Knife won't cut paper but still seems sharp?

S

Silens

Joined
Feb 28, 2013
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I've got a Karesuando Wolf here and I've just taken it from the sheath and had a go at cutting some regular printer paper with it. It either won't cut at all or just seems to tear the paper... Yet it easily cuts my nails.

According to a guide I read in the past, to paraphrase "A knife that can cut your nails is sharp enough for most anything". I've not got weak nails, either. Mine are pretty strong. This knife still seems to do fine cutting through various woods (Birch is the only one I can name, though I know it goes through other stuff) yet it's having trouble with paper?

Could anybody explain what could be wrong to me and how I can fix it? For the record, I just sharpened it and it hardly cuts any better than pre-sharpening (Though I'm no expert at this).
 
Push cutting printer paper is my standard for all my knives. I want at least that level of sharpness. I've read here on BF to use a sharpie on the bevel, that way you know when you're actually sharpening the apex. I also use a 10x magnifier and this definitely works.
 
Silens said:
I've got a Karesuando Wolf here and I've just taken it from the sheath and had a go at cutting some regular printer paper with it. It either won't cut at all or just seems to tear the paper... Yet it easily cuts my nails.

According to a guide I read in the past, to paraphrase "A knife that can cut your nails is sharp enough for most anything". I've not got weak nails, either. Mine are pretty strong. This knife still seems to do fine cutting through various woods (Birch is the only one I can name, though I know it goes through other stuff) yet it's having trouble with paper?

Could anybody explain what could be wrong to me and how I can fix it? For the record, I just sharpened it and it hardly cuts any better than pre-sharpening (Though I'm no expert at this).
Click to expand...

You may be feeling a wire edge on the blade.

http://www.knifeart.com/sharfaqbyjoe.html
 
In my experience a wire edge will cut paper easily but break off on wood.

How are you cutting the paper? It should cut pretty easily slicing it at an angle. If you're just holding it up and trying to push cut, it's going to take a much sharper knife.
 
BURRS.

In all likelihood, you've probably got a big factory burr (or wire) on the edge. Not uncommon on production knives. If it's somewhat curled or folded to one side or the other, it won't cut paper well at all, but it can still 'grab' your fingernails, as you've found. The snagging/tearing of the paper is the best indicator of it's presence on the edge. Check the edge at multiple points, to see if it's a full-length burr/wire. If it is folded to one side, you'll likely be able to catch your fingernail on it from one side (curled toward your nail), and it'll probably slide off your fingernail from the other side (curled away from your nail).

Assuming it is a burr/wire, some refinement with stones and or strops will be needed, working it off from the side to which it's folded. If it's a heavy/thick burr, it probably won't come off by dragging through wood, in which case it'll more effectively be removed by abrading it with a stone.


David
 
Silens said:
I've got a Karesuando Wolf here and I've just taken it from the sheath and had a go at cutting some regular printer paper with it. It either won't cut at all or just seems to tear the paper... Yet it easily cuts my nails.

According to a guide I read in the past, to paraphrase "A knife that can cut your nails is sharp enough for most anything". I've not got weak nails, either. Mine are pretty strong. This knife still seems to do fine cutting through various woods (Birch is the only one I can name, though I know it goes through other stuff) yet it's having trouble with paper?

Could anybody explain what could be wrong to me and how I can fix it? For the record, I just sharpened it and it hardly cuts any better than pre-sharpening (Though I'm no expert at this).
Click to expand...

If it pares fingernails and shaves wood well but cannot do fine slicing, it possibly has an overly broad cutting edge. Lowering the inclusive angle should do wonders for it. Scandi grinds aren't known for slicing paper real well but can do a good job if worked nice and thin. From the factory, many have a slight convex on top of a microbevel - very tough and appropriate for wood working but not so good on printer paper (though will likely shave arm hair etc). Use it for a while and if it fails for your uses, consider lowering the angles on the cutting edge and ditching the microbevel. A slight freehand convex on a more acute edge is all that's needed to turn most over built Scandi edges into good EDU cutters.
 
Cuts both ways on my nail (I was reluctant to do this; almost ruined my nail polish!) so I'm guessing it's as HH said and that it's too broad. I remember it cutting paper when it came out of the box (Maybe a year ago now) though it had a polished edge at that point.

It's never been shaving sharp as far as I know, though that may have been technique and/or my hair. I opted for a scandi grind due to apparent ease of sharpening in the field compared to other grinds.
 
It's pretty hard to diagnose these things remotely, but I have some thoughts. Look straight down at the edge in strong light and rotate it around a bit, trying to get light to shine on the edge. Do you see any light reflected back? You may see it in small spots, or even just tiny flecks of light. If so, your edge isn't fully apexed in those areas.

If you get past that check for a rolled edge. Hold the blade, edge up, and check for sharpness with your thumb, stroking your thumb pad across the edge. NOT down the edge, but across it. You've probably done this before. You'll feel the blade bite into your thumb print and the sharper it is, the more bite you'll get. But here's the trick: Now spin the blade around so the point is facing you, but the edge is still facing up and do the thumb pad test again. Does it feel any different? Sharper, or duller? If it feels sharper one way or the other, the edge is rolled or you have a burr. Be sure to do this test at several points on the edge, from heel to tip. It may be perfect in most spots, and rolled or burred in others.

I suspect the blade is simply not apexed and you'll see that with test #1 above. But again, it's tough to be accurate about this without seeing or touching the blade. Good luck! :)

Brian.
 
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