Every stropped knife is Convex Edged and that is the best edge.

[USMCPOP]

I rock my big Thai knives/machetes back and forth on a rock like these. Start at a low angle to get the rust off, then gradually increase as I get tired of it. They end up convex and sharp. No problem with the crooked, pot-holed stones. They smooth out eventually.

 

[Obsessed with Edges]

Stropping doesn't remove nearly enough material to affect the shape of the entire cutting bevel.

Depends on what you're stropping with. I use denim over a hard backing (wood) with aluminum oxide stick compounds (usually grey or white rouge) to quickly convex & polish bevels in steels like 420HC or 440A. Could also work on more wear-resistant steels like 440C, VG-10, even D2, using black compound on the same material. The denim allows very dense loading of the compound, which makes the strop work very aggressively, both to convex and to polish very quickly. The key is laying the blade LOW, so only the shoulders of the V-bevels are being worked, so the sharp edge doesn't get rounded off.

Stropping on bare leather won't change anything very fast - that is true.

 

[OrangeBlueOrangeBlue]

All depends on pressure and compound , so you can strop possibly without removing significant material. The other material on that leading edge, unless the stropping surface has no give and is flat, Would comvex

Depends on what you're stropping with. I use denim over a hard backing (wood) with aluminum oxide stick compounds (usually grey or white rouge) to quickly convex & polish bevels in steels like 420HC or 440A. Could also work on more wear-resistant steels like 440C, VG-10, even D2, using black compound on the same material. The denim allows very dense loading of the compound, which makes the strop work very aggressively, both to convex and to polish very quickly. The key is laying the blade LOW, so only the shoulders of the V-bevels are being worked, so the sharp edge doesn't get rounded off.

Grey Rouge is around 1200 grit and White Rouge is in the 1-3 micron range, so 1500 grit at the coarse end. Basic geometry dictates that you can either keep the same ultimate edge location and knock down the shoulders where the cutting bevel meets the main bevel or keep the same shoulders (the points where the main bevel transitions into the cutting bevel) and create a convex bevel within the outline of the existing cutting bevel (this is the one that creates a substantial difference in thickness behind the edge). Either way, you have to remove a LOT of material to turn a straight bevel into a convex one, because you're essentially reprofiling. Even with aggressive abrasives, that's a lot of material to remove; at 1200+ grit, it'll take a long time. If that's the goal, you're probably better off just using wet/dry sandpaper instead of a strop.

 

[Obsessed with Edges]

Grey Rouge is around 1200 grit and White Rouge is in the 1-3 micron range, so 1500 grit at the coarse end. Basic geometry dictates that you can either keep the same ultimate edge location and knock down the shoulders where the cutting bevel meets the main bevel or keep the same shoulders (the points where the main bevel transitions into the cutting bevel) and create a convex bevel within the outline of the existing cutting bevel (this is the one that creates a substantial difference in thickness behind the edge). Either way, you have to remove a LOT of material to turn a straight bevel into a convex one, because you're essentially reprofiling. Even with aggressive abrasives, that's a lot of material to remove; at 1200+ grit, it'll take a long time. If that's the goal, you're probably better off just using wet/dry sandpaper instead of a strop.

With the grey or white stick compound heavily loaded on a hard-backed denim strop of 12" - 15" length, it takes maybe 10 minutes or less to convex & polish the bevels on a folder-sized blade in 420HC or 440A. Blades like traditional folders from Case or Buck up to folding hunter size, for example. Even fine-grade aluminum oxide is very aggressive on steels like these. I know this, because I've done it this way many times. It works very fast. It's not just about the grit size, but in the density to which the compound is loaded on the denim strop. And the very hard, firm backing to the denim makes it work even faster.

 

[HeavyHanded]

If you bear down on any conformable surface loaded with compound you'll get a convex at the cutting edge even with submicron abrasive.

In practice it is only as "good" as the final edge angle - an overstropped convex edge is a poor cutter compared to one that terminates with only a degree or two of widening. I prefer to do my convex edges on a hard stone most of the time for this very reason.

A flat cutting edge with a microbevel is going to cut every bit as well with one exception - big choppers go through material with less drag when the whole bladed is convexed due to the very gradual nature of the wedging action on a convex surface. Aside from that any thin ground and well sharpened edge is going to cut well.

 

[OrangeBlueOrangeBlue]

In practice it is only as "good" as the final edge angle - an overstropped convex edge is a poor cutter compared to one that terminates with only a degree or two of widening. I prefer to do my convex edges on a hard stone most of the time for this very reason.

If you convex an existing triangular cutting bevel (not touching the main bevel of the knife), it will always end up with a more obtuse edge angle than it had before.

 

[HeavyHanded]

If you convex an existing triangular cutting bevel (not touching the main bevel of the knife), it will always end up with a more obtuse edge angle than it had before.

Yes. This is true if you apply a microbevel as well. It is possible to do both with only a couple of degrees total or per side, and that generally provides the best outcome.

Sort of a wildcard is when you microbevel a very coarse edge using a much finer stone or very hard strop surface - The resulting edge is less acute, but because it reduced the side to side variance across the apex, the cutting edge effectively becomes thinner.

 

[kobold]

I usually start by knocking off the shoulders of an FFG bevel aiming for a convex surface. No abrasives ever touch the apex, it maintains the factory acuteness. But the TBE is now both thinner and curved. For me this is a win-win-win. I leave it to usual wear-tear and usual freehand sharpening to advance the geometry towards a more blended shape. It is a problem that solves itself.

 

[FortyTwoBlades]

The reason why stropped edges become stronger is that you've increased your edge angle. They have more material behind the edge because the angle is thicker, not because they're stronger at equal edge angle. In fact, the opposite is true. When edge angle is held constant the convex is like a V-edge with the shoulder rounded off, and so has less of a "speed bump" with an edge that's almost as strong--that is to say that the gains in cutting performance are greater than the loss in durability from the removal of that material.

 

[Obsessed with Edges]

Throwing these pics in for fun. Agree with earlier comments about convexing the shoulders of V-bevels and leaving the V-edge alone, save perhaps for some delicate polishing done carefully to protect the apex angle. The biggest benefit is reducing the drag created by hard-edged bevel shoulders. Less about the strength of the edge itself, which changes negligibly in my experience - that's more about the steel, it's hardness and the edge angle itself, whether it's 'V' or convexed. And polishing the radiused shoulders, after convexing, reduces drag even further.

And it just looks so darned good.

 

[stitchawl]

I rock my big Thai knives/machetes back and forth on a rock like these. Start at a low angle to get the rust off, then gradually increase as I get tired of it. They end up convex and sharp. No problem with the crooked, pot-holed stones. They smooth out eventually.

View attachment 1645872View attachment 1645874

Looks like typical Thailand workingman's gear! Nice thing about them is that it's all so inexpensive, both stones and knives. Knife wears out? Just stop at one of the bamboo stalls along the side of the road and have your pick from dozens of different sizes and shapes, all for the price of a McD's Happy Meal!


Stitchawl

 

[USMCPOP]

Looks like typical Thailand workingman's gear! Nice thing about them is that it's all so inexpensive, both stones and knives. Knife wears out? Just stop at one of the bamboo stalls along the side of the road and have your pick from dozens of different sizes and shapes, all for the price of a McD's Happy Meal!


Stitchawl

The knife on the far left with the metal-banded sheath cost me about $5, 44 years ago. But it's a beautifully made Mien/Yao hilltribe knife. The one in the middle with the octagonal handle and deluxe blue plastic drainpipe sheath was about $2 many years later.

I think a cheeseburger meal (~ $4.) is just a bit more than an average farmer knife.

Blacksmiths there will recondition a knife for half the price of a new knife, or less.



I'd like to visit Laos or Myanmar and get some knives.

 

[Lesknife]

I would think that putting a convex on a flat ground bevel would be very minimal and mostly at the apex and the transition points and not really a significant difference from a micro bevel. If you are cutting stuff that includes abrasives then it has similar a effect anyway but the apex gets dull.

In my experience trying to maintain a proper convex edge involves more time than I’m willing to invest. I have found that in my general usage a flat 15 dps bevel is sufficient and if I encounter some tough materials I can always put a micro bevel on it for good results. I do strop some between sharpening or touch up the edge with a fine diamond sharpener but I don’t worry about getting a real convex edge when a flat bevel does the job to my satisfaction. It’s not like I’m chopping bamboo every day.

 

[FortyTwoBlades]

Functionally speaking you don't have to worry about maintaining a perfect convex on knives with a convex primary grind. You'll just need to eventually thin the cheeks back out to preserve equally thin cutting geometry as it originally had. But that's technically true of all knives as you wear back into a conventional flat grind. One of the major appeals of hollow grinds is that it reduces the need for work of that kind.

 

[Obsessed with Edges]

Functionally speaking you don't have to worry about maintaining a perfect convex on knives with a convex primary grind. You'll just need to eventually thin the cheeks back out to preserve equally thin cutting geometry as it originally had. But that's technically true of all knives as you wear back into a conventional flat grind. One of the major appeals of hollow grinds is that it reduces the need for work of that kind.

My habitual tendency is to lay the blade just a hair lower in angle, each time I resharpen. This means most of the 'sharpening' is actually just thinning the grind a little more behind the edge, for the most part, with a minimum amount of work actually needed at the edge itself. And as the steel behind the edge gets thinner over time, it becomes that much less work to tune up the edge itself. So, one feeds the other, and it just keeps getting easier with time.

 

[EdgePal]

To keep a flat edge flat by freehand sharpening when you sit down comfortble at home can be done, mostly becouse you cannot meassure whar you have done to the blade. One sharpening take away e very small amount material from the blade. 100 sharpenings together = you can clearly se what you have done ro the blade - and now it is coearly convex.

A industrial robot have not more then 3 joints. Every joint have a small "give" to be able to move. Three joints give together givs a lack in precission. Precission made robots have lesser lack - but they are very expensive to by.

In freehand sharpening we use 34 joints = a very big give. To the 34 joints we also use muscles and so on. This together makes that we humans can not come below 3 degrees wobble when we freehand sharpen. Combine this knowledge with what I wrote above, we cannot meassure this in one normal sharpening, but the dripp destroys the stone over time = we can se it after many sharpenings, and also meassure it.

I lived outdoors 6 month every year, far away from civilization. When I started live like that my two knifes had flat edges. After 6 month daily sharpening, the edges was convex. I saw this the first year and analyzed it and understood what has happend. Then Intryed hard to hold the edges flat next 6 month, but hey become convex - but lesser convex then the first 6 month, after 20 years outddor living, 6 month every year, i was down to 3 degrees wobble the last 10 years.

I have made resurch and testings about this also, and they all tells that we humans can not come below 3 degrees wobble when we freehand sharpen edges.

One very good help to se, and understand, this are ro make a very simple tool that shows what I talk about = how the wobble looks like - and how the wobble can be meassured.

I fasten a lazerpointer on a piece of metal angled in 10 degrees. On the downside I have mounted a strong magnet that I place on the upper side of the blade. When I now move the blade, the red dot also move.

I place a sharpener on a table with its middle 54 cm from a "target". In this distance 1 cm = 1 degree. I make a line on the target that shows the 10 degree angle, and then I make three lines above, and below this 10 degree line. When I sharpen as I normally do, the red dot shall not leave the 10 degree lina on the taget verticly but it can move horistontal along this line.

If you can keep the red dot exactly along the 10 degree line you will make a 100 % flat edge - but as you will se, it is inpossible to do by hand. The red dot will move at least 3 degrees, probebly much more then that verticly..

I recomend you to make this tool. The cost are small, you can use a cat toy lazer for 5 USD, it works fine.

Take a video when you do this and concentrate abouy to hold the 10 degree line and look at the video after this test of your skill. You must be fully concentrated on the sharpening. Be preaperd for a chock...

I have test this on hunderds of people that I know can sharpen during the years. i know what you will se when you do this...

If you clime that you can hold the 10 degree line all the time during 30 seconds sharpening you must show a video when you so it. Tye video shall show the sharpwner, your hands, the knife - and the target all the time during this 30 seconds sharpening. I have, during 20 years, never seen it be done. Everyone that have tryed this wobble more then 3 degrees.

This tool are also a good tool to use to ahow HOW you are wobble. Is it mosrly above, or below, the 10 degree line? Is it more close to the handle,mor the tip?
You can alsoo se that when you use this tool, that you will wobble less during time. First when you know what you are doing - you can make improvments and meassure them.

<a href="https://ibb.co/NpTvtSh"><img src="https://i.ibb.co/5vK0GFD/MINOLTA-DIGITAL-CAMERA.jpg" alt="MINOLTA-DIGITAL-CAMERA" border="0" /></a>

 

[EdgePal]

Convex edges has been discussed during a very long time. They are not superial in any way, they are just a type of edge I choose on my knifes becouse I need a convex edge to do what I do.

In the same way I use flat edge when I need a flat edge - or other types of edges whan I need that.

Flat edges are perfect for whittling - and convex edges are very bad for whittling. Convex edges works perfect outdoors and are easy to maintain becouse you can take benefit of yoir wobble when you sharpen them.

There is not any superial edges - but there are many different edges that you can use to just that you need to do shall be simpler to do.

A lorry can transport more sand then a ww-bug. But both are cars...

 

[murat1983]

There us no doubt that convex knives are strongest behind the edge, simple due to more material and edge support. This is simply physics. That said, I learned this by owning a Bark River which come this way which I now love. What many do not realize is that if you stop a blade on leather, you always create a convex edge, so all my folders become convex at least on the edge and are usually mirror finished by the time I am done. Most manufactures do not create convex edges as it requires more skill and time and most sharpeners do not create this type of edge as their sharpening surface us hard or designed to grind material sharp fast. I think if we, the market, asked and looked for this, the makers and manufactirers would follow, Knife sharpening conpanies would create more tools oriented to this tipe of blade or final edge and the world would be a better place. Blades would stay sharper longer.

This is correct to a certain extend, but in some cases, convexing is so minor that it can be ignored. For instance, if I want a noticeable convexed bevel, I use a regular 2-3mm thick leather strop. If I want micro convex in flat bevel then I use my 0.6-0.8mm kangaroo leather strop. I am stropping a scandi grind knife or if I try to avoid or minimise the convex on the bevel then I use my basswood strops.

 

[EdgePal]

Bark River knifes convex edges hold 2-3 convex sphere per side.
Fallkniven convex edges hold 6 degrees convex sphere per side and have 20 dps close to the handle and 13.5 dps close to the tip. Not easy to maintain that edge by freehand without changing the edge.

Sligthly convex = 1-2 degrees.
Medium convex = 2 -4 degrees and
heavy convex 4 -7 degrees

Convex edges are not just "convex". A slightly convex edge work very different then a heavy convex edge do.

I invented the bended/angled guide rod that grind convex edges perfect for soon 20 years ago and it took long time to find it out - and a lot of testings. A bended or angled guide rod gives convex spheres in wanted degrees and also wanted degrees on the cutting edge. This make it easy to maintain the convex edge without any changes of the convex sphere or the degrees on the cutting edge.
The convex guide rod also make it possible to tell another person how to use the guide rod and I can use numbers that he can use ta for example exactly grind the same convex edge I have on my knife. We can comunicate our convex edges in the same way people for hundereds of years have been able to comunicate flat edges in degrees. Convex edges needs more numbers then degrees and they need the same sort of guide rod to do it, but it is as simple as with flat edges really.

The problem is that 99,99 % of all people that have a knife with cinvex edge have not a cloue about the knifes convex sphere or what degrees there is on the cutting edge - but they know that the edge is convex... Tha fact that convex edges earlyer cant be communicated was that convex edges are more difficult to sharpen becouse they have a convex sphere that must be maintained and a cutting edge. If I do not can meassure those things I will change them both slightly every time I sharpen my knife - and that will worn out the cutting edge, or the convex aphere will change heavy, over time. For a person that use his knife much, that is a big problem. For normal knifeusers it smaller praoblem - and most users do not even notice it. So, it depends on how much I work with my knifes and how often I must sharpen them. Freehand change the edge, a convex guide maintain the convex edge withoiut changing it - and that alao means that the blade get a long life becouse eveey maintainens sharowning take away very little material from the blade.

Those problems was the reason that I decided to solve the peoblems tecnical - and the bended/angled guide rod was my solution for 20 years ago - and it is still, after 20 years, the only solution to those problems.

So, convex edges are made very different, they have all different convex spheres and different degrees on their cutting edge = more, or less, material in, and behind, the edge. That is why no edge type are superial or best. To say that - the convex edge first must be defined in degrees on the cutting edge and in degrees on the convex sphere.

 

[FortyTwoBlades]

Curved guide rods still don't necessarily give you repeatable results from session to session or knife to knife. You'd have to do a lot of careful calibration in order to end up with the same results session to session.