What angle should I sharpen my knives at?

[troutfisher13111]

I use a lansky sharpening kit to sharpen my knives. What would be the best angle to use for my tactical knives? Thanks.

 

[HoB]

Sorry to put a damper on your enthusiasm, but "the best angle" depends on the knife, the steel and most importantly your intended use. The smaller the angle, the better the edge will cut, but only a well hardened, quality bladesteel will support very small angles. However, if you intend to use your knife as screw driver or intend to use it to baton and pry, you better keep the edge very stout. However, the width behind the edge makes a big difference too, if the width behind the edge is thick, and you want a real cutter, you better thin out the edge using a double bevel combination, where your back bevel angle is very small and your edge bevel is substantially larger (well you can keep it also small to make an even better cutter).

To give you some numbers, that are simply a personal opinion and many people would very much disagree:

If the width behind the edge is reasonably small (0.02"), I have been able to get very good cutting ability with about 12 deg per side, where I may or may not add a microbevel at 15 deg, depending how much I have to fight a burr. There are many people that would consider this as obtuse. If the edge is much thicker than this I would definitly thin out the edge first by applying (depending on the blade grind) maybe a 6-8 deg (per side) relief. For an edge that I know will be used by careless people (the rest of my family), I would apply an edge bevel of about 20 deg per side at the same width behind the edge. I may be willing to deal with something that is 0.03" for a harder user but unfortunately many edge are way too thick with 0.04" upwards.

This is all in regards to folders or kitchen knives (which are usually even thinner). For big big choppers the edges need to be more sturdy, but I don't feel qualified to give advice on that, I don't have enough experience with those. I could only repeat the recommendations that Cliff has given me.

 

[IUKE12]

I use a lansky sharpening kit to sharpen my knives. What would be the best angle to use for my tactical knives? Thanks.

Well, since you have the Lansky and are restricted to four angles I would use the 20 degree setting. It will work well for you.

 

[Dog of War]

Basically agree with HoB ..... around 12 degrees per side for the primary is an excellent place to start when you reprofile an edge, then vary the secondary or microbevel from 15-20 degrees/side depending on use and steel. This probably works for better than 90% of the knives I use, and 12 degrees/side gives very noticeable improvement in cutting ability over most factory edges.

Kitchen knives that won't be used for anything hard I'll reprofile even more acute, 10 degrees or less, but being softer steel need a more obtuse 20 microbevel. Also high hardness tool steel blades that won't get a lot of lateral stress I sometimes take down 10 degrees or less ..... although IMO the law of diminishing returns kicks in as you start taking the primary down below 10-12 degrees.

For really hard use knives if 12 degrees turns out to be too thin it's then an easy job to just reprofile part of the edge to say 15 degrees, giving a multibevel edge which still gives some performance advantages for most work over a 15 degree single bevel edge.

 

[Cliff Stamp]

Tactical knives tend to be less like knives and more like tools, what is the scope of work, what is the hardest thing the knife is likely to see and what would you like the condition to be at the end of the work? In addition what is the steel/knife?

-Cliff

 

[Mtn Hawk]

Cliff Stamp--

Since the subject of big chopping knives was mentioned, what angle do you suggest? To see what would happen, I reprofiled a SR Battle Rat and CS Trailmaster (both with rather thick factory convex edges) to about what Dog of War suggested: 12 degrees primary and 15-20 microbevel. I thought this might be too thin, but so far the BR is holding up chopping hard, dead fir and pine branches. I would estimate there is about a 50% improvement in cutting efficiency over the factory edge. The Trailmaster chipped a bit near the tip but I got the edge pretty thin there. I freehand sharpen these so don't have the option of putting on a multibevel.

Thank you.......

 

[Professional_Leo]

usualy i use the smallest angle i can on my benchgrinder. gives a very good edge but doesnt last too long on weak metal, luckly i can just go out and resharpen if needed

 

[troutfisher13111]

My knives are used for everyday use. Cutting rope, boxes, opening packages, splitting small wood,carving, cutting small branches, opening cans. Maybe a little prying. Things like that. I would like to be able to use them to defend myself if I needed to though. Most of the steels are AUS-8 and VG10.

Is there a better sharpening system for my needs than the lansky for under a $100?

Thanks guys for all your time.

 

[HoB]

Well, in order to defend yourself the knife either has to be super sharp for structural cuts or can be as blunt as a screw driver to be able to stab, so that criterium doesn't really help much. Non of your other uses are exactly demanding cutting applications. So 15/20 per side should be a good choice and not too much work. If you find out that you like a bit more cutting power, you can take it to 12/15. This way you will split up the work of reprofiling, too, since you likely going to have to reprofile unless you have mostly Spyderco knives.

I just took an RD9 to 12 deg per side with no microbevel other than an increase to 15 for the last 5 strokes on my finest stone, but that is more to give the edge the final touch rather than to microbevel. I let you know how it holds up, as I am headed for the yard now.

If you don't want to get into sharpening too much, but want some flexibility and very good edges for a resonable amount of money, I would get a protractor, a coarse or x-coarse DMT, and the Sharpmaker. The DMT together with the protractor will allow you to rip in a new edge or backbevel relatively quickly and from there you can refine the edge with the Sharpmaker at 15 or 20 deg per side. You don't have to hold the angle perfectly when you set the edge. The better you are at holding the angle the less work you have to do, but otherwise it is not important, as long as you don't let the angle creep up.

Mtn. Hawk. Sure you can do a multibevel by hand, just get a protractor to get a feeling for the angle or use some coins to lean the spine on. You don't have to get the transition of the multibevels sharp. Freehanding is likely going to round the bevels over a bit so that you actually end up with something like a convex edge, which is just as good, if not better.

 

[Mtn Hawk]

Mtn. Hawk. Sure you can do a multibevel by hand, just get a protractor to get a feeling for the angle or use some coins to lean the spine on.

Thanks. I'm sure this would work but I like to freehand sharpen as simply and quickly as possible without making too much of a fuss about it. I'll go with what you said here:

You don't have to get the transition of the multibevels sharp. Freehanding is likely going to round the bevels over a bit so that you actually end up with something like a convex edge, which is just as good, if not better.

Good point. I have seen this mentioned before but had forgotten it. Thanks for reminding me.

Actually, as I reread my question, I should have asked about the relief grind angle instead of the microbevel. Since the microbevel is so tiny and chopping impacts are so powerful, it probably doesn't make much difference what angle it is as long as it's not too small.

How much metal is behind the microbevel would be much more important. The problem becomes how to determine what angle the relief grind should be. Too small and it won't stand up to chopping forces, too large and it makes chopping harder than it has to be.

 

[Cliff Stamp]

Since the subject of big chopping knives was mentioned, what angle do you suggest?

The thinnest I have gone was 8/12 on a Battle Mistress, this would cut most woods, but the edge would turn at the level you would see visible deflection on harder knots so the edge retention was low on poor woods and you would not want to use it for any difficult batoning with that profile.

12 degrees primary and 15-20 microbevel.

20 is a little high for local woods, 15 is about optimal here. Yes you can gain a lot in chopping performance, 50% was about what I saw on the Marine Raider bowie as well. Aside from the raw penetration you also influence shock and fatigue which make a big difference in extended use.

Ironically the edge often gets more durable for wood work if you reduce it, it isn't actually stronger, but the cutting ability tends to reduce impacts and lateral loads to such an extent that the edge retention increases. Up until the point you miss the wood and hit something else anyway.

My knives are used for everyday use. Cutting rope, boxes, opening packages, splitting small wood,carving, cutting small branches, opening cans. Maybe a little prying.

The can cutting it critical, you want the final bevel to be 15/20, closer to 20 for most steels and it can't be just a micro-bevel, it needs to be about half a mm or so wide unless you are really careful and avoid lateral loads. I would recommend a 15/20 profile for that work for most stainless. You might want to run a dual profile, reduce the edge in the blade near the handle and leave it more coarse at a 10/15 profile with the 15 being a full micro-bevel (no visible width), and then run a thicker and more polished edge out near the tip for the heavier wood working and metal cutting with the 15/20 macro-bevel profile.

-Cliff

 

[Dog of War]

Glad that worked out for you, Mtn Hawk. Most factory blades especially those promoted for hard use like your BR come with edges much more obtuse than most of us need .... the difference you get not only slicing and cutting but chopping as well can be pretty amazing when you take the primary down to 12 per side.

It's pretty surprising too what a difference it can make just changing the secondary bevel or even microbevel between 15 and 20. For blades made of less expensive steels or run in the softer hardness range, say 54-57, 20 degrees can make a huge difference in how well the edge holds up. Blades of higher end steels especially run hard, 59-60+ range, can often hold up to some pretty heavy work with a 15 degree secondary or microbevel and the performance difference on many materials is very noticeable. What's great is it's easy to change as needed once you've cut the primary down like you have.

Cliff, some great explanations in your last post. Thanks.

 

[Mtn Hawk]

Cliff--

Thanks for your response to my questions. Very instructive, as always. I appreciate it.

The thinnest I have gone was 8/12 on a Battle Mistress, this would cut most woods, but the edge would turn at the level you would see visible deflection on harder knots so the edge retention was low on poor woods and you would not want to use it for any difficult batoning with that profile.

It's very interesting that you still got fairly good chopping performance with your Battle Mistress at 8/12, even though there were some restrictions. I really thought I was making a mistake taking the Battle Rat down to about 12/15 but the only way I could find out if it worked was to try it. So far I'm very happy with the results on hard, dense, dry lower branches of fir and pine. Even on dead manzanita, the hardest wood I know of around here, it's holding up. I'm going to do a few more hours of chopping with it before I am confident I can leave it at those angles but so far so good.

Yes you can gain a lot in chopping performance, 50% was about what I saw on the Marine Raider bowie as well. Aside from the raw penetration you also influence shock and fatigue which make a big difference in extended use.

Great point about increased penetration reducing shock and fatigue. This is something I don't see mentioned often but I think it's very important, especially in wilderness emergency or survival situations where wood chopping is often the most time- and energy-intensive work one does.

Ironically the edge often gets more durable for wood work if you reduce it, it isn't actually stronger, but the cutting ability tends to reduce impacts and lateral loads to such an extent that the edge retention increases. Up until the point you miss the wood and hit something else anyway.

Wow, I never thought about that! Another great point! Thank you for bringing it to my attention.

Dog of War--

Thanks for your info and confirming that I am on the right track. These were my first knife reprofiles so I wasn't 100% confident that I knew what I was doing. I must admit being a little nervous about removing a lot of metal from factory edges on fairly expensive knives, especially since I went from a thick convex edge to a much thinner V-edge.

I agree that it's very surprising what a difference thinning out the edge can make. When I first compared the reprofiled Battle Rat edge to a new factory BR (I like these knives so much I bought 2) it was hard to believe the new edge chopped so much better, even in very hard, dense, dry, dead wood.

I can understand inferior knives having thick edges to make up for their deficiencies but I don't know why high-quality knives also have them. I'm sure that manufacturers of high-quality knives know that thin edges cut better than thick ones. Even the smaller 4 1/2" knives I bought from Swamp Rat took some work to get the edge the way I think it should have come from the factory but, as with the BR, the results were worth it.

 

[Dog of War]

That was kind of gutsy, Mtn Hawk. I got introduced to more acute edges by my brother who designed industrial cutting tools and made knives as a hobby. But I remember at first wondering why manufacturers would put on such obtuse edges unless it was needed for something. I'm still not sure why so many of them do it other than it's less metal they have to remove, plus leaves an edge that will probably sustain less damage if somebody does something really extreme or careless with it. Be interesting to ask Jerry on the Busse forum.

I've never had the pleasure of taking two identical knives and comparing them like you have with your BR's, but I bet that was a real eye-opener. Something I've also noticed when reprofiling large blades like that is quite often you get less shock transmitted back into your hand and arm when chopping with the more acute profile. The difference in fatigue when doing a lot of work can be almost like night and day.

 

[Cliff Stamp]

I really thought I was making a mistake taking the Battle Rat down to about 12/15 but the only way I could find out if it worked was to try it. So far I'm very happy with the results on hard, dense, dry lower branches of fir and pine. Even on dead manzanita, the hardest wood I know of around here, it's holding up. I'm going to do a few more hours of chopping with it before I am confident I can leave it at those angles but so far so good.

That is actually a fairly standard wood working profile, or used to be anyway. There is some distortion of what is necessary for wood working tools, in particular note how people say "axe like" for edges which are too thick/obtuse to cut well, but actual edges on wood working axes have the same profile you describe. As a side effect of lowering edges for chopping you likely start to focus more on technique, probably a result of being hesitant of rippling the edge. This is one of the drawbacks to knives with overly robust edges, it tends to promote sloppy use.

I can understand inferior knives having thick edges to make up for their deficiencies but I don't know why high-quality knives also have them.

Generally they want a wider scope of work and want the knives to resist damage even in the hands of a aggressive novice. The Ratweiler I have was stock at 0.035" x 20 degrees, that is about perfect for that goal. For pure heavy wood work this could be cut down to 0.030" x 15 with a 20 degree micro, moving under this would risk failure on heavy batoning. Without batoning you can really slim out edges as it puts much more force across edges of lighter blades than chopping when you are working in problematic wood, which also brings up the point do you want to be able to cut that class of wood or not.

It is also a question (consider the manufacturer) of which problem do you want to deal with. If the edge is too thick/obtuse it takes maybe a minute on a belt sander to adjust, so a manufacturer can do it basically for a minimal fee and there is no damage done to the knife. If however the edge is so minimal that it ripples or fractures, then the blade is basically done and the user is out a tool, can't modify it, nor can the manufacturer as you can't add steel back to the edge. Now consider how each of those failures would likely influence the user once they were dealt with by the manufacturer.

As you get more skilled you will be able to work with slimmer profiles and move well out of the "average" user that production companies have to aim for. So you have to either start ordering custom edges, which Swamp Rat and Busse will do on request, or reprofiling yourself. The more work you do, the more extensive this will become. It was expect that when you bought a felling axe that you reworked the edge to suit your skill and local wood. You looked for the right primary grind, but the edges tended to need work, there is just too much variance from one person to the next (consider skill and strength) for the same profile to work well for everyone even on the same type of wood.

-Cliff

 

[Mtn Hawk]

The Ratweiler I have was stock at 0.035" x 20 degrees, that is about perfect for that goal. For pure heavy wood work this could be cut down to 0.030" x 15 with a 20 degree micro, moving under this would risk failure on heavy batoning. Without batoning you can really slim out edges as it puts much more force across edges of lighter blades than chopping when you are working in problematic wood, which also brings up the point do you want to be able to cut that class of wood or not.

I never considered there might be a difference in forces between batoning and chopping. I have not tested the 12/15 Battle Rat with batoning but will do this. Hopefully it will stand up to heavy batoning at this angle (as you said, steel can't be put back on). I think the Ratweiler blade is the same as the BR, only 2" shorter, but not sure. Almost all the firewood around here is very hard, dense fir and pine so I don't have much of a choice in what wood to cut.

Thank you for your explanation about sharpening angles and manufacturer's edges. That makes sense, since each knife owner is different and will have different uses for their knives and different performance expectations.

Dog of War--

After some months of reading posts and articles about reprofiling I finally got tired of just thinking about it and did it. My curiosity became greater than possibly screwing up a high-quality and fairly expensive knife. I was encouraged by a few posts from people who thinned out their blades but was surprised that most favor thicker edges. I'm happy it worked out and I learned a lot along the way. It's good to hear positive results about reprofiling and I appreciate your post.

Good points about why manufacturers leave thick edges on their knives. That makes sense.

Yes, I was quite surprised at the difference between the 2 BR edges. I kept chopping and comparing the 2 knives for quite some time, just to be sure of what I was seeing. I totally agree with you and Cliff about the decreased shock transmission with the more acute profile. With a 50% difference this would mean 400 chopping strokes instead of 600, a major savings of energy, especially in an emergency situation where energy conservation is critical.

 

[Cliff Stamp]

I never considered there might be a difference in forces between batoning and chopping.

It depends mainly on the size of your baton, you can use a baton many times heavier and longer than the knife which then induces far greater impact energies. Generally when you swing the knife you can get your power inline with the edge, this makes sure the knife experiences a compressive force which it can resist very strong, however if you baton, it is easier to cause the knife to twist, especially in trying to split a problematic piece of wood, and now the knife has to resist a bend across the edge and it is much weaker in that regard.

You can drastically reduce the force that the edge experiences by knowing where to place the knife to split the wood, mainly how to handle knots, to avoid having to cut them in half, split them directly if necessary and try to avoid either if possible. Then there is the ability to use wedges on the really bad wood, the larger chopping blades can cut wedges in literally seconds. On really seasoned wood which is full of cracks it can also often be pried apart and this is les stressful on the knife than having to chisel the edge through a bunch of knotty and twisted grain wood.

-Cliff

 

[DGG]

40 degrees total is the best angle. Profile at 30 degrees.

This edge should last a long time if the knife has good steel properly heat treated.

 

[gwb]

The Ratweiler I have was stock at 0.035" x 20 degrees...

-Cliff

What is the .035" measurement?

Is it the surface length (hypotenuse) from the knife edge to the intersection of the primary and secondary angle?

or

Is it the the horizontal distance (knife held vertical), from the intersections of the primary and secondary bevel on either side of the knife?

Thanks

 

[Cliff Stamp]

Is it the the horizontal distance (knife held vertical), from the intersections of the primary and secondary bevel on either side of the knife?

This, the thickness of the blade right behind the edge bevel, it ranges from about 0.005" to 0.050" for most knives.

-Cliff