Thin Edge Preservation

[Sharp24/7]

Sorry if the title isn’t clear, I was trying to avoid typing a mouthful. Im curious if anyone has advice on how to keep your knives thin behind the edge. Like a lot of forumites, I enjoy experimenting with different edge finishes, etc. The bulk of the metal comes from reprofiling down to about 16dps on the Edge Pro. For those that don’t know the EP lets you sharpen on the face of the blade or on the flat. But that’s a little hard to translate to an ffg folder, so I rest the face of the blade on the table, below the plunge line. Point is, the angle is a best guess. Once I have the angle set, the experimenting begins. I’m guessing I’m not sharpening away that much metal, so maybe I don’t have to worry to much about thickening behind the edge. But regardless I’d like to know how everyone keeps that sweet, sweet, BTE thinness.

[p_atrick]

Not sure if I am addressing the issue you brought up, but Murray Carter advocates thinning your knife at every sharpening. You are not taking much off. The idea is that, over time, your stock is getting thinner as you grind away more metal at the apex. The overall geometry should not be that much worse as your knife ages.

Not sure if a fixed angle system is good for this, but a double-sided King Deluxe 1k/6k should work. I do this mostly with my kitchen knife. It is only okay as far as knives go. If I mess it up, then I have excuse to get a better one. The finish on the knife won't look as good as from the factory though.

[Strauss95]

Attempting to thin many of these super steels we have nowadays can be quite the chore. I've a big fan on having a high performance knife, so most factory grinds are too thick behind the edge IMO, let alone after multiple sharpening sessions.

I know there are few people out there that do quality regrinds, but it can be tough to find those people and their services. I have been interested in sending a few of my own out to someone but I'm not sure who to send them too.

Thinning a much softer steel kitchen knife that is already thinner behind the edge than our pocket knives is a much easier task, and even that is usually fairly time consuming. A custom regrind is the best way to go about thinning behind the edge on our pocket knives.

The Edge Pro is not ideal for thinning. That is best done freehand on bench stones since you need a very shallow angle, lower than the EP will go. Using a belt sander will be the fastest, but I feel that is best left to the pros since you can screw a knife up really quickly.

[Bolster]

Patrick: Are you (or Carter) talking about laying a FFG blade flat on a bench stone and reducing the overall thickness of the blade? That's the only preferred way I know to keep the BTE thickness down, as a knife goes through multiple sharpenings. Of course it destroys markings on the blade.

Sharp: I really did not get along with an Edge Pro and finally sold it, due to the lack of a solid clamp system. I replaced it with a Hapstone which I get along much better with. But neither sharpening system would keep the BTE thickness down; for that, reducing the width of the entire blade would be the way to go. Short of that, you could grind a steep back-bevel that would get you partway there. But a lot of guided systems don't go much below 12 degrees, IIRC.

[Josh Crutchley]

This is the only knife I've thinned out. I used Harbour Freight diamond plates freehand.

Not the prettiest but it cuts like a dream.

[Wandering_About]

I tend to lay back most of the main bevel to a pretty thin angle (maybe 10-13 degrees per side, and a bit convexed because it's done freehand) then put a "microbevel" on that suits the steel type and my intended use case for each knife. It's a compromise between a few things, including not doing a full regrind, keeping some durability at the edge, and still improving cutting performance. The behind the edge measurement at the top of my bevels on these kind of reprofiles is kind of huge, but it starts to lose meaning a bit because the bevel is laid back so far.

[Sharp24/7]

I tend to lay back most of the main bevel to a pretty thin angle (maybe 10-13 degrees per side, and a bit convexed because it's done freehand) then put a "microbevel" on that suits the steel type and my intended use case for each knife. It's a compromise between a few things, including not doing a full regrind, keeping some durability at the edge, and still improving cutting performance. The behind the edge measurement at the top of my bevels on these kind of reprofiles is kind of huge, but it starts to lose meaning a bit because the bevel is laid back so far.

Mine came with bevels laid back pretty far, but much more so on one side.

[RustyIron]

I’m guessing I’m not sharpening away that much metal, so maybe I don’t have to worry to much about thickening behind the edge.

Yeah, you're overthinking this a little. Of course you thicken the area behind the edge when you sharpen to a more acute angle, but the amount is small. Even on my most used and resharpened Spyderco, the amount is not substantial.

For those that don’t know the EP lets you sharpen on the face of the blade or on the flat. But that’s a little hard to translate to an ffg folder, so I rest the face of the blade on the table, below the plunge line. Point is, the angle is a best guess.

I understand what you're saying. It's not difficult to figure out the angle of the edge you can recall your high school geometry and trigonometry.

As you've noticed, you can set up your EdgePro to 15 degrees. But the sides of the blade are not parallel, so the blade is tipped downward on the table, making the angle more acute. All you need to do is subtract half the angle of the blade, and that will be half the angle of your edge. In other words, your sharpener is set to 15 degrees, half the angle of the Spyderco blade is 2 degrees, so your edge will actually be 13 degrees.

To determine the angle of the FFG, measure the thickness of the spine. Mark a point 1.000" down from the spine, and measure that. Now you have three dimensions of a trapezoid. Chop it up on your notepad until you have a triangle. Now solve for the unknown angles. Easy peasy.

I just did that on two Manixes. My measurements are crude: the 1" mark was measured with a ruler on and marked with a Sharpie. Nevertheless, one Manix is about 2.2 degrees per side, the other is 2.1 degrees. I also measured a Native 5, and the numbers looked consistent with the others, although I didn't do the math.

It's safe to say that using 4 degrees will get you in the ballpark. There are other variables, so trying to figure it out more precisely is a bit pointless. Sharpen to get a nice edge, not to meet an arbitrary number.

[Bill1170]

Murray Carter’s recommendation is squarely in line with standard practice on chef’s knives. As the steel is worn away the knife shrinks but proper geometry is preserved.

[p_atrick]

Patrick: Are you (or Carter) talking about laying a FFG blade flat on a bench stone and reducing the overall thickness of the blade? That's the only preferred way I know to keep the BTE thickness down, as a knife goes through multiple sharpenings. Of course it destroys markings on the blade.

Yup, lay it down and start thinning. I've done it to two Spydercos in addition to my kitchen knife. Definitely does a number on the looks. So this method may not be for everyone. It should also be noted that Murray uses a soft laminate which might be easier to polish.

[kennbr34]

I tend to lay back most of the main bevel to a pretty thin angle (maybe 10-13 degrees per side, and a bit convexed because it's done freehand) then put a "microbevel" on that suits the steel type and my intended use case for each knife. It's a compromise between a few things, including not doing a full regrind, keeping some durability at the edge, and still improving cutting performance. The behind the edge measurement at the top of my bevels on these kind of reprofiles is kind of huge, but it starts to lose meaning a bit because the bevel is laid back so far.

I like this way of doing things as well. I learned it in a book called The Razor Edge Book of Sharpening by John Juranitch, and he calls it a "relief angle". I think that's a little more clear than calling the primary edge bevel on a relief bevel a microbevel, because a lot of people consider a micro-bevel to be of a certain size that the one in your pic doesn't really qualify as. Also why I think the whole "behind the edge" measurement people talk about as of late is meaningless unless they're specifying how far up from the blade they're measuring. Again, going back to Juranitch's book, he suggests to keep the thickness of the blade from the edge to 1/4" up towards the spine under .020".

To determine the angle of the FFG, measure the thickness of the spine. Mark a point 1.000" down from the spine, and measure that. Now you have three dimensions of a trapezoid. Chop it up on your notepad until you have a triangle. Now solve for the unknown angles. Easy peasy.

I just did that on two Manixes. My measurements are crude: the 1" mark was measured with a ruler on and marked with a Sharpie. Nevertheless, one Manix is about 2.2 degrees per side, the other is 2.1 degrees. I also measured a Native 5, and the numbers looked consistent with the others, although I didn't do the math.

It's safe to say that using 4 degrees will get you in the ballpark. There are other variables, so trying to figure it out more precisely is a bit pointless. Sharpen to get a nice edge, not to meet an arbitrary number.

I just measure the width of the blade and plug that in as the hypotenuse, with one half of the spine forming the opposite.

So for example, my Manix 2 is 1.3" wide from the spine to the edge, and .119" thick at the same point of the spine I measured the thickness from. So my 'opposite' is .119/2 and my hypotenuse is 1.3

asin((.119/2)/1.3) * 180 / pi = 2.6 degrees

[Wandering_About]

I like this way of doing things as well. I learned it in a book called The Razor Edge Book of Sharpening by John Juranitch, and he calls it a "relief angle". I think that's a little more clear than calling the primary edge bevel on a relief bevel a microbevel, because a lot of people consider a micro-bevel to be of a certain size that the one in your pic doesn't really qualify as. Also why I think the whole "behind the edge" measurement people talk about as of late is meaningless unless they're specifying how far up from the blade they're measuring. Again, going back to Juranitch's book, he suggests to keep the thickness of the blade from the edge to 1/4" up towards the spine under .020".

That's a good way of explaining it, and better terminology to me.

[LeeARB]

This is the only knife I've thinned out. I used Harbour Freight diamond plates freehand.

Not the prettiest but it cuts like a dream.

I did the same thing with my Cold Steel AD-10 that was stupid thick behind the edge. Haven't worked up to trying it on my Spydercos yes. They aren't that bad.

[Josh Crutchley]

I did the same thing with my Cold Steel AD-10 that was stupid thick behind the edge. Haven't worked up to trying it on my Spydercos yes. They aren't that bad.

I figured since I'll never sell it why not make it cut better. One day this summer it will get a full regrind.

[LeeARB]

I did the same thing with my Cold Steel AD-10 that was stupid thick behind the edge. Haven't worked up to trying it on my Spydercos yes. They aren't that bad.

I figured since I'll never sell it why not make it cut better. One day this summer it will get a full regrind.

My AD-10 is my outdoor all purpose multitool. Chop, baton, pry, whatever comes along. Ugly is fine.

My Sage 1 Maxamet is too good looking for my meager skill level. It's a user, but I'm really enjoying how it looks as is.

[Bolster]

Has anyone here done a regrind on a slow-speed or cooled belt grinder, rather than on stones? Isn't that how pro re-grinders and/or knife makers do it?

[sal]

Hi LeeARB,

Welcome to our forum.

sal

[Josh Crutchley]

Has anyone here done a regrind on a slow-speed or cooled belt grinder, rather than on stones? Isn't that how pro re-grinders and/or knife makers do it?

I've reground some cheap knives on a Harbour Freight 1x30. Working on a Bryd Cara Cara right now but the weather is crap here. I don't have a shop so I just work in front of my shed in the spring/summer.

[Brock O Lee]

I like to convex them to reduce the thickness behind the edge. Some are done freehand, some with the help of the Edge Pro and freehand.

This Caly 3 on top was done freehand. It took a lot of time and patience to blend the edge bevel seamlessly with the spine. It is perhaps too much effort for most knives.


The Tuff I did partly on the Edge Pro, partly freehand. Lay the blade flat on the table, set the EP as low as it can go, and cut away the bevel shoulder, but leave some meat at the edge and don't go all the way to the apex. After the bulk of metal was removed, I blended the 2 new shoulders freehand to form the convex. The edge is about 18-19 dps, with a 20 dps micro bevel.



This Military had a nice convex too, until I recently chipped it on hidden steel reinforcing while cutting off an old suitcase handle. It now has a thin V-bevel at 15 dps.



Another option is to get a knifemaker to regrind it.

[LeeARB]

I managed to completely reshape and convex an Ontario Rat 2 in D2 with a HF 1x30. Best I can tell I went slow enough to not damage the heat treat, but I wouldn't do it on anything of value. My AD-10 was done by hand and took several hours to convex.

It was worth the effort in both cases. Convex edges suit me, but I haven't tried anything really thin behind the edge.