Sharpening difficulties are they due to attributes of the steels or technique?

[me2]

I had very good results sharpening CPM S60V using 320 grit SiC sandpaper and my Sharpmaker. I think there has to be more to it than just hardness of the abrasives when sharpening the high carbide steels. Of course diamonds are an improvement, but I've nvever had any trouble getting a sharp edge on my high alloy steels like S60V, M2, 440C, 154CM, etc. all of which have carbides in significant quantities that are harder than the old Norton India stones I used and the Aluminum Oxide in the 204 rods.

 

[KennyB]

I had very good results sharpening CPM S60V using 320 grit SiC sandpaper and my Sharpmaker. I think there has to be more to it than just hardness of the abrasives when sharpening the high carbide steels. Of course diamonds are an improvement, but I've nvever had any trouble getting a sharp edge on my high alloy steels like S60V, M2, 440C, 154CM, etc. all of which have carbides in significant quantities that are harder than the old Norton India stones I used and the Aluminum Oxide in the 204 rods.

Well, I've noticed that even S30V takes a little bit more grinding than other steels without high V. I'm not sure how much Case uses in CV, but it's the only steel I've used that takes about the same amount of grinding.

I've noticed a benefit of using diamonds on both of these steels in that if I reprofile using a 220 Norton, and then put a 750 grit Smith's diamond hone into the progression, then I can raise a burr on my 1K Norton much more quickly than if I had gone straight from the 220. Of course this makes sense considering the grit progression, but the 750 diamond surface does seem to cut disproportionately fast on these steels.

 

[ultrafine]

me2

Yes there is, regular non porous aluminum oxide (HIP/sintered or whatever) has a kind of rounded edges, but i think some whetstones from naniva or shapton have fuzed sliced ellipses that cuts much more aggesively since material can get under it and around it in another way. Really cutting it off like a knife, not just making scratches on the surface type of action..

 

[cziv]

Another post for a specific topic. My method is modified a little from Jeff's original, so you may want to search out the "right" way. But, here's how I do it, and how I use the 204 in general. I think of it as a final finish/touch up tool mostly, though I have rebevel several knives with just the 204. When using my 204, I also use micro bevels. It takes a lot of time to use the 204 to polish all but the narrowest edge bevels.

First, get a burr formed evenly along the edge. I have used a belt sander, a coarse Norton India stone, a slow turning water wheel about 18" across, and currently my 220/1000 grit waterstone. I have also used the 15 degree/side setting on the 204 with the brown rod corners, doing 50 to 100 strokes on one side, then switching, until a burr is formed after using each side. It's important that the bevel be slightly less than the desired Sharpmaker (204) setting, 3-5 degrees or so. This is what gives you the micro bevel. If you don't have a way to control angles, its not that critical, it just needs to be less.

Then use the Sharpmaker as shown in the video, though I generally do about twice as many strokes as recommended. I do it just to make sure I get the large scratches out from using the coarse stones. You could also use a medium grit before going to the Sharpmaker, which is why I use a 220/1000 grit combo stone now.

The difference comes when you want to change grits on the 204. Before moving from the brown flats to the white corners, or from the white flats to a strop, I use the following procedure.

Whatever your angle choice, hold the knife parallel to the opposite stone, basically double the sharpening angle. Do a couple of VERY LIGHT passes, alternating, on each side. This will remove the burr, if any. Do this on a new/clean side of the stone. This maximzes the cutting action. After this, go back and give the edge about 10 to 20 strokes per side, alternating, at the normal angle. Voila, a burr free edge.

I do not do this on the corners of the stones. The small radius puts too much pressure on the edge and can form a new burr in one pass through bending of the edge. The flats are relatively small, so care is needed here too, but they're not nearly as bad as the corners. For the pressure needed with the high angle strokes, imagine your 204 is sitting on a roller skate, and you are not holding it with your off hand. If the skate moves, you're using too much pressure. This is a slight exaggeration, but it makes the point. I generally set the base on the counter and if it slides, I'm pushing too hard.

This procedure has worked on every steel I've tried, from CPM S60V to 1095. I have not tried S30V, or any of the steels developed to compete with it, though success with S60V indicates any steel should work.

That's what I recall about the method in question.

At the end of sharpening. Do 1 or 2 high angle

hold the knife parallel to the opposite stone, basically double the sharpening angle

passes on the fine flats like holding a 60* angle tilted away from vertical (up to down) strokes on your 30* setting, which peels the burr right off. Do both sides the same. Finish the edge with about 6 - 10 extremely light passes at the correct angle. Good job me2! :thumbup:

 

[dipbait]

I became much better at sharpening after reading this.




Jeff Clark
Platinum Member

Join Date: Apr 1999
Location: Colorado Springs, CO USA
Posts: 6,038
The problem is with your sharpening technique, not with stainless steel. Carbon steel is more forgiving of mistakes. It makes everybody seem like a sharpening genius.

Burrs form when you remove more than the minimum amount of material to reach an edge. The burr is the remnant of the material that you thought you removed from the apex of your edge, but in reality it folded away from your hone as you worked. Even with a light touch you can get some burr, but using excessive honing pressure (particularly on a narrow honing surface like a ceramic rod) will cause a larger fraction of the edge to bend out of alignment. So first of all use light pressure as you approach the end of your honing process. Another thing that maximizes a burr is honing on one side at a time. As you get to the later phases of your honing be sure that you are honing on alternate sides of the edge on every stroke (left-side, right-side, left-side, right-side...).

A burr forms because your hone's abrasive particles are not shaving off little bits of the edge like a razor blade. The particles varie from rounded, to pointy, to flat-topped. They shave off some material, but they also have a tendency to simply plow through and bend over some of the blade material. If the blade is extremely brittle like glass it will microchip as you hone it. If the blade material is softer it will not chip, but it will tend to do some burr formation as soon as your edge gets thin. If your carbon steel knife is 58 or 60 RC hardness it will form a bit less burr than a stainless steel blade that is 56 or 58 RC. If your stainless steel has large chromium carbide grains in it those will tend to fold over rather than get cut.

The sure way to debur an edge is to lightly hone edge-forwards at an angle that is significantly greater than your normal honing angle using an abrasive that cuts more than simply polishing. When I do most of my honing at 15 degrees I will bebur using clean medium-grit ceramic rods at 25 degrees. It only takes about 8 light strokes to do it (left, right, left, right, left, right, left, right). Then I go back to 15 degrees and restore my edge with a minimum number of strokes. If you go back and hone too much you will just create another burr.

You may actually still have a burr on your carbon steel blades. Carbon steel is easy to push into alignment and it forms a fairly sturdy burr. For years I happily used burred carbon steel blades. They shaved great and I didn't notice that they dulled faster than they should have. For a kitchen knife you might be happy if you just pushed your burrs into alignment by a little light stroking on smooth ceramic rods or on a smooth steel. You could do the same thing if you sort of lightly hone a burred edge on the side of a glass. Remember to work on a soft cutting board in the kitchen.
__________________

 

[TheCarbideRat]

wow, gold. Thanks! :thumbup:

 

[me2]

me2

Yes there is, regular non porous aluminum oxide (HIP/sintered or whatever) has a kind of rounded edges, but i think some whetstones from naniva or shapton have fuzed sliced ellipses that cuts much more aggesively since material can get under it and around it in another way. Really cutting it off like a knife, not just making scratches on the surface type of action..

Yep, particle shape, particle strength, bond strength, hardness, toughness, and porosity all play a part. That's what I meant by there is more to it than just particle hardness.

 

[David Martin]

I have to comment on this as dipbait's post was very good . Technique has a lot to do with sharpening . Find a technique that gives good results and repeat it . You only have to learn that one thing . Yep, me2 I agree, theres more to it than hardness of compounds and the stone material . As I have sharpened S30V on Norton's SiC stones . These are good quality stones . But just based on the hardness of this material would lead one to think this could not be done . I've even rebeveled S60V on the same stone . Go figure ! Diamond will cut it, leaving a better edge and not dish . But the gray stones are good . Don't be mislead to think the hardware store gray stone quality is near what I speak of . DM

 

[Noctis3880]

So true.

And almost no carbides can be clean cut with aluminum oxide.

Hardness in knoop:

Aluminum oxide - 2100
Silicon carbide - 2500
Diamond - 7000
Cubic boron nitride - 4700

Carbides:

Martensite - 1000
Cementite - 1400
Chromium carbide - 2200 (so even this is uncuttable with aluminum oxide..)
Niobium carbide - 2400
Tungsten- and Vanadium carbide - both 2800

And this is why VC/WC-heavy steels really need Diamond (since no fine grained SiC stones exist anyway and they still come up short)

Getting a chip in s30v for example is a real nightmare if all you have is a sharpmaker or similar. Since all you can do is grind away the soft martensite matrix, and then when enough is ground down, rip out the harder carbides.

If you think about it, aluminum oxide is pretty much the opposite of what you could call a good abrasive for any of the higher alloyed allegedly high performance, "super steels", and aluminum oxide is pretty the only thing everyone has.

Message to SAL@Spyderco: how about you release CBN coated-rods in 1k,2k,4k or similar ranges for the sharpmaker?? You know pushing the envelope..

Cpm S90V and 15V contains 9 and 15% vanadium, you can sharpen this until the cows come home, nothing will ever happen, the knife industry needs new sharpeningmedia..

It's interesting you say this, because I've managed to sharpen CPM-M4 on my paper wheels(silicon carbide grit on one wheel and white rouge on the other) with relative ease. If anything, I've found my ZT 0301 in S30V to be harder to sharpen than my Gayle Bradley in CPM-M4(which might have something to do with the thickness of the blades).

I can't say with 100% certainty until I actually get my hands on S90V, but I feel the main problem has to do with actually machining the blank S90V blades into a usable knife shape. Though I did sharpen my Shallot in S110V to a nice paper push cut sharpness pretty easily:thumbup:.

 

[me2]

IIRC, Phil Wilson sharpens his knives on the same Norton Coarse and Fine SiC stones, and he uses some of the latest alloys at hardnesses others cringe over. Of course, he also grinds the edges to match the intended use, so there is not an excess of metal to be removed, making everyone happier.

 

[THG]

I was sharpening Cold Steel AUS8A today and I noticed the same thing with the burr. It was hanging on for dear life. I got it squared away though.

I had the same experience. The burr just wouldn't go away.

ZDP-189, on the other hand, was an easy steel for me to sharpen. Sure it took longer, but I could much more consistently get that super sharp edge.

 

[awestib]

Hi,

Remember, the video is made to address the majority of users w/o overly complicating the matter. When I start talking about burrs, grinds, and angles, all I get is polite smiles or blank stares. For most people, the technique in the DVD will work.

For us knife people, we get into the science of things.

So here's what I recommand:

Use the diamond rods or sandpaper wrapped rods to set your edge angles. In this case, burrs don't matter as long as you get the two sides to meet. So I tend to alternate 10 strokes or more per side until I get a consistent edge along the blade. This is also where I make sure the two sides are even and the grind is centered. That means one side may need more work than the other to even things out.

After the edge is set, on the medium rods, I start on one side until I get a burr to form on the opposite side. Then I switch and repeat on the other side. This will make the burr flip to the other side. I reduce the number of stokes per side and repeat. (For example, if it took 15 strokes on the first set, I go to 12, 9, 6, etc. for the next sets) until I get to a couple of light alternating 1 stroke sets. I lighten up the pressure as I go through these steps. The burr should reduce in size and thickness as you progress. By the end, there should be a very weak thin burr left.

I switch to the fine rods and start refining the edge with light pressure and a couple strokes per side. I use a good light source and examine the edge to see my progress. Once I'm satisfied that all the rough scratches are gone, I do some light alternating strokes to finish off. If the burr is still there, I run the edge lightly through a soft material to break it off. A piece of wood, the plastic base of the SM or something similar. Then I make a few more LIGHT strokes and check again. When that burr is completely gone, you're done.

If you're looking to go even further, break out the UF rods and repeat the steps from the fine rods. We're using even less pressure and now we're trying to prevent a burr from ever forming. When you're done, you should be able to easily pop hairs and even whittle hair.

I won't get into stropping since that involves a whole new set of techniques. If you do a proper job on the UF rods, it basically does the same thing as stropping.

My best tool for checking the edge has been to use a pocket microscope to check my edges through the process. A jeweler's loupe is almost as good.

I have been trying to get a burr on my Benchmade D2 knife on the brown (or dark grey?) rods on the sharpmaker after profiling the edge with diamond rods to 30 degr but I don't seem to get that done even after doing it on one side for a long time. I even tried to move the blade up and down and was very careful to keep the blade straight. I probably did more than 100 strokes or so and still nothing? Maybe I just can't feel the burr? Any advice?
Thanks!

 

[Jason B.]

I don't have much problem keeping my blades sharp using rods, stones and sandpaper but I also don't do as much sharpening as probly alot of you guys do so my question is about what can make a knife hard to sharpen as i have heard about some knives [these in particular are 440C but comments about any steels are good] which are hard to get an edge on. I've also seen threads about how some knives are almost impossible to get an edge on or at least they are giving someone quite a challenge, what gives?

99% Technique
1% Abrasive

 

[THG]

I have been trying to get a burr on my Benchmade D2 knife on the brown (or dark grey?) rods on the sharpmaker after profiling the edge with diamond rods to 30 degr but I don't seem to get that done even after doing it on one side for a long time. I even tried to move the blade up and down and was very careful to keep the blade straight. I probably did more than 100 strokes or so and still nothing? Maybe I just can't feel the burr? Any advice?
Thanks!

If your bevels are above 30°, you are reprofiling your angle, and 100 strokes is nothing. Use a sharpie and spread some lines along your bevels. Do a few passes and see where the marker is coming off. If it's coming off right at the edge, then you're sharpening. If it's coming off at the shoulder where the bevels and body of the blade meet, then you're reprofiling, and your knife isn't going to get sharp.

If you're reprofiling, it can take thousands and thousands of passes to reach the edge. And if you're using the brown stone of the Sharpmaker to do it, then it can take tens of thousands more (it's actually a relatively fine stone.)

 

[TheCarbideRat]

Lots of good comments, I got a microscope for $10 at Radio Shack, I think it's a wise investment for sharpening.

 

[THG]

Lots of good comments, I got a microscope for $10 at Radio Shack, I think it's a wise investment for sharpening.

I got that and returned it the next day. It was extremely difficult to use (hold still, find what you're looking for, focus it, get the proper lighting, etc.)

But then again, I do have a tabletop microscope with the same power.

 

[TheCarbideRat]

I see, so how much that babe set you back?

 

[THG]

I see, so how much that babe set you back?

Honestly, I can't remember. I got it over 10 years ago. It's nothing special at all, though; it's got a 40-100x magnification lens, and it uses a mirror at the bottom for lighting. I don't think it could have been over $100.

 

[cziv]

I went to a college nearby and once every year or so they'll unload some microscopes. I mean the "bomb" m-scopes, with a bunch of lenses and internal lighting. You can see your skin ( after you slice a piece off by accident ) and see the cells, nucleus etc.. $100 but they're few and far between. I'd put an ad in Craigslist and do searches in local nearby Craigslists.

 

[awestib]

Another post for a specific topic. My method is modified a little from Jeff's original, so you may want to search out the "right" way. But, here's how I do it, and how I use the 204 in general. I think of it as a final finish/touch up tool mostly, though I have rebevel several knives with just the 204. When using my 204, I also use micro bevels. It takes a lot of time to use the 204 to polish all but the narrowest edge bevels.

First, get a burr formed evenly along the edge. I have used a belt sander, a coarse Norton India stone, a slow turning water wheel about 18" across, and currently my 220/1000 grit waterstone. I have also used the 15 degree/side setting on the 204 with the brown rod corners, doing 50 to 100 strokes on one side, then switching, until a burr is formed after using each side. It's important that the bevel be slightly less than the desired Sharpmaker (204) setting, 3-5 degrees or so. This is what gives you the micro bevel. If you don't have a way to control angles, its not that critical, it just needs to be less.

Then use the Sharpmaker as shown in the video, though I generally do about twice as many strokes as recommended. I do it just to make sure I get the large scratches out from using the coarse stones. You could also use a medium grit before going to the Sharpmaker, which is why I use a 220/1000 grit combo stone now.

The difference comes when you want to change grits on the 204. Before moving from the brown flats to the white corners, or from the white flats to a strop, I use the following procedure.

Whatever your angle choice, hold the knife parallel to the opposite stone, basically double the sharpening angle. Do a couple of VERY LIGHT passes, alternating, on each side. This will remove the burr, if any. Do this on a new/clean side of the stone. This maximzes the cutting action. After this, go back and give the edge about 10 to 20 strokes per side, alternating, at the normal angle. Voila, a burr free edge.

I do not do this on the corners of the stones. The small radius puts too much pressure on the edge and can form a new burr in one pass through bending of the edge. The flats are relatively small, so care is needed here too, but they're not nearly as bad as the corners. For the pressure needed with the high angle strokes, imagine your 204 is sitting on a roller skate, and you are not holding it with your off hand. If the skate moves, you're using too much pressure. This is a slight exaggeration, but it makes the point. I generally set the base on the counter and if it slides, I'm pushing too hard.

This procedure has worked on every steel I've tried, from CPM S60V to 1095. I have not tried S30V, or any of the steels developed to compete with it, though success with S60V indicates any steel should work.

I tried your method on my Benchmade folder D2 steel after I ground a 30 degr. primary and a 40 degr secondary with the diamond rods. I was quite happy after I finished with the medium rods, I was able to slice paper without problems. However, the blade/edge is not sharp enough to shave hair from my leg? I actually was quite surprised and I don't know what else to do to improve my sharpening technique?!
Any advice?