I have noticed in the last few months that a few of my knives burr more easily than others. Specifically, my Kershaw Chive and Skyline. I can get these blades sharp, but not shaving. Using a basic sharpmaker. I don't think its the 420HC on the chive, because I regularly sharpen my Leatherman tools with no problem. I feel like I get excellent results with the sharpmaker, I am wondering if I am doing something wrong, or if I need to get a finer stone for some steel.
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Burrs and Steel
- Thread starter Smash05
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Some steels do tend to form a burr more than others. Sharpening technique and type of stone or media being used is a factor. Using too much pressure (like, when you're getting impatient) tends to make for a bigger burr, and a less durable edge when you're finished, so I would try using lighter pressure. Also using a coarser grit stone for most of the job, applying only the finish edge as a microbevel at slightly higher angle with your fine Sharpmaker rods, can help. But make sure to remove any burr before applying the final edge ... Jeff Clark has posted an excellent technique for burr removal using the Sharpmaker at elevated angle, maybe someone has a link to those instructions and can post it.
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Pressure is a big factor with the spyderco ceramics, using a lot of pressure will make them work fast but will create a large burr. This is not a problem but when you finish up use very light pressure to take the burr down to almost nothing. The UF ceramics will produce a almost perfect burr free edge when used in this way. A strop would be a big help in your case.
Some burrs are crumbly and wire-like. They can be cleaned off by using very light, cleaning strokes on the stones for the last few rounds. Also, increasing the angle and using light strokes works. Another method is to run the edge lightly through soft wood. I once saw a burr like this get raked off by making a gentle stroke on the corner of a SharpMaker rod. You could see the thing peel off.
Other burrs are more deeply rooted and tenacious. Instead of a nearly detached, wire like burr, these are more like the edge is just curled at the microscopic level. This type is more problematic and is what I usually get on the SharpMaker. I think the back-and-forth action of the SharpMaker tends to limit burr formation except for this type. Using heavy strokes encourages these to form. Once they form, they won't go away. They just flop back and forth when you try and remove them. You either just align the thing straight with the edge and live with it, or you cut it away by making direct perpendicular cuts into the stone (light pressure) to square off the edge in preparation for your next attempt at forming a clean edge. 420HC behaves this way on the SharpMaker for me. I can't make it go away once it forms. I use very light pressure to avoid these. Another strategy is to start by using diamond stones to form a clean bevel intersection and then use the ceramic rods to refine and polish. The diamond abrasives cut more cleanly whereas the ceramics tend to push metal around more blunt like.
Other burrs are more deeply rooted and tenacious. Instead of a nearly detached, wire like burr, these are more like the edge is just curled at the microscopic level. This type is more problematic and is what I usually get on the SharpMaker. I think the back-and-forth action of the SharpMaker tends to limit burr formation except for this type. Using heavy strokes encourages these to form. Once they form, they won't go away. They just flop back and forth when you try and remove them. You either just align the thing straight with the edge and live with it, or you cut it away by making direct perpendicular cuts into the stone (light pressure) to square off the edge in preparation for your next attempt at forming a clean edge. 420HC behaves this way on the SharpMaker for me. I can't make it go away once it forms. I use very light pressure to avoid these. Another strategy is to start by using diamond stones to form a clean bevel intersection and then use the ceramic rods to refine and polish. The diamond abrasives cut more cleanly whereas the ceramics tend to push metal around more blunt like.
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I must diagree with almost everything you say. The burr forms when your two bevels meet and start over lapping. Once you equal the angles the burr only starts to be removed, the burr at this point is nothing more than the edge not being able to be ground any thinner than the stone/abrasive allows. To properly finish your edge you must use some sorte of micro-abrasive, I like diamond spray on leather.
The burr that is there after your done on your final stone is not the same as the one you get on a coarse stone. here are some pic's hope they help in understanding what I just said.
These pic's are taken at 130x zoom and are of a M4 mule.
edge after UF ceramic, the shiny balls on the edge is the burr. This burr is almost unable to be felt but its their.
Same edge after being stropped with 0.5 micron diamond spray. Notice the shiny burr is gone and the edge is closer together. If you want to see how sharp it is look at the records page.
gunmike1
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Knifenut1013, that is a very good shot showing a burr and it's removal via strop. I have found, after LOTS of practice, that I can "sneak up" on a burr and stop sharpening at each grit prior to forming that small, pesky wire. I frequently use my lighted radioshack microscope and also frequently check the knives for certain milestones of sharpness at each grit (how it shaves, tree tops, pushcuts newsprint, ect.) and when I am having a good day I don't even form a wire edge. Most of the time I am using microbevels, though, which makes it easier as there are very few strokes required at each grit to get the knife sharp. I also go to overkill and go edge leading into 3M lapping film as fine as .05 microns for that super fine edge, but even at 1000 grit or less I can get hair whittling sharpness without the burrs (I have a few posts in the sharpness records page, as well). It just takes lots of practice and OCD, not to mention lots of time. After getting back surgery recently I think I may be looking into some of those paper wheels that Richardj promotes to save my back from spending so much time hunched over bench stones.
Oh yeah, and when I am having a bad day at the stones, I do just like you did and strop (though I use the lapping film) to remove the last hint of burr if slightly raising my angle won't do it (that usually works for me). If you go edge leading into that lapping film with a burred edge you will almost instantly gouge into it and rip the lapping film. Lighted magnification is definately a requirement for making sure you have a real edge, and not a burr waiting to rip off and kill you sharpness immediately.
Mike
Oh yeah, and when I am having a bad day at the stones, I do just like you did and strop (though I use the lapping film) to remove the last hint of burr if slightly raising my angle won't do it (that usually works for me). If you go edge leading into that lapping film with a burred edge you will almost instantly gouge into it and rip the lapping film. Lighted magnification is definately a requirement for making sure you have a real edge, and not a burr waiting to rip off and kill you sharpness immediately.
Mike
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where do you get lapping film that fine?
No prob. I'm always learning!
gunmike1
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I got 1 micron and .3 micron from tools for woodworking I think. I forget where I got the .05 micron (maybe precision surfaces international?), but it cost about as much in shipping if not more than for the lapping film itself. It does make a difference over the .3 micron in sharpness, but I'm not sure I would pay that much for more again out of principal. Plus, I find that at this point 1 micron is kind of going to excess in anyway, let alone .05 micron. My OCD just makes me keep going though!
Mike
Gunmike, I think I may be using the same 0.3 micron films you are. I got them from the local woodworking shop. Its abrasive on Mylar, with PSA backing. I can go from chipped and dull to hair whittling in 3 steps on my favorite kitchen knife. I usually use the Sharpmaker in between for other knives, as a bench stone. The high angle burr removal step is great when using the Sharpmaker alone. Also, a knife with a beaten up edge will form a more tenacious burr than one that has not been abused. Try doing a few light cuts directly into the medium Sharpmaker stones to remove any damaged/fatigued metal from the edge, then sharpen normally. Jeff Clark's deburring explanation is better, but until he chimes in, I'll summarize. Before moving to the final honing step, the fine white stones in my case, take a couple of high angle strokes by laying the knife parallel to the opposite stone, so making a 60 degree angle if using the 30 degree slots. Take a couple of light strokes at the high angle to remove the burr, then do a few more (dozen or so) normally and the burr should be gone. This wont always work with soft steels or on blades with fatigued edges. It does work on my kitchen knives though, which are mystery steel, but quite good for the money. Jeff's method is a little more involved, but I've not had to go that far yet. Also, do the burr removal on the flats of the triangles, to lessen pressure and keep from making the burr worse. Sometimes its necessary to do the burr removal step on the white stones too.
Its a useful technique for difficult to remove burrs, and absolutely necessary for coarse grit shaving edges. I dont do it unless I'm having trouble. I did it for years when in high school, and didnt realize the other benefits except that I knew I wanted the entire edge at the same starting place. The fishhook groove in the Sharpmaker triangles works well for cutting into the edge and uniformly dulling/removing burrs.
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gunmike1
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How would this have any effect on a sharpening burr?
By cutting off any steel that was fatigued during cutting. When you are cutting things up it obviously damages the steel and you lose your edge that you had sharpened the knife to. In my opinion some of the steel still sitting there on the blade is fatigued and weak, which loves to form those pesky burrs during sharpening the just don't want to go away. Plus, I usually resharpen my blades when a lot of people would still consider them somewhat sharp, and I like to start from the same starting point, dead dull, every sharpening. That way I know my coarse edges that I am putting on are from my fresh sharpening and not my left over edge. I learned this technique from Cliff who shall not be named years ago and it has really helped me to minimize forming burrs during sharpening.
Mike
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Sounds pointless to me, if your starting with a coarse stone then your removing enough metal already. It also does not do anything for helping the burr while sharpening.
I don't let my knives get dull either and usually touch them up on a UF ceramic before stropping. I have never experienced any weak edge problems.
I don't let my knives get dull either and usually touch them up on a UF ceramic before stropping. I have never experienced any weak edge problems.
gunmike1
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Well, I'll keep doing my pointless exercise then. If I'm just touching something up real quick I won't do it (and my edges touched up to a certain level of sharpness don't seem to last as long as edges freshly sharpened to that same level of sharpness), but any time I do a full sharpening I do it. Worst case it only costs me a few seconds of time, but in my personal experience I find it to give me less burring during sharpening as seen under my scope. If i get a tenacious burr with a steel that burrs badly i will cut straight into the stone to remove it and start over from scratch on my sharpening session (Smith and Wesson 440C at 54RC has done this to me a few times). Either way, if you get great results without that step keep on doing what you do, as it is pointless for you to do it. For me it really helps me to minimize burring, espescially by "sneaking up on the burr" as I spoke about in my previous post, where I check for sharpness benchmarks at each grit so I know the knife is getting as sharp as it can get before I create a burr. Any left over sharpness on the knife from before I start sharpening may mess that up. Who knows, maybe I am just wasting my time, but my method works well for me. Other people have their sharpening methods that are vastly different than mine that work well for them. If you get great edges that last a long time it doesn't really matter how you get there, but I do like hearing how others get there. I am always trying to learn and share my experiences with others to see if anyone can learn from me. No need to get into a pissing contest or insulting by calling somebody's sharpening techniques pointless. If you feel a few strokes (as in 3-5 per side with light pressure) on a new microbevel sharpening with a coarse stone completely removes all weakened or fatigued steel everytime fine, maybe it does, but in my experience I get better lasting edges by cutting straight into the stone first. To each his own, and YMMV.
Mike
Here is the reason you dont see it, and also why I dont usually have to deal with it. This issue of well used edges and the difficult to remove burrs they can form wont come up if you regularly maintain the edge and use abrasives for touch up. It becomes a noticable problem on knives that get steeled extensively between metal removal sharpenings, knives that see heavy impact, or any knife that has extensive edge rolling, like being used on a glass cutting board. Some steels are also more prone to it that others, though it seems knife specific, since there is some variety in the treatment of the same steels by different companies. It also comes up on knives that go years between sharpenings, like my mom's kitchen knives. Some went nearly 10 years before I sharpened them, and they formed a difficult to remove burr, even after I had used a 120 grit belt on a belt sander to profile the edges. I had to go back and reform the burr again after cutting straight into an India fine stone to remove it. After that, they had no problem.