Convex Edge Sharpening (BRK B1)...also KO work sharp question.

G

glocke12

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Apr 1, 2012
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Picked up a Bark RIver B1 recently, along with sharpening supplies (strop, sandpaper, bars of abrasive)...

I watched all the videos i could on sharpening convex blades, practiced on some cheap knives I have laying around, and than practiced some more...than once I felt I had the stropping movements down correctly I tried touching up the blade on my B1 with the leather strop and the black abrasive followed by the green abrasive.

Fail...ended up with a blade that was not sharp and was actually more dull than it was previously...

After working with the 1000 grit paper and the black and green abrasive for a bit once more, I was able to bring an edge back (probably not the original profile), but I am still clearly doing something wrong. The first third of the blade (going from the tip backwards) is very sharp, sharp enough to shave arm hair with..middle of the blade is almost as sharp, but the back end of the blade is just not that sharp.

Any thoughts? Should I just stop buying nice things?

Also, a friend has the Ken Onion Work Sharp...He's offered to bring it over to my place to sharpen some of my kitchen knives...If I wanted him to put a convex edge on some of my less expensive knives, where should the guide be set? 15 dg? 20 dg? Would it be advisable to use this tool on my B1?
 
How strong would you rate the downward pressure you're applying? Too hard and you create an abrasive surface area that follows the edge dulling it.
 
B34NS said:
How strong would you rate the downward pressure you're applying? Too hard and you create an abrasive surface area that follows the edge dulling it.
Click to expand...

I'm trying to keep the pressure no heavier than what I would shave with...

Other thing I was thinking is that the blade angle I was using is not correct. A couple of videos said to keep it at 13-15 dg, and I am pretty sure I've kept to that, even used a protractor to verify.
 
Regarding stropping angle, I learned a really excellent way to gauge this a while back. Start with the blade on the stop way lower than you think it should be. Now move the blade *forward* so the edge would cut into the strop if you raised it. Now, slowly raise the spine of the blade, as you move it forward, until you feel the edge *just* bite into the strop. Stop! That's the angle you should be stropping at. Obviously the stropping should be done edge trailing. We're only use edge leading as a test to find the right angle.

For the WSKO, the "convex" thing is really overstated. It makes a slightly convex edge bevel, but I don't think it's much different than a normal edge done on a stone. It's very, very close; there's really no easily discernible difference. What angle to use on your kitchen knives? between 15 and 20 degrees is about right. Personally I try to stay close to the factory edge angle as a starting point, but I do it all freehand. I don't use the edge guide. The WSKO can put some pretty impressive edges on kitchen knives.

Brian.
 
Agreed - light pressure and using the trick bgentry mentions to determine getting to the edge of the edge. More pressure even at the angle determined using the above trick and you go past it rounding it off.

I use linen belts on the WS including the KO with CBN on Bark River knives. Use edge trailing only strokes on the KO with linen belts and you can go to 1/2 micron if you like although a 4 micron finish will exceed the black compound level of finish.

Just use the KO without angle guides for this.

---
Ken
 
I found some very good YouTube videos on sharpening a convex blade.
I have a Bark River DPH.
The easiest way to "round" the edge is by applying too much pressure when sharpening/stropping.
Practice your form.

I use a variety of wet/dry sand papers on a piece of that rubber drawer liner stuff...it has just enough give but is thin enough to not give too much and round the edge. I also spent time practicing how much/little pressure is needed to sharpen/strop on the liner material and my leather strop with black/green compounds.

Don't give up. Continue to work on the knife until you begin to get a sharp edge then work closely to develop the muscle memory and gain experience with the angle you hold the edge to the surface and the amount of pressure needed.
 
You also might have a micro bevel issue. I know Bark River does excellent convex grinds, but my Gameskeeper in A2 came with a micro bevel. I touched it up on a Norton waterstone and stroped it back to a great edge.
 
If the tip and belly are good, I'd be taking a close look at the edge for the presence of a slight recurve along the heel/straight portion. Many belt sharpened edges come with one, intentional or no, and it can cause issues with making a good edge in that area if not taken into account. Pretty sure my Bravo Necker 2 came with a slight one I've since ground away over time.
 
glocke12 said:
I'm trying to keep the pressure no heavier than what I would shave with...

Other thing I was thinking is that the blade angle I was using is not correct. A couple of videos said to keep it at 13-15 dg, and I am pretty sure I've kept to that, even used a protractor to verify.
Click to expand...

To be fair, depending on the blade geometry and steel composition that might even be "too much". When I was first learning the profile I had more issues when figuring out the correct motion and specific pressure for certain parts of the blade. The best advice I'd received was to treat the blade geometry more like a lens in optics than the more harsh angles for purely inclined planes. Start out with no pressure at all, slightly increase your pressure until you begin to feel and see results. You can always add more downward pressure incrementally, but too much and it will dull the blade or even round the tip off. Always draw the material towards the top (away from the edge)of the blade first to build the shape of your "lens" instead of focusing on getting the lesser (edge) material aligned, you'll get to that part after you've established some general symmetry. Just Remember, very, very, light. Sandpaper in various grits/stages on a strop or mousepad works brilliantly for helping to sculpt the profile. Take you're time and have fun! :thumbup:
 
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