably did sharpen on one side too much. Did you and Cliff learn to read at the same school?

 

[Cliff Stamp]

This is S30V with a factory bevel. Your beard will grow down to your lap before you start to skew that on a Sharpmaker.

I actually reset the initial bevel on my Sharpmaker to 20 degrees, not 15, just 20 and it took 1050 passes just on one side. I was curious as to just how long it would take. I intended origionally to reprofile to 15 but wasn't that curious. You will also see a huge burr form if you keep grinding on one side after the edge meets.

That's encouraging... I might try using some wet/dry automotive sandpaper I have laying around, otherwise I think I can pick up a coarse stone locally.

You can use paper, just get really coarse, you want to actually be able to feel the grit. If you have a magnifier you can save yourself a lot of frustration and some steel because you generally want to stop just before you hit the very edge unless you want to leave the edge at the coarse bevel. This is especially true at low angles because a 90 grit silicon carbide stone will tear pretty big pieces out of a 10 degree edge so a lot of steel is wasted if you bring this back to a full polish compared to stopping just before the coarse scratches start to hit the edge. It doesn't happen that fast though, even with x-coarse hones I still do cycles of 100 passes per side when removing just micro-bevels on really wear resistant steels. Once you sharpen a few steels you get a feel for how long it takes so you are not checking that frequently.

I'm starting to think that a part of my problem is that I didn't grind the primary thoroughly enough or consistently enough, so I might still be fighting remnants of the original grind that should've been removed when the primary was established, but weren't.

Yes, that is the exact problem the majority of the time. It takes a really long time to grind off steel on the high wear steels in general. You really want to micro-bevel and just hone the primary with really coarse hones as a shaping step.

Perhaps I'll be better off just freehanding the primary at a straight 10 degrees or so.

If you are just cutting soft materials yes, no twisting in thick metals. Watch the opening stud though or you will grind into that readily at low angles. Tilt the blade on the stone so you don't grind into it. You can go even lower if it is just a cutting tool, mine is 5 degrees and I have only chipped it by cutting into a nail (carving flooring, the nail had broken off), and opening a bunch of food cans trying to see if I could figure out a way to do it without chipping the edge - I did eventually, it isn't that hard to do actually. The cutting ability is fairly extreme at that profile and the ease of sharpening is really high. However the primary bevels will get really wide and you will scratch the primary.

If I indeed squared the tip off to some extent, is there a good way to re-establish it?

Regrind it by cutting into the stone to establish a curvature. Use a marker to black out what you need to remove to give you a guide.

-Cliff

 

[kel_aa]

From Cliff's Review of the Sebenza
The small Sebenza has a blade length of 2.94" made by stock removal out of 0.125" thick S30V stainless steel hardened to 58/59 HRC with an overall length of 6.875" when opened. The handle maderial is 6Al4V Titanium. It weighs 80 g and the steel is 0.118" thick at maximum. The blade has a maximum width of 2.2 cm with a 1.75 cm high primary hollow grind which tapers to an edge ground at 0.012-0.014" thick and beveled at 14.6 +/- 0.9 degrees per side.

I don't quite understand. The inital bevel was at about 15 degrees already, why did you reset it to 20? Additionally, you noted that yours was ground thinner than usual, if I remember correctly?

Db, your point is well made. Kenny, you better check your table. Maybe one of the legs is a couple of inches longer than the other. And better go get some gyros from from the university physics lab. Prehaps my fat ass in Canada is distorting the the space- time continuum and causing you to sharpen crookedly.

 

[Cliff Stamp]

I don't quite understand. The inital bevel was at about 15 degrees already, why did you reset it to 20?

The edge had a obtuse secondary bevel as noted in the sharpening section. So I was just taking off a secondary bevel. The edges are also lightly convex so they are lower at the shoulder and higher at the apex. The angle given is that of the intersector as Hob noted in his recent commentary about convex edges and how to quantify them. I should probably note that in the review.

Additionally, you noted that yours was ground thinner than usual, if I remember correctly?

Yeah, half of the aimed specifications, most of it was from one side so when honed flat to the stone the bevel is way wider on one side than the other. The really sloppy side is the one in the pictures which is kind of ironic on many levels.

-Cliff

 

[kennyj]

I went through quite a few sheets of 220 and 320 sandpaper, and a few small sheets of 400, 600, and 800 grit. I found that a simple clipboard did a decent job of holding the sandpaper steady and flat, though the limitations were readily apparent - now I really want one of Hand American's PSA setups, whenever they finish their month-long pricing update.

The angle wasn't the same on both sides and on one side there's a few inconsistencies when going from choil to tip, but they smoothed out a bit as I had to spend that much more time on those areas each time I went up in grit. Considering how rough the papers were I knew I was going to be lucky to get an identifiable burr (instead, I just got a rough, almost pitted edge) so I used a magic marker as my guide - paint the edge, remove the marker, and repeat once before going up in grit. The job wasn't perfect by any means (I didn't spend as much time as I wanted at any point because I kept running out of sandpaper) but it worked out well.

The edge I had after using the 800 grit paper was probably somewhere around 20 degrees all-inclusive, maybe as low as 15. Wasn't really useful, though, as it was still coarse and unrefined. A few parts could shave, but it looked more like I was snagging hair than anything else.

Over the coarse of the job I was able to thin the grind around the tip slightly and bring it in a bit. The difference is subtle, but the result is that the bevel is normalized and the tip appears to be re-established. If nothing else, it's almost needle-sharp to the touch.

Took the Sharpmaker out and the 15 degree bevel setting made short work of the edge, making it scary sharp in no time. I have bald spots on both arms to prove it. I'm not sure whether the knive shaves or the hairs just flee down my arm in fright...

The secondary bevel isn't really established near or at the tip. I'm going to finish it up when my hands aren't as tired; I spent about three hours on this project. I might even get more sandpaper and work out the less-consistent parts of the grind, and might also go a few grits higher if only to make the finish more attractive, but I'm pretty happy with it now.

At least I'll never have to grind that much metal off this knife ever again... it blew me away how quickly I wore out each sheet of sandpaper. Cleaning one would only slightly improve it; it was as though the knife ate through the grit just as quickly as it ate at the knife.

Thanks for your help, Cliff.

One last question, I hope: is there an easy way to sharpen a tip on the Sharpmaker without rounding it off, or is freehand really the easiest way?

 

[Cliff Stamp]

The edge I had after using the 800 grit paper was probably somewhere around 20 degrees all-inclusive, maybe as low as 15. Wasn't really useful, though, as it was still coarse and unrefined. A few parts could shave, but it looked more like I was snagging hair than anything else.

This is a common effect of edge trailing sharpening, especially on dry sandpaper which has a static cling effect. Generally I use a couple of burr removal passes into the paper at an elevated angle when I switch grits. Just go light and only a very short travel on the paper. Not every steel needs this, some are just prone to burred edges.

Took the Sharpmaker out and the 15 degree bevel setting made short work of the edge, making it scary sharp in no time.

Once you work with micro-bevels you will never return to full bevel sharpening again. You will notice a gradual increase in sharpening time as you hone it from one session to the next as the micro-bevel thickens and eventually you will want to recut the primary. I generally never let it become significantly visible. However it never takes a significant length of time compared to the initial honing.

... it blew me away how quickly I wore out each sheet of sandpaper.

One of the many joys of vanadium carbide.

One last question, I hope: is there an easy way to sharpen a tip on the Sharpmaker without rounding it off ...

On the end of the stroke, rotate the blade so the edge is perpendicular to the stone and *don't* pull it off the stone, end it with the tip contacting the base. Nice work on the Sebenza, I bet it cuts exceptionally well now.

-Cliff

 

[Greg]

The initial bevels and edges of a Sebenza are (I suspect) done on a belt grinder. My Sebenza needed a fair bit of work to get the primaries even width and to the same angle. I prefer a guided system with diamond hones for this.
Please note that sharp edges are very thin!!! and can easily be deformed by using a Sharpmaker. The micro-bevels that Cliff mentions are best formed by VERY light strokes (which is why I now finish all my edges on a paper wheel). Ongoing sharpening is a couple of strokes with a leather strop loaded with polishing compound.
Greg

 

[kennyj]

The original edge on the Sebenza is, in fact, done on a belt grinder. CRK specifically states that they do so with a final bevel of 19-20 degrees. However, anecdotal evidence appears to suggest that it's either very thick until right before the edge, or that the final edge is at a more obtuse angle than that (perhaps being unintentionally rounded off slightly to a higher angle.) My own Sebenza wasn't particularly sharp at first, even compared to other knives I own with worn 20 degree edges, so I do wonder just where the original edge stands.

I'm actually going to get a strop and refine the edge further when I do, then use that for touch-ups. For now, the Sharpmaker seems to do a decent job of getting a very usable edge on my Sebbie and maintaining it easily. No problems with the edge deforming, at least for me. Once my skill level gets a little higher, I'm probably just going to stick with the strop and keep the sharpmaker for serrated blades and the like.

Given that I seem to have accomplished a convex primary bevel, there's still a bit of meat behind my edge. Nothing like what it had with the original profile, but more than enough to give it a decent amount of strength. It hasn't deformed yet, and it glides through cardboard, newsprint, etc. with ease. It also cut open some hard plastic packaging a lot more easily than I'm used to.

There're still some improvements to be made, but I'm not going to bother until I get a strop and some other equipment. All I really plan to do in the end is even out the primary bevel a bit, partly to improve consistency and partly to make the secondary bevel easier to grind (the angle changes a couple of times on one side by a small amount and that causes it to be a bit harder to sharpen properly.)

 

[Cliff Stamp]

Ongoing sharpening is a couple of strokes with a leather strop loaded with polishing compound.

How blunt do the knives get before you give them a touchup?

-Cliff

 

[Greg]

I don't know, not very dull.
When they are sharp I can feel them cut into and 'stick' on the cutting board as I work. Generally I strop once or twice a week on my most used chef's knife. I understand it is about RC 52. The comfortable handle and wide blade were more important than hardness when I bought it.
Greg