Cold Steel machete + Worksharp sander = convex edge (56K!)

[Sworbeyegib]

It's no secret, I have a slight addiction to machetes and big choppers. And I am a huge fan of Cold Steel's machetes, and own more than I care to admit.

I find the steel (1055) to be a very good machete steel. The thickness is slightly beefier than a typical hardware store machete, but they aren't "thick" choppers, like a kukri, or one of Storm Crow's bush swords. They still retain enough flexibility and whippy-ness that classify them as machetes. I also enjoy their variety of blade shapes and designs, patterned after both traditional work knives and swords.

However, there is a big glaring issue that I have with Cold Steel machetes. The factory edges SUCK. And since Cold Steel markets themselves as the world's "strongest, sharpest knives.", it is a bit of a let down. But I get it. It's how they save money, to put out a good product for a cheap price tag.

This is how their machete's used to be sold from the factory. This is one of their older Barong machetes that I bought a few of, and I never got around to touching this one yet.



Note that the black coating they use goes all the way down to the edge. They used to call this a "utility" edge. I call it dull and unusable. The grind is right, but it is essentially and unfinished blade IMO.

Even though it looks very flat ground and slightly "scandi-ish", after taking a file to remove the coating, it is very apparent right away there is a slight concave, or "hollow ground" section to the edge. The very tip of the edge, and the shoulder of the angle would wear off first, and the middle section would remain untouched until a larger amount of material is removed. This concave is either from how it is pressed, or from the wheel they used to grind the angle out. I'm not exactly sure how they make them.

The last few machetes I've bought from them in the last year or so do not have the problem with the coating anymore. However, I do not know if this is because of the specific models and factory where my machete's were made, of if it is company wide.

Here is a pic of the latest machete I bought.



Note that the edge is now uncoated, and is roughly sharpened. After taking a file to it for a few seconds, this to also has a concave to it, and is not truly flat.

The edge itself is an improvement over the previous, but is still rough, and has a slight wire edge to it. I would say this is acceptable enough for some tasks, and a few minutes with a file or hard grit stone would get it good enough for a "utility" edge.

However, I put my blades to rough use. Not just clearing light stuff, but for chopping heavy stuff too. Edge retention and toughness is a big thing for me, as I've seen cheap machete's roll edges and crap out on me when I'm beating on them.

Once I learned about convex edges, I was intrigued. Once I properly reprofiled and used a convex edge machete, I was hooked.

For those of you not familiar, he is a little graphic.



For the sake of this thread, and for the machete's I have done, when I am referring to a convex edge, I am talking about a single bevel convex blade. So similar to a scandi grind, in terms that there is no primary grind with a secondary bevel for the edge. Just one consistent grind that runs from shoulder to edge.

The curvature of a convex edge allows for a very tough, yet relatively thin edge. Even though you are shaving off some of the beefiness on the shoulder, the seemless transition from the relief edge to shoulder allows for more support where it matter most. It also helps reducing wedging of the blade in thick materiel, and reduces edge contact. Especially when batoning.

It may not have to same kind of godly bushcraft carving control as a scandi grind. And it may not seem as "hair splitting" as hollow or some flat ground edges... But with a good angle and with a good honing, it still passes all the usual tests. Shaving, fingernail, paper slice etc... It's a very tiny trade off, for a huge gain in edge retention. When it comes to choppers, I would much rather have a blade that stays as sharp as an 8/10 for an entire day, than a blade that can get to 10/10 sharpness, that dulls to a 5/10 in an hour of hard use.

It's really hard to capture just how pretty a nice convex edge is on camera, due to the curvature of the blade catching the light, so the pic really doesn't do it justice.





Many people like to use the sandpaper + mousepad trick to create a convex edge. But since these are big knives, with deep grinds, that I'm reprofiling... I aint got time for that. Most shops use a stationary slack belt sander to create a deep convex like what I try to obtain. But I live in an apartment, and heavy machinery is generally frowned upon.

Luckily, santa brought me a nifty present a few years ago that I've put to a lot of good use. The Worksharp Knife and Tool Sharpener.



It comes with 3 grits of sand paper. 220 for general purpose sharpening, 6000 grit from honing, and 80 grit for heavy material removal. The belt has a nice amount of slack to it, due to the spring on one of the guide ends.



It comes with 2 different guides. One for outdoors blades, and one for kitchen blades. However, I really don't like using the guides very much. Especially for larger blades. That's why I'm glad you can remove the guide, and rotate the head.



Now I can use it more like a hand sander, or an angle grinder. This makes it great to use on things like shovels, and axes. But more importantly, it gives me much more control in the angle and material I remove when reprofiling an edge.



As you can see from the picture, the belt conforms around the edge.

I don't have any pics or video of me actually using it, but that's because I do not have a camera man to snap a few off. So luckily for you guys, this is where the pictures come to an end.

Since I had to remove a good chunk of steel from both the edge and the shoulder to turn the factory grind into a convex, that means that one of the important things I must do is widen the relief edge up as much as possible, by backing where I want the shoulder to be as much as possible. If I don't, then by the time I've shaved enough material away for the convex, the geometry of the edge would be a bit too "short and fat" for my liking.

This is a bit tricky with the slack sander, but easily doable. I apply as little pressure as possible, so that minimal curving of the belt occurs. In the past I used to use a file or dremel tool, but I've gotten good enough with the Worksharp to not need it.

Once I back the grind up far enough to where I want it to begin, it's a piece of cake. I'll use the 80 grit to keep grinding away at the edge, until I can see the middle of the grid is being affected. Usually for the first few minutes, only the shoulder and edge are in actual contact with the sanding belt. I'll use a black marker to mark the edge between runs, to check for any spots that are not in contact with the belt.

I'd say that an average 18" machete takes between 15-20 minutes on the 80 grit before it finally is reprofiled to my liking. After that, it is a breeze. I do less than 5 minutes on the 220 grit, mostly to even out the trouble spots, and to remove the wire edge. And finally, a quicky buff with the 6000 grit.

This has been standard operating procedure for all of my big choppers, and a few of my fixed blades. Luckily, Cold Steel's machete's come with a primary grind suitable enough to make reprofiling it fairly simple. Not all blades are like this. If a blade's stock is just too thin, or the hollow grind on it is just too deep, it really isn't suited for full convex edge. In fact, I'd say any thinner than what they use and I probably wouldn't do it.

The edge retention is fantastic. I'm sure part of that is due to the decent 1055 carbon steel they use, but the new edge optimizes it. I can't remember the last time I actually needed to resharpen one of them during the day. I just touch them up once in awhile when I'm bored.

Do I wish Cold Steel sold their machetes with a convex edge from the factory? That'd be nice, but then they wouldn't be selling them for $20 or less anymore. And that's kind of the beauty of these big knives. Condor does convex edges on their big choppers nowadays, but their prices have also significantly risen since doing so.

Thanks for putting up with my long post, with incredibly unexciting pictures. I'm just an amateur knife lover that likes to dabble in making things fit my needs, so any input or advice from people out there is greatly appreciated.

[JackBauer]

Awesome post! Thanks for sharing you technique. Very informative.

I have several of the cold steel kukri's and machetes that will get the "Sworbeyegib" treatment

[raptor]

Awesome post! Thanks for sharing it!

[mr_slappy75]

This is bar none the best plain English breakdown of what a convex edge is, what it brings to the table and how to get it there; Some of this stuff I knew -most I really didn't- but I could not explain it better than you have.

I am copying this and saving it to view offline. Thanks man!

[Sworbeyegib]

A lot of credit has to go to the Worksharp, it's one of the best pieces of equipment I own. It really deserves a thread of it's own.
One of the things I also like to use it for, is smoothing and shaping the contours of wood handles of knives and other tools. The thin belt really makes it easy for detail work, and the slack helps keep the contours smooth.

There are definite drawbacks and such to the Worksharp, that I've worked out thru trial and error over the years. It really isn't suitable for establishing a primary grind, but can be used to slightly modify one if the angles are right. The Cold Steel machetes utilize a single bevel saber grind (scandi) grind, that makes them perfect to convert to a convex. However, most knives typically bought and used in the US incorporate a double bevel. Which means the primary grind and the edge are two separate angles.

There are 3 types of convex grinds as I perceive it, though I'm know authority on the subject.

-Full convex grinds start tapering down from the spine, like a full flat grind does. Or at the very least, very close to where the spine is. I believe Bark River uses this on their knives. This is a very good grind, but the thickness and width of the blade needs to be in proper proportion to the grind and purpose of the blade for it to be effective. If a blade stock is too thin, and the blades profile is too wide, then you really don't have much in the way of tapering. If the blade is too thick, and the profile too narrow, then the edge will resemble more of an axe than a knife.

-Saber or scandi convex grinds are what I utilized. This means that the sides of the blade are flat and parallel up until where the grind starts (generally less than an inch from the edge). The convexing then is a single bevel until the edge of the blade. I find this is great for thin choppers.

-Lastly, is just a secondary convex edge. Most knives bought and used in the US have 2 bevels. A primary grind (which could be saber, flat, hollow etc...), and a secondary bevel that changes angles and meet to become your edge. That secondary angle and bevel is what you are actually sharpening and touching to stone. Typically it meets at a V grind from sharpening on a flat surface. But you are also able to sharpen just the secondary bevel of most knives to a convex edge if you wish.

However, different blades will take better to a convexed secondary edge better than others. I find that full flat ground knives generally benefit from one. Hollow ground knives... it really depends on the blade. How shallow or how deep it is ground out, and how high back the primary grind is to the spine.

Convex edges aren't really meant for every person or every knife. I don't find that they don't carve as well, for fine things and detail work. It'll still work, but I find it doesn't bite into the wood as naturally. The curvature of the shoulder that reduces the surface contact area and wedging, actually gives you less control of the blade. I think the reason for this, is because the convex makes the edge want to "scoop" out of the wood you are carving into.

[ineffableone]

The Worksharp is a great tool for sharpening. Even though I still enjoy stone sharpening, I use my Worksharp when I don't have the time or have a lot of blades to sharpen at once. And of course the Worksharp is not a field sharpener, trees don't have an electrical outlet. So don't let your other sharpening skills atrophy if you do get a Worrksharp. BTW there is also the Ken Onion version, which is more expensive but has features like variable speeds, and different attachments options etc. Which to get is mostly a matter of how you plan to use it. If your just doing a bit of sharpening then the original but if you plan to use it as a general grinder for different tasks the Ken Onion might be the better option.

Convex edges aren't really meant for every person or every knife. I don't find that they don't carve as well, for fine things and detail work. It'll still work, but I find it doesn't bite into the wood as naturally. The curvature of the shoulder that reduces the surface contact area and wedging, actually gives you less control of the blade. I think the reason for this, is because the convex makes the edge want to "scoop" out of the wood you are carving into.

This is very true. While I prefer convex grinds on my blade I do have to recognize they do have their time and place. Fine carving and convex bevel grinds don't go together very well (see full convex bellow for exception). Which is likely why bushcrafters tend to prefer scandi grind on their knifes so much. With convex you can only get so far in carving before the grind starts to work against you. But with a scandi grind you can get much more detailed and finer cuts. However for deep cutting convex actually can be a better grind. As seen in this video.



More and more bushcrafters are starting to see the benefits of convex grind blades. Many bushcraft knife makers are now starting to offer convex options. Though the option is only hybrids or convex bevels rather than full convex. Bark River does not offer a full convex sadly, their convex does not go all the way to the spine but up to a flat. How far to the flat depends on the style of knife.

Something to note there is a big difference between a modified convex where the bevel has been knocked down and covexed and a blade that was designed full convex. As seen in this picture.



The full convex will actually perform better in fine carving than a modified convex/convex bevel. Which is likely why a lot of people feel convex is poor at fine carving, a full convex grind can actually do some superior carving to a scandi grind due to having no bevel to push away from the wood. Of course the problem is there is no production knife makers I know of that make full convex bushcraft type knives. The only way to get a full convex blade is to find a custom knife maker who actually knows how to make one properly. Which is not very many custom knife makers. And it will cost a lot of money (in comparison to scandi or convex bevel) as a full convex is a lot of work to get a full even convex on a blade.

[Sworbeyegib]

I've been eye balling that Ken Onion Edition for awhile now. My local gun store has one, and I see it every time I go to buy new belts for my basic one. One day I might get it, but at almost double the cost of the original, I can't really justify it quite yet. Especially since I'd need to pay another $70 on top of that, to get the aftermarket attachment that really makes it more versatile.

True convex edges from spine to edge are definitely very rare, outside of the custom knife world. Not only is it much more painstaking to do, but there are so many inconsistencies that can happen when working with a curvature rather than flat edges and angles that can happen. How deep or shallow you wish to have your "cheeks" or steepness on a convex edge is personal preference, depending on how you will be using the blade.

For me, I'm just an amateur bushcrafter. I actually don't do too much when in camp to need absolute precision and performance for fine tasks. About 90% of my edge duties is simply wood processing, at which point the hybrid convex on a machete comes in handy, since i do not bring an axe out with me. I often chop and process wood that some people would say is to hard/thick to use a machete on.

I utilize what I call a M&M&M combo most of the time when I'm out in the bush. Machete + Mora + Multitool. Covers just about every base I need to. Occasionally I'll have a mid sized fixed blade in the mix, but it really depends on what I'm doing out there.

[Paladin1]

Nice write up!

[Valarius]

Just wanted to comment on this thread. Thanks for posting it and reminding me about convex grinds. I'll be trying one when I finish my next knife.

[Sworbeyegib]

I've been thinking of buying a few extra mora knives of various thicknesses to play around with in converting to a convex edge. Probably more than a few people have done this on other forums, but I just want to play around to see if anything works for me.

For my uses, I'm generally not interested in investing in a proper, full convex edge on a "bushcraft" style knife. My primary use of a convex edge is simply for added edge retention in heavy choppers. But I figure I'll give it a whirl.

[mr_slappy75]

I've been eye balling that Ken Onion Edition for awhile now. My local gun store has one, and I see it every time I go to buy new belts for my basic one. One day I might get it, but at almost double the cost of the original, I can't really justify it quite yet. Especially since I'd need to pay another $70 on top of that, to get the aftermarket attachment that really makes it more versatile.

I became aware of the WorkSharp about 2-3 years back at first I saw a lot of mixed reviews, so even when occasionally I would come across pretty good deals locally or online, I hesitated to pull the trigger.

Checking up on it more recently in places like bladeforums and bushcraft USA (and your write up of course) the consensus seems to have become a lot more favorable.

Do you think it is because folks have gotten better and more informed about proper usage and hacks? I see them on Ebay, often times NIB starting at $60 - $80, about a month ago I saw a Ken Onion one go for under $100.

Damn now I want one !

[Sworbeyegib]

I've been eye balling that Ken Onion Edition for awhile now. My local gun store has one, and I see it every time I go to buy new belts for my basic one. One day I might get it, but at almost double the cost of the original, I can't really justify it quite yet. Especially since I'd need to pay another $70 on top of that, to get the aftermarket attachment that really makes it more versatile.

I became aware of the WorkSharp about 2-3 years back at first I saw a lot of mixed reviews, so even when occasionally I would come across pretty good deals locally or online, I hesitated to pull the trigger.

Checking up on it more recently in places like bladeforums and bushcraft USA (and your write up of course) the consensus seems to have become a lot more favorable.

Do you think it is because folks have gotten better and more informed about proper usage and hacks? I see them on Ebay, often times NIB starting at $60 - $80, about a month ago I saw a Ken Onion one go for under $100.

Damn now I want one !

One thing I learned about using the sharpener.

If you are using it "as per instructions", you need to be very careful about using the angled guides. If you are the kind of person the does not like to ruin the coating and finish of their blade, you definately need to tape the sides of your blade if you are going to use it.

When using the angled guides, you rest one side of your knife flat against the guide, and slowly draw back. However, since there is so much fine metal dust everywhere when using this machine, it will quickly rub and scratch off the finish of your blade. I can just imagine someone wanting to touch up some $400 collectors blade, only to rub scratch and scuff marks into the side of the blade.

I'll try and find a knife of mine that it happened to and post a pic.