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Basic three step knife sharpening : destress the edge + shaping + finishing the apex

Posted by CliffStamp 
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 15, 2012 08:00PM
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me2
I'm not sure what you mean by consistent, but watch the video using the 24 grit stone. The knife and stone are both moving all over. I don't really thing exact angle control is that important. If it were, we'd all have to use jigged sharpeners. I think "just getting close" will work fine, but the edge will look pretty rough.

Hmm, now I'm more confused. I've watched the video several times. I've been trying to duplicate what Cliff does in the video. Just isn't working for me.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 16, 2012 12:54AM
There are a few likely problems, one is that the low grindability of the steel is causing an issue and that you are having to do too much work to reach an apex that you are either not reaching an apex or when you do it is over stressed from too heavy pressure.

Take a fairly inexpensive knife, grind a 10 degree relief bevel until the edge stops reflecting light, then greatly reduce force and grind at 15 degrees. It is also vitally important that you keep in mind this is a very trivial thing, it isn't hard/complicated and you can easily do it.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
December 16, 2012 05:36AM
I'm working down a very used kitchen knife using this method. So far, it will just shave hair on my arm. I've destressed and apexed twice, and there are still some chips and dings in the edge. This knife has never responded well to my water stone, so we'll see if I can get it this way.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 03, 2013 01:52AM
Ok, after a first try beginners luck success, I've not been able to get this to work nearly as well on any other knife. Keeping at it.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 03, 2013 04:36AM
Is it unusual to have to go through the destressing step a couple of times for a new knife? I got a new Gerber Paraframe from the in-laws for Christmas and had to sharpen it today. I destressed, removed the flat at the edge, and back honed on the 220 grit stone 3 times before refining the microbevel on the 1000 grit side would yield an arm shaving edge.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 03, 2013 04:48AM
It is common for initial edges to be damaged, I normally don't pay attention to the edge until it has been sharpened at least 3-4 times, up until then all you could be seeing are the results of the power buffing/stropping.
me2
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 03, 2013 05:28AM
I know I had to form a full burr, cut into the stone, and reform it twice to get an arm shaving edge off the 1k stone. At this stage the RADA knives were catching hair above my skin, but both were old and heavily used/sharpened.
Quote
me2
Is it unusual to have to go through the destressing step a couple of times for a new knife? I got a new Gerber Paraframe from the in-laws for Christmas and had to sharpen it today. I destressed, removed the flat at the edge, and back honed on the 220 grit stone 3 times before refining the microbevel on the 1000 grit side would yield an arm shaving edge.

Hi,
Can you describe what back honing is?

================================================
<<Les Garten>>

Always carry a flagon of whiskey in case of snakebite, and furthermore always carry a small snake
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 25, 2014 02:01AM
Usually refers to sharpening at a lower angle than the apex bevel, either to add a small transition bevel or to remove a higher angle microbevel added during burr removal.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 25, 2014 02:06AM
In the method I am describing back honing is when you hone at the original edge angle to minimize the effect of any additional edge bevels which are used to minimize a burr. For example :

-sharpen the edge at 10 dps
-1-3 very light passes at 30 dps to remove the burr
-back sharpen at 10 dps to minimize the very heavy 30 dps bevel

As you get more familiar with the steel and stones being used you will find there is less need to use heavy bevels to minimize the burr and thus less need of back sharpening.
Quote
CliffStamp
In the method I am describing back honing is when you hone at the original edge angle to minimize the effect of any additional edge bevels which are used to minimize a burr. For example :

-sharpen the edge at 10 dps
-1-3 very light passes at 30 dps to remove the burr
-back sharpen at 10 dps to minimize the very heavy 30 dps bevel

As you get more familiar with the steel and stones being used you will find there is less need to use heavy bevels to minimize the burr and thus less need of back sharpening.

Thanx, I am learning a ton here about sharpening.

What is the difference between deburring as described above, and microbeveling?

================================================
<<Les Garten>>

Always carry a flagon of whiskey in case of snakebite, and furthermore always carry a small snake
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 25, 2014 03:48AM
Using very high angles in deburring is an application of micro-bevels, but they have other uses such as just strengthening an edge, or rapid sharpening when a full bevel grind would take too long.
Hi Cliff,

I'm only learning about sharpening, so this thread has been enormously interesting. I'm curious: Do your reservations about stropping apply to convex edges as well? Does stropping make sense in their case as long as the strop is only abrading the edge and not bending it back and forth — or is that bending inevitable?

Thanks.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 25, 2014 05:58PM
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Teague
Hi Cliff,

I'm only learning about sharpening, so this thread has been enormously interesting. I'm curious: Do your reservations about stropping apply to convex edges as well? Does stropping make sense in their case as long as the strop is only abrading the edge and not bending it back and forth — or is that bending inevitable?

Thanks.

Hi Teague,

I don't think the bending back and forth is necessarily inevitable...if you don't apply enough force to do it, it won't happen, but this is very hard to do on a soft backed substance, especially if you're doing significant strokes (which then also loads your strop with metal...another bad thing). And if anything I would think it's almost easier to do with a convex edge as it may be harder to judge whether you are hitting the actual edge/apex. As a result, people may push harder in order to get to it, or raise the blade more, both of which would make it more likely and also increase your apex angle.

Additionally, depending on the stropping abrasive it's not likely to abrade as quickly, beyond simple "touch ups" and so people may get into a hurry and apply for force and make the issue worse again.

Just some thoughts. Hopefully I don't have them wrong.

_______________________________________________________________________________________________

Always in search of a good choppa'
Hrm. So short of sharpening on a slow belt, what's the best way to sharpen a convex blade? Wouldn't using stones introduce all sorts of inconsistencies — or do they somehow average out to something uniform?

Thanks again. And apologies for the very basic questions.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 26, 2014 12:42AM
Shape the convex however you want then put a micro bevel on the edge. Is one option, or.
I have a few convex blades I sharpen them on sandpaper sitting on a piece of tee shirt cotton as a backer. I can comfortably shave with them off 2500 grit paper (wet). I will strop on paper loaded with 1 micron diamond and I toss it after one or two knives. I have found you need to hold the blade at a shallower angle than what you want as the finished edge. The last few passes elevate the blade angle 2 or 3 degrees and make super light passes on whatever grit paper you are using. If you have a steady hand and light pressure these can be edge leading ( honing passes) not stropping passes.. This will give the best results. Hope this helps. Making a good convex edge ( stable and sharp) is more difficult than a v edge.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 26, 2014 11:55AM
Mark's advice is good. It's not so much avoiding stropping because of the problems it poses, but being aware of those problems and doing what you can to minimize them as Mark does in his technique...avoiding excessive use of the same strop to avoid dealing with loading, holding hte blade at a shallower angle somewhat to keep lots of pressure off the very apex, etc.

You can also do a convex with stones though. Here is a video on doing it with axes, but the same applies with knives...you work your way down the primary to the apex increasing the angle each time, and you end up with a convex. As for how uniform it is...well, it's one of those practice things. AT first it may not look that great or smooth, but you can get pretty damn good for it





_______________________________________________________________________________________________

Always in search of a good choppa'
Cliff, how do you sharpen and maintain your convex edges?
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 27, 2014 03:13AM
Benchstone, even on the convex blades with recurved grinds.

All of my blades have a very light convex arc to the grind because of the wear in the stones and the light angle slop that comes in hand sharpening. Depending on the blade this will range from 2-4 dps at the very edge over the top of the grind angle.



This is a very nice slip joint from cKc (Kyley), it has one continuous bevel and if you just did the trig on that bevel from top to bottom it would be 4.5 dps. However at the very edge, under 0.010" thick, the curvature starts to increase and it is 7.5 dps at the apex.

This however is not an intentional curve, it is sharpened flat to the stone, it just picks up that curve from the wear in the stone and the slop in hand sharpening. If I wanted to increase the curvature I would :

-put more force in sharpening closer to the edge bevel instead of towards the spine

will pick up 1 to 1.5 dps

-let the stone wear more

will pick up 2-3 dps easily

-lightly lift the blade after the initial shaping

Do whatever is easiest for you.

The simplest way to learn is take some very easy to grind blade (cheap stainless kitchen paring knife) and just practice apexing it. Don't be concerned about getting it sharp, just do the shaping stage. Sharpen it with a micro-bevel.

In time you will get to the point where it will be sharp off of the shaping and the need for micro-beveling will decrease - but you are likely to find that it is very useful for maintenance and ease of sharpening on hard to sharpen blades.
Thanks very much. Very interesting. I've watched quite a few of your videos, but I can't immediately recall one of you sharpening a convex blade. Is there one out there?

Should I assume you consider the sandpaper-and-foam-backing setup as ineffective — or even damaging — as a strop? The mechanics seem to be the same.

Final question: If I understand correctly the concaving of the stone seems to serve a purpose in maintaining the convex of the blade. So I should steer clear of DMT and the like?

Thanks again, very much.



Edited 1 time(s). Last edit at 01/27/2014 04:53AM by Teague.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 27, 2014 10:33AM
Hi Teague,

Here is Cliff sharpening the convex and recurved Hossom Forrester.




I don't really worry about sharpening convex (I just do a flat bevel and then knock the shoulder off for a half assed convex if I really get motivated), but I have used the recurve advice and it works well.

_______________________________________________________________________________________________

Always in search of a good choppa'
cKc
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 27, 2014 01:21PM
cliff, is that photo above the burnt ruined one? it looks short on edge steel.

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It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 27, 2014 04:33PM
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cKc
cliff, is that photo above the burnt ruined one?

The not-a-knife one? No, it isn't that one.

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Teague
Thanks very much. Very interesting. I've watched quite a few of your videos, but I can't immediately recall one of you sharpening a convex blade. Is there one out there?

All of them are as I don't use jigs/true-flat stones.

Quote

Should I assume you consider the sandpaper-and-foam-backing setup as ineffective — or even damaging — as a strop? The mechanics seem to be the same.

It can be done, but I just have a few issues :

-you are edge trailing which is going to make burr formation likely and removal non-trivial

This is why there is so much discussion of burrs and how to cut them off on cardboard, wood, or stropping etc. .

-it is expensive in the long term

I can wear out an actual stone in a year and that would be a LOT of sandpaper, but I sharpen a fair amount

-you have to use water for health reasons

This means most solutions are not practical, what you need to use is a high density foam which is water resistant and wet-dry sandpaper and keep it wet.

Doing that, if you watch this video :





the bevel on that knife is convex with a micro-bevel. While the video is long, there is only about 2 minutes of sharpening and this is a complete sharpening, the edge is cut off before the sharpening starts.

I can't see how you could achieve that kind of efficiency on a sandpaper based system and that brick is free and would last you a lifetime. However I do recommend unless you want a challenge to use an actual stone.

On a side note, I get fairly constant messages from people who claim that the reason there is a long delay between when I "finish" sharpening the knife and I show it on the paper is that I give it off screen to someone who actually sharpens it as it is impossible to sharpen a knife as noted in the video. The amusing thing about this is that you can clearly see the knife to my side the entire time as I just lay it down and pick it up.

Oh internets.

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Final question: If I understand correctly the concaving of the stone seems to serve a purpose in maintaining the convex of the blade. So I should steer clear of DMT and the like?

It depends on what you want to do and how you want to do it. There are three ways that can be done as noted in the above. You can do it with a true-flat stone like the DMT's, I have done it but it is more challenging - though offers more control than using a natural wearing soft stone. Kyley has talked about this when he speaks about how he doesn't simply create a convex grind using the slack belt section but uses a platen as he has more control over the curvature.

The best way to figure it out is to just get a cheap benchstone, you can get them for $2 at any flea market and not much in other stores. Then take a cheap kitchen knife that you don't mind using up and do a full convex grind on it. Then start a thread here and post about your results and have some discussion. I guarantee it isn't nearly as hard as you might think it is, in fact I know it isn't because hillbillies around here do it all the time.
Thanks, everyone.

Kyley, I've seen your very persuasive arguments for convex blades. How do you sharpen and maintain yours?

Thanks again.
cKc
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 29, 2014 10:13AM
My methods of doing convex are pretty simple.. use the belt grinder for any major work, and use the stones, diamonds, sandpaper, strop etc for maintenance of the apex until it becomes overly thick, then spend about 15 seconds on a grinder to thin it a bit.

if you really want to maintain a zero convex, then the best way I find is SC wet/dry sandpaper on a fairly firm backing (never soft mousepaddy stuff.. ) just hard leather, hard rubber, a phone book.. etc.


I will micro bevel my convexes all the time for simplicity until it becomes too thick and reblend again rather than trying to maintain a full sweeping convex over the primary every time I hone.. its much easier to hone a couple of thou of steel than it is an entire side of a knife.

Here is how I was showing people to do it 4 years ago





the main thing to note in that video is where I'm using the strop with a lot of force and a fair number of strokes I'm not honing the apex.. I'm using it as a fine polishing medium to polish the side of the blade and barely contacting the apex. when I get to the very end I am actually lightly honing the apex.


another 4 year old video.. how I explain people use a strop to maintain convex (or anytihng)





these videos were made for customers who literally have trouble sharpening *anything* full stop and the goal is just to get the knife to cut stuff without concern for finesse, or longevity etc because if you can hone it, you can hone it again.

I also use my smooth hones to maintain the edges.. I dont think it matters. what matters is the totality of the geometry of the knife, rather than a few microns here and there at the apex.

----------------------------------------------------------------------
It's not Cliff, its Dr Stamp
#kebabstickcut, it's a thing - make it happen
Thanks very much, Kyley. A lot of good information here.
This may be of interest to some of you... Particularly post # 13495 and 13545. Clearly stropping has a positive effect on a freshly sharpened edge and would not, according to my extremely limited knowledge of physics, weaken the metal (because there would be no bending back and forth).

I strop my edges to maintain them in between sharpenings. But I do it with the understanding that my edge retention is not going to be as long/good aand that I am giving up some of the toothiness that I love. When I go back to sharpen I do destress the edge (thanks to Cliff).

On a side note, one thing I've been doing is: if I notice that an edge has chips/damage then I will overly destress the edge, aka clean it up and erase all the chips with my stone perpendicular to the edge. Then I can sharpen like normal without having to do several "sessions"... Make sense? Is there any negatives to doing it this way?
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 30, 2014 03:14PM
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razoredgeknives
On a side note, one thing I've been doing is: if I notice that an edge has chips/damage then I will overly destress the edge, aka clean it up and erase all the chips with my stone perpendicular to the edge. Then I can sharpen like normal without having to do several "sessions"... Make sense? Is there any negatives to doing it this way?

This is exactly how Cliff recommends you do it if you are desiring to completely remove the chips. But if you look at his Rex121 thread and his post last night about the 10v knife, he doesn't always do that as it does shorten the life of the blade. He will often leave the chops and simply round them out so they aren't chips jagged and let them disappear over several sharpenings.

_______________________________________________________________________________________________

Always in search of a good choppa'



Edited 1 time(s). Last edit at 01/30/2014 03:40PM by C Amber.
Re: Basic three step knife sharpening : destress the edge + shaping + finishing the apex
January 30, 2014 03:26PM
Yes, essentially I will look at the functional performance of the blade. For example most large blades have damaged tips/belly because that is the area that often contacts the ground. I want it to be functionally sharp as that is a sweeping/draw point contact for soft vegetation, but there is no functional loss in having 5% of the edge damaged.

However if it is a craft knife which cuts paper, fabrics, etc. then a small chip can damage the material and the entire edge has to be perfect. Similar for knives used for wood carving, a small irregularity can lead to obvious flaws in the surface finish of the wood so again the entire edge has to be free of defects.

Just take a look at the practical influence and grind accordingly, the less damage you remove the longer the lifetime of the blade. If you look at my Fiskar's you can see that there are many large chips in the edge, that edge will never be fully clean because it does a lot of axe work and bark is dirty.
Sorry, I forgot to post a link lol

[www.wickededgeusa.com]
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