Best config for good convex edge?

N

nutria_man

Joined
May 7, 2008
Messages
93
hi all,
Is the slack belt the best way to get a consistent convex edge?

Are there any other attachements you folks use for creating a convex edge?
Thanks
 
Aww jeez...you threw in the word , "consistent"....that makes it a tougher question.

Yes and no.

What really matter is the type of convex edge you want.

DO you want a flat ground blade with a convex edge...or a tru full convex.

Both need to be set up properly for them to hit your "consistent" requirement.

A full convex edge, ground with only a slack belt and no platen behind the belt to support the shape, can be extremely tricky because the belt will flex with any irregularities in either belt tension, belt shape, platen shape, your hand pressure and probably several other things I am forgettign to mention.

Grinding a slack belt can put a beginnner in a tizzy pretty fast. That 2 inch gouge becomes pretty deep if you have a hand dominance issue...

And maintaining good grind lines can becaome tough for perfect symetry.

Have I confused you yet?

Wayne Goddard has done a good job of explaining this...have you read his books.

If you are just starting out, I highly recommend flat grinding your blades and then putting a convex edge on, until you are comfortable with increasing the bevel to include the entire blade.

It is easier to maintain a consistent symetry from side to side and the you can teach yourself how to roll the edge without ruining a lot of blades.

Somebody else better chime in here...casue I don't think I did a good job of explaining
What kind of blades are we talking here?

BTW~ What kind of blades are we talking?

Shane
 
The rotary platen for the KMG works quite well for convex grinds. That is what Scott Gossman uses, IIRC. I flat grind before heat treating and then if I am doing a Moran style knife, I convex it the last little bit of the way on the rotary platen,
 
There is a way I cam up with (probably thought of already) of getting easily repeatable convex grinds. Flat grind your blade until the edge thickness is where you want it to be, IE thicker for a more steep convex thinner for a more subtle convex, then slack belt from there.
 
jdm61 said:
The rotary platen for the KMG works quite well for convex grinds. That is what Scott Gossman uses, IIRC. I flat grind before heat treating and then if I am doing a Moran style knife, I convex it the last little bit of the way on the rotary platen,
Click to expand...

You know the rotary platen with an adjustable depth guide might be the trick. hummmm
 
I use to use the rotary platen doing the complete convex grind but found if I flat grind first, it's not only faster but the geometry is much better. I flat grind about 70% then use the rotary for about 30% to finish the grind. After HT, I complete the blade on the rotary platen.
Scott
 
I should add that finishing the edge is done with the slack belt which IMO is the best way to get a true convex edge.
Scott
 
Gossman Knives said:
I should add that finishing the edge is done with the slack belt which IMO is the best way to get a true convex edge.
Scott
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True dat. I used to have a problem with flatspotting the tip until I starting using 1 inch belts and pulling the tip away when it got halfway across the belt. Very few issues now. I sharpen on the part of the slack belt right up next to the whell so it flexes the minimum amount and tend to roll over less.
 
Sam Salvati said:
Also a way to get an AMAZING kickass sharp edge too.
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yes indeed. :D I finish my edges with a plain medium scotchbrite, then a fine scotchbrite loaded with compound on the slack belt. Produces a wicked edge.
Scott
 
Gossman Knives said:
yes indeed. :D I finish my edges with a plain medium scotchbrite, then a fine scotchbrite loaded with compound on the slack belt. Produces a wicked edge.
Scott
Click to expand...
I'm still knocking the wire off with a couple of light swipes on a fine stone with Cool Tool as lubricant and then using my 4 sided strop stick to finish it up.
 
a piece of plywood with some soft foam on it and then some sandpaper held on top is a good way to put a convex EDGE on a blade, the foam flexes pretty evenly if the pressure applied is equal, i know several makers who use this to sharpen blades with excellent results.

Also, it's a really cheap way of doing it so you can always have a go and then decide you don't like it without wasting big bucks on tooling
 
ONeill said:
question . why the Moran convex edge if the knife is not used for chopping ?
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Because it works.:D Whe he was in Troy at the hammer-in, Kevin Cashen was giving a little talk on edge geometry, etc, and he remarked that the "secondary bevel" edge that we are so familair with is merely a work/time saving technique developed in modern times. He said that pretty much all of the better old blades that he has handled either had a convex edge, a "zero" grind or some combination/variation thereof.
 
ONeill said:
question . why the Moran convex edge if the knife is not used for chopping ?
Click to expand...

Adding to jdm61 comment, it stays sharper longer, is stronger and is easily resharpened with inexpensive sharpeners. Convex edges require less material to be removed when resharpening. Stropping on leather with added compound will maintain the edge for quite awhile.
Scott
 
Gossman Knives said:
Adding to jdm61 comment, it stays sharper longer, is stronger and is easily resharpened with inexpensive sharpeners. Convex edges require less material to be removed when resharpening. Stropping on leather with added compound will maintain the edge for quite awhile.
Scott
Click to expand...

do you have a picture of a profile of an edge such as the Moran?

I always thought all edges eventually have a secondary edge? Unless you are grinding the entire edge every time you sharpen.. would not a secondary edge result?

Sorry.. not that familiar with the Moran edge.
 
Gossman Knives said:
yes indeed. :D I finish my edges with a plain medium scotchbrite, then a fine scotchbrite loaded with compound on the slack belt. Produces a wicked edge.
Scott
Click to expand...

Gossman , I like the idea of the fine scothbrite with compound . Sounds as if that would create the microscopic saw tooth edge as opposed to a polished edge .

Nutria-man , you are correct .
once the convex edge is resharpened on a flat stone ( depending on the angle ) you have created a secondary edge .
 
ONeill said:
Gossman , I like the idea of the fine scothbrite with compound . Sounds as if that would create the microscopic saw tooth edge as opposed to a polished edge .

Nutria-man , you are correct .
once the convex edge is resharpened on a flat stone ( depending on the angle ) you have created a secondary edge .
Click to expand...

Ok. I thought with a coined name like that .. there must be something additional added...I googled and did not find anything unique.

thanks
 
I do Moran edge for all the knives I make, I've noticed even for kitchen knives the moran edge does the job well and stays sharp longer...
 
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