Cutting sharpening choils

[Jason B.]

Sorry, but no, it's not a fact, and you have no idea how hard I'm pressing on my stones. What is a fact is that repeatedly stressing a 1-2mm section of anything is going to cause that very small area to wear faster than the surrounding area. That is incontrovertible.

I'll take your word for it..

Can we see some pictures ? It's kind of hard for me to believe that you can do this without damaging the edge of the stone .

Pictures of what? I have sharpened tens of thousands of knives, thousands of sprint run Spyderco, super hard custom knives, my own knives, etc. I have no one I need to prove my skill to, especially on this forum.

 

[eveled]

Yes rhino that is what I do.

I use the angle grinder and a very delicate touch to remove the excess then sharpen on a diamond stone. With the Ricasso pressed to the side of the stone.

 

[eveled]

Sorry, but no, it's not a fact, and you have no idea how hard I'm pressing on my stones. What is a fact is that repeatedly stressing a 1-2mm section of anything is going to cause that very small area to wear faster than the surrounding area. That is incontrovertible.

FWIW I agree.

 

[Spey]

Wow, what a group of choilers we have here ... (joke in friendship friends).

RE: wearing edges of your stones comments above

I think a lot of the comments here, related to wearing out stone perimeters/edges from removing this minuscule (1/32" - 3/16" long) section of the blade, are forgetting about how applied pressure on the stone is distributed across an area of contact whilst they are sharpening, and how changing the contact area effects stone contact pressure between stone & steel based on surface area of contact.

I understand how easy it is (been there done it myself), when focused on a small area that is giving you the finger, to remember that when the area of contact decreases (less stone to steel contact area) the pressure exerted on the remaining contact area is increased, and to compensate by reducing applied pressure to stone proportionally. Quick Example: area of pressure on a 1" stone with 100% contact is reduced to only 1/4" the contact pressure is amplified at least 4x (5lbs becomes 20lbs).

Example:
If a stone is 1" wide with 5lbs of pressure (applied pressure to stone) on the flat/straight portion of a blade is moved to an area of less contact (belly section, this section just fwd of ricasso we are discussing, etc.), that same 5lbs of pressure (applied pressure to stone) becomes concentrated greatly (pressure exerted on contact area stone to blade). When stone to blade contact area is reduced, the user needs to be smarter than the tool being used and decrease the pressure (applied pressure to the stone) accordingly. This type of magnified pressure (reducing contact area without reducing applied pressure) will strip diamonds off a DMT plate FAST, and/or will wear the edges of a stone (typically this is done at the beginning of a reprofile with your coarsest stone in a progression and the main part of the stone will be abraded both during the remaining reprofile process which also includes the belly section where the center part of the stone receives the majority of contact pressure. Also, dressing the stone(s) appropriately is part of the over maintenance of your tools.

Inversely, this IS why we sharpen our knives to an apex (to increase edge contact pressure : user applied pressure ratio).

 

[rhino]

Am I the only one who doesn't really care if there is a tiny unsharpened portion of blade near the ricasso?

 

[eKretz]

Wow, what a group of choilers we have here ... (joke in friendship friends).

RE: wearing edges of your stones comments above

I think a lot of the comments here, related to wearing out stone perimeters/edges from removing this minuscule (1/32" - 3/16" long) section of the blade, are forgetting about how applied pressure on the stone is distributed across an area of contact whilst they are sharpening, and how changing the contact area effects stone contact pressure between stone & steel based on surface area of contact.

I understand how easy it is (been there done it myself), when focused on a small area that is giving you the finger, to remember that when the area of contact decreases (less stone to steel contact area) the pressure exerted on the remaining contact area is increased, and to compensate by reducing applied pressure to stone proportionally. Quick Example: area of pressure on a 1" stone with 100% contact is reduced to only 1/4" the contact pressure is amplified at least 4x (5lbs becomes 20lbs).

Example:
If a stone is 1" wide with 5lbs of pressure (applied pressure to stone) on the flat/straight portion of a blade is moved to an area of less contact (belly section, this section just fwd of ricasso we are discussing, etc.), that same 5lbs of pressure (applied pressure to stone) becomes concentrated greatly (pressure exerted on contact area stone to blade). When stone to blade contact area is reduced, the user needs to be smarter than the tool being used and decrease the pressure (applied pressure to the stone) accordingly. This type of magnified pressure (reducing contact area without reducing applied pressure) will strip diamonds off a DMT plate FAST, and/or will wear the edges of a stone (typically this is done at the beginning of a reprofile with your coarsest stone in a progression and the main part of the stone will be abraded both during the remaining reprofile process which also includes the belly section where the center part of the stone receives the majority of contact pressure. Also, dressing the stone(s) appropriately is part of the over maintenance of your tools.

Inversely, this IS why we sharpen our knives to an apex (to increase edge contact pressure : user applied pressure ratio).

Eh, not quite. In your example, 5 pounds does not become 20 pounds (unless you are very angry perhaps). The pressure per square inch (or whatever unit you would like) will quadruple if the area in contact is divided by 4, but psi is not a straight equivalent to pounds of force. And that increase in pressure does not generally equate to cutting 4 times as fast. Nor does it mean that the hone will not wear... Even with normal pressure non-electroplated hones wear and become not-flat as dull grit particles are dislodged and come loose.

The main consideration here is that there's a large excess of material that needs to be removed from that section of most blades to straighten them out compared to the small amount that generally needs to be removed from the rest of the blade. That is what generally causes the extra wear at the corner of the hone.

I don't know about the rest of you, but I sharpen a knife to use it, not to worry about resale value or whether a knife is museum quality perfect in appearance. If you would rather sharpen your knife to a dead 90° corner instead of using a choil, that's fine too. No need to denigrate the way anybody else does it.

 

[Spey]

Eh, not quite. In your example, 5 pounds does not become 20 pounds (unless you are very angry perhaps). The pressure per square inch (or whatever unit you would like) will quadruple if the area in contact is divided by 4, but psi is not a straight equivalent to pounds of force. And that increase in pressure does not generally equate to cutting 4 times as fast. Nor does it mean that the hone will not wear... Even with normal pressure non-electroplated hones wear and become not-flat as dull grit particles are dislodged and come loose.

The main consideration here is that there's a large excess of material that needs to be removed from that section of most blades to straighten them out compared to the small amount that generally needs to be removed from the rest of the blade. That is what generally causes the extra wear at the corner of the hone.

I don't know about the rest of you, but I sharpen a knife to use it, not to worry about resale value or whether a knife is museum quality perfect in appearance. If you would rather sharpen your knife to a dead 90° corner instead of using a choil, that's fine too. No need to denigrate the way anybody else does it.

RE: "Eh, not quite. In your example, 5 pounds does not become 20 pounds (unless you are very angry perhaps). "
I am not referring to the weight being increased due to frustration (that would be additional and also multiplied by 4x in example), I am referring to the increase due to decreased contact patch stone to steel.

RE: your 1st paragraph appears to generally agree with what I wrote above (4x increase due to decreased contact stone to steel). Please let me know if my math is askew in any way that affects the results (below illustration).

Example: 1" wide stone (common guided system dimension)


The entirety of my comments relate to excessive pressure in the reduced contact patch of stone/steel being the cause of excessive wear, especially on stones referenced by many above like DMT Diamond plates, being the reason some experience this excessive wear while others do not (Jason B. & myself for example). My comment above "... forgetting about how applied pressure on the stone is distributed across an area of contact" aka exerting excessive stone to steel pressure, unknowingly.

There is a situation comparison that I would also bring into the conversation that might be a factor.
Typically when I am removing this small amount of steel from the heel of an edge, I am at a point where I have decided to keep the knife and, I am also reprofiling the bevels (so, a fair amount of work being done with a re-profiling stone including work in the belly were the reverse type of stone wear is occurring - as I referenced in previous post). My guess also common situ from Jason B. perspective (where the majority of the work being done is NOT just the removal of this small triangle).
vs.
Others, may only be matching the factory bevels (so very little stone work main blade bevels & belly, compared to a re-profile of secondary bevels), were the amount of work using only edge of stone is a greater percentage of overall work being done with stone.

Additionally, this is really only related to the most coarse stone in a progression as that is the only stone really cutting excessive amounts of steel (and that little triangle near the heal is pretty small).

 

[sodak]

I use a small diameter dremel, and a bucket of water to dunk in. The knife, not the dremel, lol. Once I buy a knife, it's mine to do as I please with. Some knives just beg for a choil, some are better off without it, IMO.

 

[Bruce Thomas]

Noticed it and going if I am going to sell your knives do I really have to take time to put the final edge on it. It is irritating I agree. CMT razor edge, why doesn’t Spyderco finish. I don’t know but I have often thought, good knife, want to buy it, do you want me to do a courtesy sharpening for you. I mean really I can take a lot of knives out of the box and sit them on a tomato and they just cut by themselves. What are you guys lazy or something. Really they are not sharpened all the way. Come on guys finish the knife all the way

 

[zephy5]

With the stock Wicked Edge stones you can't get all the way back on a knife like a PM2, the handle gets in the way. I used a small jewelers rat tail diamond file to put a small choil in mine. Just go slow and keep it parallel to get crisp edges.

 

[eKretz]

RE: "Eh, not quite. In your example, 5 pounds does not become 20 pounds (unless you are very angry perhaps). "
I am not referring to the weight being increased due to frustration (that would be additional and also multiplied by 4x in example), I am referring to the increase due to decreased contact patch stone to steel.

RE: your 1st paragraph appears to generally agree with what I wrote above (4x increase due to decreased contact stone to steel). Please let me know if my math is askew in any way that affects the results (below illustration).

Example: 1" wide stone (common guided system dimension)
View attachment 1733776

The entirety of my comments relate to excessive pressure in the reduced contact patch of stone/steel being the cause of excessive wear, especially on stones referenced by many above like DMT Diamond plates, being the reason some experience this excessive wear while others do not (Jason B. & myself for example). My comment above "... forgetting about how applied pressure on the stone is distributed across an area of contact" aka exerting excessive stone to steel pressure, unknowingly.

There is a situation comparison that I would also bring into the conversation that might be a factor.
Typically when I am removing this small amount of steel from the heel of an edge, I am at a point where I have decided to keep the knife and, I am also reprofiling the bevels (so, a fair amount of work being done with a re-profiling stone including work in the belly were the reverse type of stone wear is occurring - as I referenced in previous post). My guess also common situ from Jason B. perspective (where the majority of the work being done is NOT just the removal of this small triangle).
vs.
Others, may only be matching the factory bevels (so very little stone work main blade bevels & belly, compared to a re-profile of secondary bevels), were the amount of work using only edge of stone is a greater percentage of overall work being done with stone.

Additionally, this is really only related to the most coarse stone in a progression as that is the only stone really cutting excessive amounts of steel (and that little triangle near the heal is pretty small).

My point was more that you weren't very consistent with your terms or your verbiage. That can be confusing to people. Switching up pressure and force for instance, as well as just leaving them out entirely in some instances, can cause issues for some.

As far as arguing about whether or not people should use a small relief at the end of a blade to simplify and shorten their sharpening time, I'm squarely in the "who cares" section. For most knives I own, I don't generally want to spend time worrying about the appearance of a knife, I want it to be sharp. I don't really care if it's pretty. I also don't really care about whether someone else does want to spend their time doing that... If they do, more power to them!

 

[Gary W. Graley]

I am firmly in the camp of no sharpening choil, one of the reasons I do like Spyderco blades. Now, if a knife has such an opening at the end of the edge, what I tend to do is to grind in an angle or radius so that any material that happens to fall into that area will slide up and out onto the edge and not get hung up. Similar to what I did to my Benchmade Triage, I also hand ground down the spine into a pointy clip point, like it a lot better with that profile, the G2, well that was put on by the place my daughter bought it from many years ago for me, as I'm known by the G2 shown on the blade

IMG_6426 by GaryWGraley, on Flickr

G2

 

[Gary W. Graley]

here's a short video showing another folder that I did the same kind of radius at the start of the edge, so that the soft material did not get hung up when trying to cut it, if it still had the abrupt pointed corner, it would catch and not slice.

G2

 

[crukstrom]

Yeah, pretty much disagree with most of that about sharpening and stone wear

But here is my take on the two,

A racisso creates a stop and the sharp edge goes all the way too it, like a mora. When you add a choil you create a flat edge and large divot in the blade for material to get caught in. Try to cut any large material, animal hide, clothing, cardboard, etc and the choil eventually hangs up on the material being cut. With a racisso style you can drive the blade all the way to the racisso and because it extends below the cut it acts as a surface guide leading the cutting edge through the material.

I agree 100%. Working as a carpenter I cut all types of materials and quite often those come in rolls or sheets like plastic sheeting, roofing felt, cloth fabrics etc. A sharpening choil often hangs up in these materials and is a real irritation. As long as you only using the tip or belly then there’s is no problem but when you have to engage the entire edge, a sharpening choir sucks.