How To Worksharp BGA knife not cutting paper

B

Bo-dacious

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Aug 13, 2016
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Hey guys, I have a question about my knife not cutting paper. I'm using a work sharp blade grinding attatchment and I get the knife seemingly very sharp to where I cut myself if I tap the edge. However, the knife tears the paper when I cut it. I know paper slicing isn't the best way to test sharpness, but it's the way that makes the most sense to me until now? Is it possible that my knife is really sharp, yet won't cut paper? Is my knife not actually that sharp? And howcome when ever I use the worksharp BGA, the knife won't cut paper, but for the original attatchment, or stones, it cuts paper fine? Can anyone help?

Thanks,

Bo
 
I have the BGA and it has a big tendency to flip burrs because it cuts so fast. Do you finish on the 12k belt? Use very very light finishing passes and flip the blade. It should be very sharp after the tinfoil edge is removed.
 
I go up to 12000 grit and there is no burr. But my question is: can the knife be really sharp even though it doesn't cut paper? Like could it be a different reason that it's not cutting paper? It seems SO sharp. Cuts meat like a dream. Maybe I'm getting hung up on this paper thing but I really want to know.

Bo
 
Try turning the paper 90 degrees. The grain can be a bitch. Otherwise no, a sharp refined edge should slice paper (or at least cut into it)
 
Bo-dacious said:
I go up to 12000 grit and there is no burr. But my question is: can the knife be really sharp even though it doesn't cut paper? Like could it be a different reason that it's not cutting paper? It seems SO sharp. Cuts meat like a dream. Maybe I'm getting hung up on this paper thing but I really want to know.

Bo
Click to expand...
Definitely sounds like a wire edge problem. Once you come off the lower grits and transition to the finer grits after removing the scratch pattern of the previous belt try turning the speed down to the second or third lowest setting and doing the alternating very very light strokes I have found this method to work for me very well.
 
It might sound stupid, but maybe it's the paper? Do you have other knives that cut the same paper better? Just saying that there is a big difference between really cheap printer paper and glossy magazine print paper.
 
What I think the problem is there’s not a bur that can be felt on one side or the other. Its a wire edge at the apex. Wire edges are very sharp. Sharp enough to easily slice open your finger. But they’re rough and jagged and will not smoothly slice paper at all.
 
In case of a wire edge: The murray carter method is pulling the edge through a block of wood a few times.
 
Agree with what 115italian said. Paper is 1st thing I test edges on but always test on cardboard/cloth too since that's what I'm primarily cutting into, if doesn't zip through those like laser, the edge is to fine/polished for my liking and go for a more toothier one.
 
Possibly the full edge has not reached a true apex yet. When you get a knife from the factory, chances are they were sharpened on a belt sander and the plane of the edge bevel can waver/wobble even slightly, which then means all the sharpening you are doing helps to flatten out those wavers but until you get them all out, the very very very final edge where one side meets the other, has not happened yet. Once it does, then things will even out and your blade will cut true, one quick test to see if things have gotten to the apex is pushing the edge against the edge of paper, if the knife goes into the paper then you have a very acute apex, if not, then it is not there yet.

I find this all to often and it takes a lot of time to get to square one on the main bevels. It will feel sharp, grabby, but really doesn't cut well until you have reached that.

The way I can see this is holding the blade up towards a ceiling light and letting the light play down the side of the bevel, as you tilt the blade left to right, very slightly, you can see if there are any small facets along the very edge that make their own reflection, those are the spots that have not reached the apex, so they are in a valley of sorts and will take time to get that entire bevel into one single plane.

Key is to not give up, but of course, if you waver in your sharpening method, you could be doing this forever. Sometimes it pays to get your knife to a professional sharpener that can really get those bevels set for you and then it would be easier for you to maintain what they have done.

G2
 
I tried the paper both ways and I've tried different paper. Someone told me that it should slice the paper even with a burr, is that right?

OK, so gary w, I'm not sure I get this, what is the best way to get that apex? Or did I miss that?

I tried running the edge along a piece of wood and it's cutting better for sure, but still tears the paper sometimes. Does that tell you guys anything? Should I maybe be changing to a steeper angle to hit that apex?

Thanks for the help, guys!
 
it is a hard thing to describe without photos and the knives I have right now have already had their bevels set into a single plane. I use the Worksharp Blade grinder mainly for kitchen knives when I help people from work, my folders I hand sharpen in small sharpening stones, progressing from 120 grit up to 8k Shapton stone and final strop.

Here is a quickly made diagram showing the section of the edge bevel that is 'sunk' lower than the rest of the edge bevel, until you have gotten the entire length of the edge bevel in the same plane, you will have a rough patch of edge that will feel sharp, but does not cut very well

Edge by GaryWGraley, on Flickr

One way of seeing that is the magic marker trick, mark the edge bevel with magic marker, then start to sharpen it and see if you can spot any black marker spots that were not removed, those would be the sections that are deeper and you need to work the bevel down to that level.

G2
 
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Oh ok I get it. Thanks Gary w, I'll try that next time.

When dragging the edge across wood to remove the wire edge, is harder or softer wood best?

Thanks,

Bo
 
I haven't had problems getting good sharp edges with the BGA. I usually finish on crock sticks and then a small strop or just the strop, depending on whether I want a micro bevel or not. However, just the other day I finally decided to try a leather belt on the BGA (purchased from ebay and comes with a small block of compound) and it makes quite a difference. I use it at the lowest speed setting and just barely allow the bevels to touch it as I draw the blade across. It rips off any remaining burr/wire quickly and easily and leaves an edge that glides through paper. The belt and compound were about $19 shipped. :thumbsup:

wskobga.jpg
 
I don't know if there is a second page of posts. I don't know where to look for that, but I responded to everyone and. Thanked you guys for helping, I just can't see that post.

Bo
 
Thanks, g Scott, I have stropped my blades and it doesn't seem to make a difference. I have no idea what the problem is. I do everything you guys say I copy the videos exactly and it won't work. I should note that I had my dad try on my worksharp and he couldn't get it that sharp either, and he's a machinist/milwrite/welder so he knows about steels and angles and pressure and stuff like that.

Thanks guys,

Bo
 
I should also note that when I tried it on a scandi grind knife and on the clip of a machete I'm modding, it worked a lot better. I have no idea why that is the way it is. Any ideas?

Thanks,

Bo
 
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