What angle should I sharpen my knives at?

[Mtn Hawk]

Cliff--

Thank you for your thorough answer. You brought up some points I probably never would have known about or figured out but I think are very important to know and understand. Your info will save me a lot of problems in the future.

DGG--

I think your advice is good. The Sharpmaker, my favorite sharpening device, is set up this way. But I wanted to learn how to freehand sharpen since most of my knife use is in the wilderness where I carry everything in and have to limit the weight and bulk. Plus, I used to watch my Dad freehand sharpen as a boy and always wanted to become proficient at it. I think it's a good skill to know.

After a lot of time, and trial and error, trying to learn to freehand sharpen I read The Razor Edge Book Of Sharpening and went with Juranitch's method. I'm still open to learning new things but have not yet found a better or more simple and time-tested way to sharpen, and I always get good results. He advises holding the abrasive at as low an angle as possible when relief grinding, the most important part of sharpening. Since each knife is different and I don't have a tool to measure angles, I don't know what angle this is, but I'd guess it's around 20-24 degrees, inclusive. Maybe it's even less.

I believe in using as thin an edge as possible. I can't imagine a situation where a thick edge outperforms a thin one, given the obvious necessity of making it thick enough to avoid rolling and chipping. The problem becomes determining this angle depending on what the knife will be used for but I think a high-quality knife should be able to handle tough tasks like chopping and batoning at a fairly low relief grind angle and 30-40 microbevel.

 

[Cliff Stamp]

I can't imagine a situation where a thick edge outperforms a thin one ...

For chopping there is an issue of binding so the absolutely thinnest edge may give high penetration but stick too badly, it depends on the wood type significantly, this is why axes used to cut softer woods have thicker profiles. You can see some effects like this in just cutting some materials where a certain amount of wedging action induces the material to split and open up, often though you can decrease the binding by use of hollow grinds as well. But generally these are secondary concerns and the effects are fairly minor compared to the adjusting from thinning most edge profiles.

-Cliff

 

[Mtn Hawk]

Cliff--

Thanks for the additional info.

I rarely chop soft or green wood so fortunately can eliminate binding as a potential problem area. What I deal with is the opposite. The dead wood in this area is so hard, dry, and dense that it's almost like chopping a rock. When I decided to switch from a hatchet to a big chopping knife I emailed Swamp Rat explaining the conditions and asked them if they thought the Battle Rat could handle it.

The BR did fine with the thick convex factory edge but I had some major doubts it could chop wood this hard with a substantially thinned-out edge. As I mentioned, I'm going to do a few more hours of heavy chopping with the reprofiled blade before I have complete trust it won't roll or chip on a long wilderness trip. Your info in this thread and others has helped me to have the confidence that I did the right thing in reprofiling the knife and that the BR will do what I expect, even with considerably less metal on the edge.

 

[gwb]

This has been a very informative thread on sharpening. I have learned a lot.

I really like Cliff’s recommendation of a dual profile edge.


What angles and finish would you all recommend for my application?

I am using a Ranger RD7 for chopping green hardwood limbs, saplings, vines, brambles, etc. For heavier work, I have a Gransfors Small Forest Axe.

Secondary Bevel
Angle & Surface finish (400grit, 600 grit, 1000 girt, etc.)

Primary Bevel
Angle & Surface finish

Thanks

 

[Cliff Stamp]

If you have to cut soft woods with a hardwood profile it isn't as bad as trying to cut hard woods with a soft wood profile which is generally not productive and dangerous. If your knife does start to bind a little due to lacking profile you can reduce the force on the swing and thus work faster and lighter. In general if you don't know much about the wood is is better to optomize for slightler harder than err on the side of too soft wood. Once you get some more experience and are comfortable with the new profile you should make a post in the Busse form. Busse has more of a tactical/utility following and it would be nice to see some voices on wood working as some people have been harassing him for years to run some longer more wood craft optomized blades but the voices are rather low in number.

I am using a Ranger RD7 for chopping green hardwood limbs, saplings, vines, brambles, etc.

Limbing, if you do it carefully and either clip or notch remove the limbs is similar to felling, but still much more demanding because all the force is concentrated on a small area and this basically multiplies the pressure the blade sees during contact, it is similar to cutting knots. However if you do what most people do with heavy blades which are very powerful cuts where the blade essentially uses its weight and speed to as much break through limbs as cut them. then it is one of the most demanding things you can do with a blade.

For the final edge bevel you want it really highly polished, I would try a 15/20 bevel first, shape the edge at 15 degrees with a really coarse abrasive, knock the burr off with an intermediate grit at 1000 or similar at 17 or so degrees per side and then deburr and set the final very fine edge at 20. After you sharpen a few times and get some experience with limbing you can likely start moving the angles down, considering the knife is rather small you should be able to get close to 10/15 for your final working profile, if you are really skilled you can move down to 8/12.

That profile may sound extreme, but that is where traditional long blades (a couple of feet) for woodworking are usually ran, however at this profile level you are generally not sweep cutting at all, and make very focused cuts.

-Cliff

 

[gwb]

Thanks for the reply.

Sounds like I have some grinding to do.

I am using an EdgePro system.

 

[DGG]

I would use 40 degrees total because that's what Spyderco Sal says to do in his knife sharpening instruction DVD.

 

[Cliff Stamp]

There is no reason to do it all at once, with the edge pro you can just move down gradually, start off by just matching the existing edge profile at taking it down a 1-3 degrees each session, this prevents any extensive grinding sessions.

-Cliff