What do you take your kitchen knives down to before convexing?

M

Maelstrom78

Joined
Sep 21, 2013
Messages
1,574
I've been I guess worried about edge toughness after some donkey used a super thin santoku I made to hack into bones and took out a 1/2 dime sized chip.

That baby was thiiin and sliced like a dream but I just used my flat platen the whole time. I would guess I had the edge down to .005 or under before I sharpened it at 20 degrees inclusive.

I want to start using the slack portion of the belt to convex closer to 0. Am I thinking about this correctly for chef type knives?

Maybe get them down to .005-8 or something and then carefully convex on the slack belt at 400 grit?

Sound about right?
 
For an 8" chef, I'll often rough grind to where it's full flat with the edge at .040" and the spine .090", heat treat, and then use the platen to grind the lower third into a mild even convexity, ending near zero at 400 grit gator, then getting to zero when hand sanding. Then I sharpen at about 10 degrees per side, which only takes a few passes since the edge is so thin.

This seems a little thick perhaps, but i find that to promote food release there does need to be a tangible bit of convexity. This results in a blade that will still slice very well, is a bit more robust, bends some food off (not all) and is still usually in the neighborhood of 6-7 oz. total including handle.

For AEB-L, I heat treat at full thickness, then flat grind to the above, or .090" and .030", then convex to zero.
 
Thank you so much Salem. I'm leaning towards a more (relatively speaking) robust convex edge like you are describing. Especially as I am thinking again of selling a few off and I want them to be able to withstand some ham-handedness.

But you use the platen for convexing and not a slack or rotary platen? I've done that on my disc grinder and then blended it out so I should be able to do that on the belt as well.

What you are doing sounds very good and I'll try that out. I have another 7" santoku and an 8" western style chef to finish grind so I can get some practice on those in short order. These are AEB-L as well. I'm going to start grinding the AEB-L post HT as well like many of you do. I can see what ppl say about it grinding almost nicer after HT. Especially as I have my wet grinding setup back up and running.

Thanks again!
 
The last 2 kitchen knives I finished, I convexed when the edge was about .015 for the 10" blade and .010 for the 7" blade. There is not a whole lot of convexing going on there. They are super slicey but sticking can be more of an issue. I think what Salem is describing is something I want to try next.
 
It will be interesting to see what responses you get. It's always cool to see what other makers are doing and how. But I would say that there are many ways to grind a chef's blade, and it depends on what you want to do with it.
if you want a generalized blade, then leave some meat on via a convex grind, or thicker flat grind. But there is nothing wrong with the laser blade you created. The problem with it was that the user used it inappropriately, as you noted.
Lasers and hefty blades both have their purposes. :)
 
I do more or less what Timos does. I take the edge to about .010" and then use the rotary platen to convex it to zero. This convexes down the last 1/2" or so. I add a final micro-bevel at about 10 degrees per side.
 
I'm intrigued by the rotary platen. I wonder how hard it would be to make a simple two wheel slack platen?

So I would need a tool arm, a couple of wheels and the sandwich them between two "U" shaped 1/4" plates?

Have the wheels like 6" apart? I would be slack belting up to probably 2.5" width knives on the thing. Hmm I'll have to cogitate on that some.

Oh and Stacy or anyone: Do you use your rotary platen to do the microbevel as well? I've been using my flat platen to about 400 grit and then finishing by hand.

Thanks!
 
Last edited:
It really doesn't matter much on the micro-bevel. Sometimes it is on a stone, sometimes the slack belt, sometimes the rotary platen. The best is on a stone.

I wouldn't waste time or money trying to build a negative curvature platen. If you want to convex the simple way, just put a layer of the graphite platen liner on a flat platen. It will work great for convexing. It will dish out on its own in use and be even better.
 
Last edited:
I find convexing works real nice on the portion of belt running horizontal before the belt even gets the the platen, slower speed and I like to use the gator belts for this.
 
I convex with the edge towards me, belt running from spine to edge. But it's not really running towards me as I generally stand to either side of the grinder when doing it.
 
You must log in or register to reply here.
Back
Top