Shawn Hatcher
Well-Known Member
Hmmm. I don't think I've ever used "simple" and "flat grinding" in the same sentence!
can someone please walk me through convex grinds?
- Thread starter SHOKR
- Start date
Hmmm. I don't think I've ever used "simple" and "flat grinding" in the same sentence!
SHOKR
Well-Known Member
lol
that actually gives me hope, Shawn.
i just figured what i do so far is straight forward flat gridning, no recurve, several bevels(altho i tried that few times with no success) convex, etc.
I watched Bill Moran develop a full convex grind on an 8 inch wheel, grinding with the edge down in the early 80's. The convex grind was beautiful, perfectly centered and uniform. This is very easily the toughest way, but he learned the technique before we had the quality belts now available that allow us to grind with edge up facing into the direction of the belt traveling downward.
Shawn Hatcher
Well-Known Member
That's amazing, Ed. Thank you for sharing.
Shokr: The most essential aspect is a fresh belt and a light touch. My initial grinding is done on a wheel, then I go to a slack belt and carefully blend from edge to spine. My first grinds are done on a 36 grit Aluminum Oxide belt, immediately followed by a 220 grit belt to remove all scratches.
It takes practice, if you were in my shop I could have you doing it well in a day. I learned by practicing, and have learned how to coach new comers how to do it after teaching many makers and learning how to teach from them. I wrote it up in Blade a few issues ago and some liked the explanation. It is not as easy to do as the flat grind, but in my opinion it is well worth it when it comes to performance. The convex grind provides the strongest blades and if done right are a joy to use.
It takes practice, if you were in my shop I could have you doing it well in a day. I learned by practicing, and have learned how to coach new comers how to do it after teaching many makers and learning how to teach from them. I wrote it up in Blade a few issues ago and some liked the explanation. It is not as easy to do as the flat grind, but in my opinion it is well worth it when it comes to performance. The convex grind provides the strongest blades and if done right are a joy to use.
rhinoknives
Well-Known Member
ED,
Thanks for the quick walk through on your technique, Do you know what issue of Blade Mag this article was in?
I would love to read it for a refresher course of your thoughts and practices.
I am currently planning on modifying a Convex Rotary platen made by Ron Frink of KMG fame. There needs to be more clearance on the left side to make full use of the Tank trap rotary. Hope to have it done by New Years!
Laurence
www.rhinoknives.com
Thanks for the quick walk through on your technique, Do you know what issue of Blade Mag this article was in?
I would love to read it for a refresher course of your thoughts and practices.
I am currently planning on modifying a Convex Rotary platen made by Ron Frink of KMG fame. There needs to be more clearance on the left side to make full use of the Tank trap rotary. Hope to have it done by New Years!
Laurence
www.rhinoknives.com
SHOKR
Well-Known Member
Ed Fowler:231970 said:
Thanks a lot Ed
I probably never would have thought of these things on my own
I wouldve loved to be in your shop
The issue no. Or date would be nice as Laurence mentioned
Also if you dont mind me asking, why wheel then convex instead of flat then convex? I mean is it personal preferance or affects performance
Would the 220g shift after 36 work on hollow or flat grinds too? Or gradual step up would be better?
Thanks again, Ed
Josh Dabney
Moderator
Ed Fowler- GREAT to see you posting here at Knifedogs !!!! Without the free sharing of info from those of you with the years and the miles we'ld all still be flint knapping our blades so your contribution to the forum is greatly appreciated.
I'll first say that convex edges are one of the easier techniques to master so have no fear of that. Of course there is a learning curve but it'll be short and relatively painless
There are some things to consider that can shorten your curve though.
You can get a great result just going at it with a slack belt. This however will be the slowest method that uses the most abrasives. IMHO the way to go is to first rough-in your convex free hand with a series of flats to set up the geometry that you're after and finish up by blending those into a smooth convex with the slack belt.
I think it's important to note that the covex has geometry. It can be a fat convex or a thin convex or anywhere inbetween. It can be a true zero ground convex right to a sharp edge with no sharpening bevel whatsoever. It can be zero ground with a micro-bevel. And it can be super fat and thick at the edge still with a large sharpening bevel.
It's up to you to decide the goal with YOUR convex geometry.
I'll get a pic in a bit of two kitchen knives I've made to accurately display this point about geometry.
Deciding what geometry to use is another discussion entirely but I will suggest that there is NO substitute for testing your own knives thoroughly. Not destructive testing but using testing that lasts long enough to go through several re-sharpenings at minimum. This is going to tell you more about your methods than a gazillion of our typed words
Your own process will also have an effect on what makes sense to do. When I do my convex edge I don't want to risk adding any super deep scratches to my blade that'll cause me nightmarish blade finishing so I do it all on a 220 belt.
Again you'll have this down in no time at all.
I'll add one more thing. I have a Rotary Platen and love it for this purpose. However, there is nothing magical about it and I don't achieve an end result any different than what I got before I had it. What it does do is save me time especially in blending the top of the convex into the flat but a bit of effort hand sanding will do the same thing.
Take care,
Josh
Without the free sharing of info from those of you with the years and the miles we'ld all still be flint knapping our blades so your contribution to the forum is greatly appreciated.I'll first say that convex edges are one of the easier techniques to master so have no fear of that. Of course there is a learning curve but it'll be short and relatively painless
There are some things to consider that can shorten your curve though.
You can get a great result just going at it with a slack belt. This however will be the slowest method that uses the most abrasives. IMHO the way to go is to first rough-in your convex free hand with a series of flats to set up the geometry that you're after and finish up by blending those into a smooth convex with the slack belt.
I think it's important to note that the covex has geometry. It can be a fat convex or a thin convex or anywhere inbetween. It can be a true zero ground convex right to a sharp edge with no sharpening bevel whatsoever. It can be zero ground with a micro-bevel. And it can be super fat and thick at the edge still with a large sharpening bevel.
It's up to you to decide the goal with YOUR convex geometry.
I'll get a pic in a bit of two kitchen knives I've made to accurately display this point about geometry.
Deciding what geometry to use is another discussion entirely but I will suggest that there is NO substitute for testing your own knives thoroughly. Not destructive testing but using testing that lasts long enough to go through several re-sharpenings at minimum. This is going to tell you more about your methods than a gazillion of our typed words
Your own process will also have an effect on what makes sense to do. When I do my convex edge I don't want to risk adding any super deep scratches to my blade that'll cause me nightmarish blade finishing so I do it all on a 220 belt.
Again you'll have this down in no time at all.
I'll add one more thing. I have a Rotary Platen and love it for this purpose. However, there is nothing magical about it and I don't achieve an end result any different than what I got before I had it. What it does do is save me time especially in blending the top of the convex into the flat but a bit of effort hand sanding will do the same thing.
Take care,
Josh
Josh Dabney
Moderator
Here's a tale of two convex edged kitchen knives I've made to show the different geometries.
The blade on the left is a few years old and one of my first convex edges. Notice how big the sharpening bevel is. This is not a product of many many sharpenings wearing the edge back to the thick part of the flat but a product of the convex being way too fat for my sharpening angle. Due to this convex geometry the act of sharpening on a stone has removed much of the convex that was originally there.
The blade on the right is only a couple months old and the sharpening bevel shows up in this close-up shot with the camera but it's so small it's hardly noticible without close study of the blade.
These two blades are the same steel type with similar grinds and HT but they cut very differently.
Please ignore the lack of care ! I always wash and dry after use but my wife tends to leave them laying in puddles on the counter, soaking in pans of water, or cuts stuff without washing the knife afterwards. Oh the humanity of all I know.... but of course I forgive her for her sins against the blade steel gods
Of course I do still love me some carbon steelunk:
-Josh
The blade on the left is a few years old and one of my first convex edges. Notice how big the sharpening bevel is. This is not a product of many many sharpenings wearing the edge back to the thick part of the flat but a product of the convex being way too fat for my sharpening angle. Due to this convex geometry the act of sharpening on a stone has removed much of the convex that was originally there.
The blade on the right is only a couple months old and the sharpening bevel shows up in this close-up shot with the camera but it's so small it's hardly noticible without close study of the blade.
These two blades are the same steel type with similar grinds and HT but they cut very differently.
Please ignore the lack of care ! I always wash and dry after use but my wife tends to leave them laying in puddles on the counter, soaking in pans of water, or cuts stuff without washing the knife afterwards. Oh the humanity of all I know.... but of course I forgive her for her sins against the blade steel gods
Of course I do still love me some carbon steel
unk:-Josh
rhinoknives
Well-Known Member
Ed Fowler- GREAT to see you posting here at Knifedogs !!!!
I'll first say that convex edges are one of the easier techniques to master so have no fear of that. Of course there is a learning curve but it'll be short and relatively painless
There are some things to consider that can shorten your curve though.
I think it's important to note that the covex has geometry. It can be a fat convex or a thin convex or anywhere inbetween. It can be a true zero ground convex right to a sharp edge with no sharpening bevel whatsoever. It can be zero ground with a micro-bevel. And it can be super fat and thick at the edge still with a large sharpening bevel.
Deciding what geometry to use is another discussion entirely but I will suggest that there is NO substitute for testing your own knives thoroughly. Not destructive testing but using testing that lasts long enough to go through several re-sharpenings at minimum. This is going to tell you more about your methods than a gazillion of our typed words
Your own process will also have an effect on what makes sense to do. When I do my convex edge I don't want to risk adding any super deep scratches to my blade that'll cause me nightmarish blade finishing so I do it all on a 220 belt.
Again you'll have this down in no time at all.
I'll add one more thing. I have a Rotary Platen and love it for this purpose. However, there is nothing magical about it and I don't achieve an end result any different than what I got before I had it. What it does do is save me time especially in blending the top of the convex into the flat but a bit of effort hand sanding will do the same thing.
Take care,
Josh
Josh,
I agree that doing a convex grind is fairly easy, perfecting this grind takes a bit longer!!
Shokr,
The convex grind Josh is referring to that has very little no sharpened edge is referred to as a Bullet Grind. Like a spritzer or military rifle bullet that curves out to the end. The Japanese incorporate these into the culinary knives in a 50/50, 70/30 or 80/20 and one sided. Mastering this grind takes awhile but once you see how this cuts and you see how this can cut circles easier than flat or hollow. You will be completely impressed.
Laurence
www.rhinoknives.com
The change frrom 36 grit to 220 negates the need for a bunch of belts in between 36 and 220 grit. I used to work down progressively from 36 to 60 to 110 to 220 then one day discovered it was not needed.
I can't remember the time I did any hand sanding on the sides of a blade.
I use the rubber wheel to hog down to the approximate geometry I seek to achieve in the final grind. Like any other grinding method it takes a little practice.
I wish you luck, there is only one rule - Enjoy what you are doing!
I can't remember the time I did any hand sanding on the sides of a blade.
I use the rubber wheel to hog down to the approximate geometry I seek to achieve in the final grind. Like any other grinding method it takes a little practice.
I wish you luck, there is only one rule - Enjoy what you are doing!
SHOKR
Well-Known Member
Ed Fowler- GREAT to see you posting here at Knifedogs !!!!
exactly that! i'm just not good with words
Josh, you're not making it simple... AT ALL lol
i think i get what you mean now, photos are worth thousand words after all
there was a blade, one of the first i ground on the new grinder, tried two bevels on it, near tang full flat and the front one about half way up the blade, i kept ruining it so i decided to give convex a try (not a good one, just see how it grinds) did it on the slack, and now trying vinegar etching it as well
the process seemed simple enough, but of course its different when i am trying and trying to get a goot SYMMETRICAL product thanks Josh