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Disadvantages to convex grind?
- Thread starter 19-3ben
- Start date
- Joined
- Apr 24, 2009
- Messages
- 662
Oh you got me there
now I get it.
- Joined
- Mar 22, 2014
- Messages
- 5,358
There's just a ton of misinformation and mysticism on both side of the argument.
In the end,
Shape meets function.
Some tasks, a convex grind is better suited, some not.
It not the grind, its the user application.
Dont get lost in hype and ego haha
As far as sharpening goes. Keep it simple
Make a convex edge at the desired angle then blurr the lines that distinguishs the new secondary bevel and primary and Shazam!
Beautiful full convex grind.
In the end,
Shape meets function.
Some tasks, a convex grind is better suited, some not.
It not the grind, its the user application.
Dont get lost in hype and ego haha
As far as sharpening goes. Keep it simple
Make a convex edge at the desired angle then blurr the lines that distinguishs the new secondary bevel and primary and Shazam!
Beautiful full convex grind.
- Joined
- Dec 8, 2011
- Messages
- 4,071
Nothing technical to add. Just another pic of a disadvantaged, ugly convex grind.
http://s1178.photobucket.com/user/apache7/media/apache7028/IMG_20151103_104234_zpsgiwz58hz.jpg.html]
[/URL]
http://s1178.photobucket.com/user/apache7/media/apache7028/IMG_20151103_104234_zpsgiwz58hz.jpg.html]
Wowbagger
Gold Member
- Joined
- Sep 20, 2015
- Messages
- 7,690
19-3ben,
You guys have helped me clarify what I am experiencing and attempting to convey by at first defending flat grind OVER, convex.
I suppose what cuts best for me, in the city slicker world, is
rather than
convex or flat
are
thin blades. See first photo. So
I tend to not want to mess up that thinness with a high angle secondary/edge angle (cutting angle).
In MY LITTLE PEA BRAIN I was envisioning taking that nice hard won thin edge grind and dubbing it over with round/convex sharpening habits.
What most here are recommending, at least I hope this to be the case, is keeping the edge angle the same and rounding off that awful transition from apex of secondary to the primary factory/makers bevel.
Im all for that. Thats a good idea. Better than I first thought.
All I am saying is dont mess with my/our original intended edge geometry with future edge touch ups.
I find that to be hugely useful. Case in point the last two box knives in the first photo :
The first one has that big comfortable handle and a ~1mm thickness blade and the factory grind. The second one has a super thin Original Stanley blade in it that is only .4mm thick and the shoulder (apex) of the edge grind taken off and the edge thinned out. The thin blade box knife is the best cutter here even in double wall heavy five foot long shipping boxes that contain fifty pound plus objects . . . no problem with edge longevity.
I will say I strongly suspect that all the splitting of the wood along the grain shown by Craytab could have been done with the same highly polished knives even if the actual cutting edges were completely dull as long as the basic wedge was the same. The actual cutting at the edge would come into play if one were to cut the sticks in half cross grain. But thas just one city kids view from Serendip.
The pics I post of flat mirror bevels are of my wood working blades (knives) if you will and I know from long and arduous experience learning the hard way that a few degrees makes quite a difference to edge life versus, cutting force versus work surface finish (tearing out hunks of wood rather than producing a flawless surface) and that any rounding just confuses the issue at the least and stops the blade from cutting at all or makes it at least unpredictable at worst.
These woodworking blades are sharpened on a jig and really are very flat bevel. I wouldnt go back to guessing and hand sharpening for the world though I can do it readily enough. A lot of these photos I already have and to capture the flatish hand sharpened edges on my knives with my iPod touch is pretty tedious. I think the basic philosophy transfers pretty well for me so I use the old photos I have.
Visually I prefer the flat mirror cutting bevel because it is so rare, makes a more striking flash and glint and being more of a machinists bent than a sculptors bent I prefer and am fascinated by really flat surfaces. See photo of my surface plate . . . one of my prize possessions.
So you see 19-3ben, it is partly a mind set as well as practicality.
I am embarrassed to say I dont use my KNIFE sharpening jig(s) much be cause it sucks so bad for small knives. I am hoping Santa will bring me an Edge Pro Apex for Knife Stuff Unwrapping Day . . . er . . . I mean . . . .Christmas.
That is as long as he isnt reading this and I dont Pssss him off too much from all this flat bevel talk.
I will say that flat facets tend to be the most attractive . . . case in point all the flat faceting that goes on with precious stones such as diamonds and rubies etc.
It isnt just me.
Come on . . . are you going to tell this chorus line they arent pretty ?
You guys have helped me clarify what I am experiencing and attempting to convey by at first defending flat grind OVER, convex.
I suppose what cuts best for me, in the city slicker world, is
rather than
convex or flat
are
thin blades. See first photo. So
I tend to not want to mess up that thinness with a high angle secondary/edge angle (cutting angle).
In MY LITTLE PEA BRAIN I was envisioning taking that nice hard won thin edge grind and dubbing it over with round/convex sharpening habits.
What most here are recommending, at least I hope this to be the case, is keeping the edge angle the same and rounding off that awful transition from apex of secondary to the primary factory/makers bevel.
Im all for that. Thats a good idea. Better than I first thought.
All I am saying is dont mess with my/our original intended edge geometry with future edge touch ups.
I find that to be hugely useful. Case in point the last two box knives in the first photo :
The first one has that big comfortable handle and a ~1mm thickness blade and the factory grind. The second one has a super thin Original Stanley blade in it that is only .4mm thick and the shoulder (apex) of the edge grind taken off and the edge thinned out. The thin blade box knife is the best cutter here even in double wall heavy five foot long shipping boxes that contain fifty pound plus objects . . . no problem with edge longevity.
I will say I strongly suspect that all the splitting of the wood along the grain shown by Craytab could have been done with the same highly polished knives even if the actual cutting edges were completely dull as long as the basic wedge was the same. The actual cutting at the edge would come into play if one were to cut the sticks in half cross grain. But thas just one city kids view from Serendip.
The pics I post of flat mirror bevels are of my wood working blades (knives) if you will and I know from long and arduous experience learning the hard way that a few degrees makes quite a difference to edge life versus, cutting force versus work surface finish (tearing out hunks of wood rather than producing a flawless surface) and that any rounding just confuses the issue at the least and stops the blade from cutting at all or makes it at least unpredictable at worst.
These woodworking blades are sharpened on a jig and really are very flat bevel. I wouldnt go back to guessing and hand sharpening for the world though I can do it readily enough. A lot of these photos I already have and to capture the flatish hand sharpened edges on my knives with my iPod touch is pretty tedious. I think the basic philosophy transfers pretty well for me so I use the old photos I have.
Visually I prefer the flat mirror cutting bevel because it is so rare, makes a more striking flash and glint and being more of a machinists bent than a sculptors bent I prefer and am fascinated by really flat surfaces. See photo of my surface plate . . . one of my prize possessions.
So you see 19-3ben, it is partly a mind set as well as practicality.
I am embarrassed to say I dont use my KNIFE sharpening jig(s) much be cause it sucks so bad for small knives. I am hoping Santa will bring me an Edge Pro Apex for Knife Stuff Unwrapping Day . . . er . . . I mean . . . .Christmas.
That is as long as he isnt reading this and I dont Pssss him off too much from all this flat bevel talk.
I will say that flat facets tend to be the most attractive . . . case in point all the flat faceting that goes on with precious stones such as diamonds and rubies etc.
It isnt just me.
Come on . . . are you going to tell this chorus line they arent pretty ?
Last edited:
- Joined
- Jun 16, 2003
- Messages
- 20,201
90% agreement.
We have members doing a given task with a "zero bevel" (AKA "Scandi") and others with a secondary bevel and other with a convex grind. Why the hostility and personal attacks? I think you hit it: "hype and ego." Can't feel more unless someone else is less.
Wowbagger
Gold Member
- Joined
- Sep 20, 2015
- Messages
- 7,690
T'anks
Blush
Careful there . . .
in the woodworking world there are those ON THE OTHER SIDE
who will call you a crazy and attempt to demonstrate all you need is a coarse swayback stone or just rub the blades on the side walk.
I've had endless "fun" arguing with their ilk.
As I some times admit, even to my self, I work wood just so I have something to sharpen.
But I don't try to make a living from my woodworking . . .
oh dear no.
For those folks wanting to play around with this stuff on a guided rod system like the Lansky, 2 observations...
1) I find that being aggresive in establishing a back level at a smaller angle is a way to move towards a convex edge. I often put on a 17 dps back bevel and a 20 dps cutting bevel when repairing an edge for EDC or kitchen use. For work in the shop, I go blunter at 20 and 25.
2) Thomas, the owner of EdgePal, often posts to the Maintenance forum. He notes that you can create a convex edge by bending a guide rod downward. This will make the angle steeper near the rod and shalllower toward the end. As you move the stone from end to end, you create a radiused edge. I use a bent Lansky rod to create a 17 to 20 dps convex edge.
More info on the EdgePal here:
http://www.edgepal.com/english/forest-17907916
1) I find that being aggresive in establishing a back level at a smaller angle is a way to move towards a convex edge. I often put on a 17 dps back bevel and a 20 dps cutting bevel when repairing an edge for EDC or kitchen use. For work in the shop, I go blunter at 20 and 25.
2) Thomas, the owner of EdgePal, often posts to the Maintenance forum. He notes that you can create a convex edge by bending a guide rod downward. This will make the angle steeper near the rod and shalllower toward the end. As you move the stone from end to end, you create a radiused edge. I use a bent Lansky rod to create a 17 to 20 dps convex edge.
More info on the EdgePal here:
http://www.edgepal.com/english/forest-17907916