What Makes A Knife Sharp - Expert Advice

T

TaintedWisdom

Joined
Nov 20, 2012
Messages
13
Hi,
I recently bought a Tops Pathfinder Knife only to be very disappointed at how bad it carved into wood. By carving I mean how is able to make a featherstick or just remove some wood from a branch. I thought it must have been shipped dull and I brought it to a professional knife sharpener who put an edge on it. When I tested it again, while sharper it still isn't able to carve well into wood.

I got a much cheaper Schrade SCHF9 which carves into the same wood and spot like butter.

The knife specifications are:

Tops Pathfinder Knife
O/A Length: 9 1/4"
Blade Length: 4"
Thickness: 3/16"
Steel: 1095 High Carbon RC 56-58
Handle: "RMT" Black Linen Micarta

Schrade SCHF9
6.4" blade, 5.6" handle
1095 High Carbon Steel
Kraton handle

I've always heard the thicker the blade the less is able to carve or make a featherstick but the Schrade is 1/4 inch while the tops is only 3/16 inch.

Could someone tell me what is going on here. I spent $140+ dollars for a knife that can't even do what a $30 dollar knife does.

Lets keep this thread informative and educational, not a rant on companies if possible.

Thank You, lets see what you experts have to say.
 
Well the thickness posted on the knives is the max thickness at the spine of the knife. Depending on how the main grind is being established, you may have a thick or somewhat thin geometry behind the edge.

Not to mention that the primary bevel that actually serves as the "cutting" portion of the knife may be at an obtuse angle that doesn't want to dig into the wood.

Ultimately, you'll want to compare the geometry of the edge and behind it to determine whether or not it is acute/thin enough to dig into material. If you want the Tops knife to perform better for whittling, then you'll want to reprofile and thin out the material at the edge.
 
Does it require thinning out the knife from above the edge, say 1 inch above it or only thinning the edge itself?

I was thinking of getting someone to give it a scandi grind? Is that the same?

Thanks.
 
It doesn't matter what the knife costs. What matters in the task you are undertaking is called Edge Geometry. What is the total inclusive angle of each knife? Is it 60 degrees? Or maybe 40 degrees? That is the difference in what makes one knife excell more than the other.
 
you would need to look at a few things.

primary grind type
primary grind angle
thickness at the transition from primary to edge grind
edge grind angle

The Pathfinder looks to have a pretty shallow primary grind, and I don't think TOPS takes the grind very thin before sharpening. Also, the edge grind is likely also pretty obtuse. You can refine the edge a lot without changing the angle, so the apex would be very fine, but with the heavy grind angles and thick steel, the force you apply in a cut is mostly used to wedge the blade, not to cut at the edge. The way to 'fix' it is to reduce the angles at the edge and perhaps the primary grind (this would remove a lot of blade coating) and to make the knife thinner in cross section as well.
 
Great question. I noticed my "expensive" knives could chop all day and still slice right though paper after it but could not make a darn feather stick. I had to use a Rat 1 and later my Ritter Griptilian to make a feather stick. The explanations above were very helpful. I won't be buying anymore "expensive" knives until my "cheap" knives die or get lost or the company that makes the expensive ones, starts sharpening to suit my outdoor needs.

Unklfranco
 
TaintedWisdom got a lot of good answers to his question. Edge geometry is important, fundamental to knife design, and often poorly understood. A blade that is properly hard and very thin behind the edge (that is, behind the sharpening bevel) will outcut an identical knife with the same angles that is thick behind the edge. The trade off for this performance is lower resistance to lateral loads than the thicker-edged blade. The thinner blade is also much easier to keep sharp because so little metal has to be removed from the tiny sharpening bevel.
 
Thanks for all the great replies. It looks like I will have to thin out the knife and give it a scandi grind. I'm bringing it to a sharpening shop in an hour, lets see how it goes when I get it back. I was debating between keeping that way and getting a mora for feather sticks but a small knife like the Tops Pathfinder should be able to do a feather stick, is why I got it. I won't be bottoming much with it and epic I did thinning out the knife shouldn't cause it to break when splitting small branches. Very disappointed as I was going to buy an Esee 4 which was much cheaper than the Tops Pathfinder and now I need to invest much more getting it shaped and sharpened.
 
unklfranco said:
Great question. I noticed my "expensive" knives could chop all day and still slice right though paper after it but could not make a darn feather stick. I had to use a Rat 1 and later my Ritter Griptilian to make a feather stick. The explanations above were very helpful. I won't be buying anymore "expensive" knives until my "cheap" knives die or get lost or the company that makes the expensive ones, starts sharpening to suit my outdoor needs.

Unklfranco
Click to expand...

Yep. I've gotten plenty of spendy and highly recommended knives only to find they don't carve worth a squat. The mora spanks every one of them.

To the OP, you're not necessarily looking for a scandi grind and I'm not even sure it can be done on the knife you refer to. What everyone is saying is that the edge is too thick. Meaning it's either ground at an obtuse angle or more likely, where the edge bevel and the primary bevel meet is too thick. Knives like tops, swamp rat, scrapyard, esee, becker, etc are made for the lowest common denominator. The guy who wants to beat it through a concrete block. In order to do that they make knives that are overly thick in the edge. My guess is you just need to thin the edge a bit. I have a scrapyard 711 that makes fuzz sticks just fine but that was after I sent it to Scott Gossman to fix the edge. It was a froe from the factory, now it's a knife.
 
You can't make it a scandi because it is already ground with a regular primary. If you ground it to where the current primary grind ran to the cutting edge, you would have a low angle zero grind, and the edge would cut like fire, but be very delicate.
 
I should have visited this site before buying the knife but didn't because I didn't think people would be very helpful. I've dropped a lot of money on the knife and now I brought it to a knife shop to see if they can do something about it. They say it should be done by Friday, lets see if it can at least carve a bit better and isn't at the expense of weakening the knife by a lot. I should have gone with an Esee 4 or just that Schrade and a Mora for making fire sticks. At least with the Schrade I could batton all I want with it and hack with it without worrying if it would break on me because with that 1/4 inch steel it would hold much better. Now I got a knife at I need to modify a lot at my own expense and it might not even be as good as a $30 dollar knife. I know one knife can't do it all but a small 4 inch knife like that isn't going to batton well and with that grind and shaped is not carving at all, just slides down the branch. It can't do neither well, very disappointed. If after this modification it doesn't carve or make a fire stick well I will just cut my loses, throw it around the house and buy a Schrade and a Mora, with less than $45 bucks I got more knife than a $200.
 
You must log in or register to reply here.
Back
Top