I have been reading where really course edges can also be really sharp, and have experienced this myself, but I cant duplicate it reliably. I tried a chef's knife from Faberware, and got an edge that could cleanly slice a plastic grocery bag down the side, but it would not shave hair all that well. This came from an 800 grit waterstone from the local woodworking shop. I've emailed Cliff about it, but wanted to get some other opinions as well. I use an 805 TSEK from Benchmade for EDC and like this kind of edge on it. Is it possible that when trying to cut off the burr, using alternating strokes, that the 800 is course enough to create another in just one pass? I'm using a 17 degree bevel with a 22 degree angle to cut off the burr. Also, hardly any of my knives can push cut newpaper or typing paper at 90 degrees to the edge, but they can shave and cut hair held between my fingers. Is it my paper holding technique, or my sharpening technique that's causing the problem?
-
The BladeForums.com 2024 Traditional Knife is ready to order! See this thread for details: https://www.bladeforums.com/threads/bladeforums-2024-traditional-knife.2003187/
Price is$300$250 ea (shipped within CONUS). If you live outside the US, I will contact you after your order for extra shipping charges.
Order here: https://www.bladeforums.com/help/2024-traditional/ - Order as many as you like, we have plenty.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Need Help With Course Grit Sharpening
- Thread starter me2
- Start date
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Yes, really coarse stones can create a burr in one pass, that isn't likely the problem though, it is most likely an angle and/or pressure problem. This is assuming the bevels are ground fully and meet at strong steel under the burr. The easiest method is to sharpen until you have a full even burr on one side because then you know exactly how to proceed. With really coarse edges you can see all the details even under light magnification. As the burrs are folded over they will show as very dark bands along the edge, they will also be much more jagged than the finish of the stone as they are cracked/fractured in pieces.
With a full burr visible, which is usually the case by eye on really coarse stones depending on the steel (check under magnification to make sure as otherwise you are running basically blind), use few short strokes on the stone, alternating sides to remove the burr. The burr either comes off or is folded almost immediately on the stone so long strokes are not productive. The trick is finding the minimum pressure which enables the burr to be cut off, too much and it folds, too little and it bends it as well as it won't cut it. You also need a much larger angle. You should be able to feel the burr being cut off, it bites strongly into the stone.
Here is one of the "tricks", if the first few passes at the high angle don't remove the burr, you can't continue to use them, this then is the same thing as not increasing the angle in the first place. You have to reduce the angle, recut the edge to the primary and then remove the burr again. You also want to use the minimal amount of passes to remove the burr as otherwise you thicken the edge and risk just creating it again. On cheap stones this may be as much as five per side, on really nice aggressive ones it is usually 1-2 per side.
http://i7.photobucket.com/albums/y269/CliffStamp/phil wilson/south fork/south_fork_hardware_fine.jpg
That is a South Fork, S30V, 60 HRC, ~15 included, with the fine side of a cheap hardware store hone, push cut on newsprint. At that distance, the CRK&T M16-14's were still slicing the paper after the mountain of cardboard cut recently showing the insane ability of coarse edges to give aggressive slicing edge retention.
-Cliff
With a full burr visible, which is usually the case by eye on really coarse stones depending on the steel (check under magnification to make sure as otherwise you are running basically blind), use few short strokes on the stone, alternating sides to remove the burr. The burr either comes off or is folded almost immediately on the stone so long strokes are not productive. The trick is finding the minimum pressure which enables the burr to be cut off, too much and it folds, too little and it bends it as well as it won't cut it. You also need a much larger angle. You should be able to feel the burr being cut off, it bites strongly into the stone.
Here is one of the "tricks", if the first few passes at the high angle don't remove the burr, you can't continue to use them, this then is the same thing as not increasing the angle in the first place. You have to reduce the angle, recut the edge to the primary and then remove the burr again. You also want to use the minimal amount of passes to remove the burr as otherwise you thicken the edge and risk just creating it again. On cheap stones this may be as much as five per side, on really nice aggressive ones it is usually 1-2 per side.
http://i7.photobucket.com/albums/y269/CliffStamp/phil wilson/south fork/south_fork_hardware_fine.jpg
That is a South Fork, S30V, 60 HRC, ~15 included, with the fine side of a cheap hardware store hone, push cut on newsprint. At that distance, the CRK&T M16-14's were still slicing the paper after the mountain of cardboard cut recently showing the insane ability of coarse edges to give aggressive slicing edge retention.
-Cliff
You may have something with the recutting of the edges. I'll try that a time or two and see what happens. Also, I may try some sandpaper instead of stones, as I vaguely remember getting a 220 grit edge to shave w/o too much trouble off of some wet/dry paper. I can sometimes feel the burr being cut off on the stone, and it sounds different as well. After cutting the burr off at the higher angle, do you go back and remove the microbevel with a few strokes? Also, both have been backbeveled on a 1x30 sander, so I may have heated the edge.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
I used to recut the edge but stopped because there is too much chance of just creating the burr again. I have measured the cutting ability, sharpness and edge retention with the final more obtuse micro-bevel and don't think it is a drawback.
You can actually get away with just using a larger angle on one side which I found out recently sharpening chisel ground blades, which should be obvious because chisels are usually lapped flat, but there is no reason that the same technique can't be extended to v-ground edges. It is much harder to do though.
If the knives were overheated and the temper drawn then it will be very difficult to remove the burr as the steel could be significantly softened. Generally though this is pretty hard to do unless you are grinding really thin edges as otherwise the blade will heat sink rapidly.
Sandpaper generally behaves as a freshly lapped stone, so if sandpaper succeeds and the hone does not it might point towards a non-flat stone, or irregularites in the finish/composition. Generally those the latter has to be horrible to actually prevent sharpening.
-Cliff
You can actually get away with just using a larger angle on one side which I found out recently sharpening chisel ground blades, which should be obvious because chisels are usually lapped flat, but there is no reason that the same technique can't be extended to v-ground edges. It is much harder to do though.
If the knives were overheated and the temper drawn then it will be very difficult to remove the burr as the steel could be significantly softened. Generally though this is pretty hard to do unless you are grinding really thin edges as otherwise the blade will heat sink rapidly.
Sandpaper generally behaves as a freshly lapped stone, so if sandpaper succeeds and the hone does not it might point towards a non-flat stone, or irregularites in the finish/composition. Generally those the latter has to be horrible to actually prevent sharpening.
-Cliff
The Camillus is full flat on 3/32 stock, 2 inches wide and the edge is very thin. I tried some Aluminum Oxide P100 grit sandpaper on the 805, and found something interesting. The grit seems to be high enough in some places that one grain or 2 actually impact the edge directly and prevent the blade from moving forward during the stroke. It feels as though the edge is sliding along one grain, just like trying to cut it. This could obviously lead to sharpening trouble. I checked the 805 at 60x with the pocket microscope and there were large dips in the edge that looked like a small cookie cutter had just been used. I sharpened the Camillus again with the 800 grit waterstone, and it seems to have improved. I had a good burr all along the edge, and could definately feel it bite into the stone while removing it, or just switching sides in general. I'll probably do it one or 2 more times to see if it improves further. It was a second because the handle was cracked, so I got it for $3, but there's no certainty that it was even hardened since it was a reject. I did a little experiment about 3 months ago and found that on the same knives, with the same angles, the 800x waterstone cuts faster than the coarse side of my coarse/fine India stone.
Speaking of forming burrs while grinding. I have been working on 2 knives made from unsoftened files, and noticed the areas where the steel was left soft near the tang form a burr that looks like a piece of foil hanging off the blade, while the fully hardened parts form a tiny burr that I'm barely able to feel, let alone see. I overheated part of one, turning it blue while grinding, and the same large burr formed there while grinding it away, but stopped as soon as I ground past the yellow/straw colored section. It just seems that no matter how much I grind, the burrs in the hardened sections dont get any bigger, unless I over heat the area and soften it.
Ok, 2 things. One, I just cut myself for the first time in months while using a knife.
Second, I noticed the scratch pattern on my Faberware chef's knife was at about 45 degrees to the edge under magnification. This is no doubt due to using a hone that is slightly shorter than my blade. Would this make any difference? In an attempt to get rid of them, I started doing small circles up and down the edge. This, for the first time, allowed push cut into advertizing paper at 90 degrees to the paper edge about 1" from the grip point. I was under the impression that this was an inferior way to sharpen, and was mainly using it to remove some material to thin the edge some more.
Second, I noticed the scratch pattern on my Faberware chef's knife was at about 45 degrees to the edge under magnification. This is no doubt due to using a hone that is slightly shorter than my blade. Would this make any difference? In an attempt to get rid of them, I started doing small circles up and down the edge. This, for the first time, allowed push cut into advertizing paper at 90 degrees to the paper edge about 1" from the grip point. I was under the impression that this was an inferior way to sharpen, and was mainly using it to remove some material to thin the edge some more.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
me2 said:The grit seems to be high enough in some places that one grain or 2 actually impact the edge directly and prevent the blade from moving forward during the stroke.
The ez-lap diamond plates are like this initially, really clumpy, some cheap stones can also do with a lapping before they hone evenly otherwise in places they will smash into an edge rather than cut it cleanly.
me2 said:...a piece of foil hanging off the blade
Soft stainless usually produce a small burr just like you describe, on machetes it can be so large it is a fraction of an inch wide when they are filed. However I recently sharpened a 420HC chef's knife by Wilson and it didn't form a burr at all, even when checked under mag, it was trivial to sharpen, one of the best blades I have handled in a long time for sharpening. Both steel and heat treatment make a large difference.
[circles]
me2 said:I was under the impression that this was an inferior way to sharpen, and was mainly using it to remove some material to thin the edge some more.
Generally it doesn't leave an optimal scratch pattern with coarse abrasives because it runs scratches along the edge which weakens it, plus it won't produce the same micro-teeth that scratches that sharpening into the edge does. However if you can remove a burr more effectively that way it is likely better because burr'ed edges are tremendously weak. It could simply be an issue of pressure or angle control.
-Cliff
Cliff--Cliff Stamp said:[circles]
Generally it doesn't leave an optimal scratch pattern with coarse abrasives because it runs scratches along the edge which weakens it, plus it won't produce the same micro-teeth that scratches that sharpening into the edge does.
I have been using small circles with the abrasive for the relief grind as this seems to work quicker than any other movement, then sharpening into the edge for the microbevel. Are you saying that small circles should not be used for either the relief grind or microbevel, or just not used for the microbevel?
Thank you.
Cliff Stamp
BANNED
- Joined
- Oct 5, 1998
- Messages
- 17,562
Generally it doesn't matter what you use for the shaping unless you leave that as your final finish. If you use an x-coarse hone to set the edge at 10 degrees grinding parallel to the edge and then just jump right to a micro-bevel at 15 which is then maybe only 0.1 mm wide, the edge could fold along the deep scratches running parallel to the edge above the micro-bevel.
It depends on what you can cutting and the strength of the steel. It is more of a factor on really low angles because then the x-coarse scratches will cut a significant depth fraction wise into the edge above the microbevel. You won't see much significance at obtuse angles because the edge is too thick to fold unless you are chopping, there is then the factor of extra friction because the grind lines are perpendicular to the cutting action of the blade.
Some axe honing does recommend sharpening with circles, the hones are even circular, however most will also tend to recommend going to a very fine polish, finishing usually on loaded leather and thus any scratches are long since polished away. You can feel the difference the orientation of the scratches make on cutting ability because they control the angle of the teeth. If you cut into a blade on a 45 you can make the teeth point back towards the handle or towards the tip, so it will slice really aggressively one way or the other. If the blade is at a 90 it will be aggressive both ways.
-Cliff
It depends on what you can cutting and the strength of the steel. It is more of a factor on really low angles because then the x-coarse scratches will cut a significant depth fraction wise into the edge above the microbevel. You won't see much significance at obtuse angles because the edge is too thick to fold unless you are chopping, there is then the factor of extra friction because the grind lines are perpendicular to the cutting action of the blade.
Some axe honing does recommend sharpening with circles, the hones are even circular, however most will also tend to recommend going to a very fine polish, finishing usually on loaded leather and thus any scratches are long since polished away. You can feel the difference the orientation of the scratches make on cutting ability because they control the angle of the teeth. If you cut into a blade on a 45 you can make the teeth point back towards the handle or towards the tip, so it will slice really aggressively one way or the other. If the blade is at a 90 it will be aggressive both ways.
-Cliff