Frustrating Edge

danseifert · Jul 30, 2011

I'm currently working with an edge that I cant get to a satisfactory level of sharpness. I'm not looking for a crazy hair splitting edge, just a razor sharp edge that I can maintain for awhile. The knife is a Bradley Alias 2 with an S30V blade. I'm sharpening on a Spyderco sharpmaker at the 40 degree setting on the coarse and fine stones that come with the sharpmaker.

I keep ending up with an edge that will shave hair with little effort but cannot cut slice paper at all. Not sure what I'm doing wrong. Could my edge be rolled or have a burr causing it to vary in performance depending on the cutting medium or materials?

I have never been able to sharpen Benchmades. Should I do a back bevel on the sharpmaker and then hit the edge at 40 degrees? I hesitate because I dont want to buy any diamond stones and also don't want to work the knife on the sharpmaker for 6 hours to remove enough metal to reprofile it. I'm hoping there is something wrong with my technique or you guys might have a tip or two.

Why cant all knives just be sharpened like a spyderco??????

rpttrsn · Jul 30, 2011

Have you first marked your edge with a sharpie? Next use the sharpmaker like you normally do and after a few strokes on each side examine the edge to see where you are making contact. It's best to use a magnifier at this time to get a better picture. Since you did not mention this I am assuming you have not done so. S30V can take quite a bit of time on a sharpmaker which in my opinion is great to touch up the same angle as the sharpmaker is set for.
Different grit emory can be wrapped on the ceramic rods to assist in re profiling the edge to match the sharpmaker angle. This will make the process quicker. Let us know what you find after the sharpie's ink has been tried.

phatboa · Jul 31, 2011

OK, I will give this a try but I am warning you I am a better hands on, in person instructor as opposed to teaching while typing.

For starters go this link http://www.emersonknives.com/ekEK_Sharpening.php. My buddy Ernie shows you the main key to knife sharpening in photo with the yellow arrows and this wording. (When you feel a burr with the back of your fingernail by running your fingernail off the edge in the direction of the arrow, you have sharpened the front edge enough. The burr develops on the side that is not making contact with the stone.

I have owned about every type of sharpener on the planet and none of the instructions ever mention that you must have the burr Ernie mentions all the way down one side before you sharpen the other side. Granted Ernie has his chisel grind so he does not burr both sides.

So no matter what type of sharpener you have, manual or electric, get the burr running all the way down one side before you change to the other side. Do not make a pass on one side then switch to the other side. Also, if you are having trouble getting the burr all the way down one side, change to the other side and see if you can get the burr all along that side. Afterwards move back to the other side.

You also mentioned the back bevel. Most people are unaware that there are two angles involved, the back bevel and the primary edge. The angle does not really matter (15, 20, 30, or 40 degrees). What matters is getting the burr all along one side, then move to the other side and get the burr all along it. Then change back to the other side, get the burr again. After the burr has run down both sides then move to the strop.

If the primary edge has been sharpened a lot you will need to work on the back bevel some but not a lot. As long as the back bevel and the primary edge are apart is key. If not the blade edge area is too wide and it will not sharpen.

You should now be able to sharpen a knife on a rock or whatever now that you know about the burr line.

Phatboa <><

Noctis3880 · Jul 31, 2011

Benchmade knives are typically profiled at 25 degrees per side, so the Sharpmaker won't even touch the very edge. I would buy some P60 green paintstripper sandpaper and clamp those to your sharpmaker rods with the small binder clips.

I also find it curious how some edges can shave hair easily, yet can't slice paper for the life of me. I find it helps to check for a burr before moving from one side to the other, and between grits as well(though it's understandably more difficult at finer grits, the more you can do it, the sharper the edge).

Noctis3880 · Jul 31, 2011

phatboa said:
You also mentioned the back bevel. Most people are unaware that there are two angles involved, the back bevel and the primary edge. The angle does not really matter (15, 20, 30, or 40 degrees).

Umm, yes it does.

An excellent example would be when I sharpened my Katana incorrectly like a knife(with a bevel instead of the entire lower portion of the blade). The result was an edge that was closer to 40-45 degrees per side. When you think about it, 45 degrees per side would add up to 90 degrees, a right angle. That is the angle of a corner of a square. Now if you take a square shaped piece of steel and tried to cut with one corner, you're not going to have much luck with that.

So ultimately, edge angle matters quite a bit. You just need to find the right one for you that gives the best mix of sharpness and edge toughness, and I find 15-20 degrees will cover most of what you need.

eccvets · Jul 31, 2011

danseifert said:
I keep ending up with an edge that will shave hair with little effort but cannot cut slice paper at all.

what kinda hair are you shaving and can you do it with both sides of the blade? what kinda paper are we talking about here? will the edge catch on your finger nail? both sides?

danseifert · Jul 31, 2011

eccvets said:
what kinda hair are you shaving and can you do it with both sides of the blade? what kinda paper are we talking about here? will the edge catch on your finger nail? both sides?

this is an interesting question. It will shave the hair on both my arm and leg, but only when I'm holding my knife with my right hand and pushing away. It cannot shave hair with a draw cut at all...does this mean my edge is uneven? It struggles with any kind of paper - thin or thicker stocks. Gets through cardboard ok but with lots of pressure.

richard j · Jul 31, 2011

if you are having a hard time findint the burr, take a sharp sewing needle and run it down to the edge. if there is a burr the needle will catch. put some thread on the needle and hold it by the thread to make it more sensitive.

pwet · Jul 31, 2011

danseifert said:
this is an interesting question. It will shave the hair on both my arm and leg, but only when I'm holding my knife with my right hand and pushing away. It cannot shave hair with a draw cut at all...does this mean my edge is uneven? It struggles with any kind of paper - thin or thicker stocks. Gets through cardboard ok but with lots of pressure.

so your first assumption was right you either have a burr or have rolled the edge on the ceramics.

if you can't detect the burr yet there's one simple way to see if both sides meet. see what direction it shaves, make a couple of strokes on one side shave again, make a couple of strokes on the other side shave again if the knife still behaves the same there's a side that is not apexed.

if both bevel were clean you should move the burr from side to side with a couple of strokes and change the side of the that shaves, if that makes sense.