Final steel thickness for chef's knife and also best practice on final sharpening.

RayJ

Member
Guys,

a newbie question, I'm on my 7th or so knife so still very new to this so please excuse the questions.

1. What is the best final thickness of the steel at the cutting edge for a chef's knife. I am using 15N20 carbon steel.
2. I'm planning to do a flat grind and was thinking of doing the final sharpening on a slack belt on my 2X72, but this is where I am confused. On a lot of YouTube video's I see a lot of people doing the final sharpening on some kind of Lanksy Style sharpening system or on stones (which I am not great at doing) Others I see use the slack belt on the grinder and seem to get good results with that. Is there a better way or a best practice way to do the final sharpening. This is my biggest issue so far in knife making. It's probably the most important part, really no point churning out beautiful looking knives that can't cut.

Any help on this would be much appreciated.

thanks

Ray
 

Taz575

Well-Known Member
I have seen chefs knives that were .020" thick at the edge and they had fat edges. .010" behind the edge is what I look for, but it will depend on the steel and grind. I have messed with Japanese kitchen knives where the edge is extremely thin, but the steel is harder and with a good cutting board, holds up well. Japanese edges are ground almost right to the edge and then have a very small bevel. I would try to do .010-.015" behind the edge and then do a shallow slack belt to get most of the edge there and then touch it up on the stones to really refine it. This will leave you with some convexing near the edge, but a small micro bevel type edge instead of doing a wide edge bevel.
 

billyO

Well-Known Member
Is there a better way or a best practice way to do the final sharpening.
Better??? The only thing I can think of is spending more time with whatever system you settle on.

The 3 methods you mention in your original post will give 3 different edge shapes.
Lansky-type systems will make a concave (hollow ground) edge, flat stone sharpening will leave a flat/chisel edge, and slack belt sharpening will leave a convex edge.
Here's a link: http://zknives.com/knives/articles/knifeedgetypes.shtml
In a very general sense, the hollow ground edge helps thicker blades have a finer/sharper cutting edge, but tends to be a little more fragile and the convex shape helps a thin blade have more edge stability/strength.
Probably the easiest to learn is the slack-belt method as this can hide some minor mistakes that are glarinlgy obvious when using flat stones. I've never used a lansky system, but they seem set up to give very consistent grinds, but if the end user doesn't have one, the first time they sharpen it they will be changing the edge shape.

I'm not sure how I would decide this if I were you. If you're making knives for someone else, it might be a good idea to see how they sharpen their knives and match your final grind to their system. If you're making them for your own use, then I'd probably choose which method is the easiest for me (or what type of equipment I have) and spend time perfecting this.
 

RayJ

Member
Better??? The only thing I can think of is spending more time with whatever system you settle on.

The 3 methods you mention in your original post will give 3 different edge shapes.
Lansky-type systems will make a concave (hollow ground) edge, flat stone sharpening will leave a flat/chisel edge, and slack belt sharpening will leave a convex edge.
In a very general sense, the hollow ground edge helps thicker blades have a finer/sharper cutting edge, but tends to be a little more fragile and the convex shape helps a thin blade have more edge stability/strength.
Probably the easiest to learn is the slack-belt method as this can hide some minor mistakes that are glarinlgy obvious when using flat stones. I've never used a lansky system, but they seem set up to give very consistent grinds, but if the end user doesn't have one, the first time they sharpen it they will be changing the edge shape.

I'm not sure how I would decide this if I were you. If you're making knives for someone else, it might be a good idea to see how they sharpen their knives and match your final grind to their system. If you're making them for your own use, then I'd probably choose which method is the easiest for me (or what type of equipment I have) and spend time perfecting this.
thank you Billy, I guess the easiest method for me like you said is the slack belt method as that is the only method Ive even been successful with. I just didn't want to be investing in this method if for some reason it wasn't good for the knife because it takes too much material off or something like that.
I basically start off with a slack belt and keep the edge up and then use a leather buffing wheel afterwards. I recently got a rubber platen which I will try using keeping the edge down and then finishing off with the leather buffing wheel.
 

RayJ

Member
Better??? The only thing I can think of is spending more time with whatever system you settle on.

The 3 methods you mention in your original post will give 3 different edge shapes.
Lansky-type systems will make a concave (hollow ground) edge, flat stone sharpening will leave a flat/chisel edge, and slack belt sharpening will leave a convex edge.
Here's a link: http://zknives.com/knives/articles/knifeedgetypes.shtml
In a very general sense, the hollow ground edge helps thicker blades have a finer/sharper cutting edge, but tends to be a little more fragile and the convex shape helps a thin blade have more edge stability/strength.
Probably the easiest to learn is the slack-belt method as this can hide some minor mistakes that are glarinlgy obvious when using flat stones. I've never used a lansky system, but they seem set up to give very consistent grinds, but if the end user doesn't have one, the first time they sharpen it they will be changing the edge shape.

I'm not sure how I would decide this if I were you. If you're making knives for someone else, it might be a good idea to see how they sharpen their knives and match your final grind to their system. If you're making them for your own use, then I'd probably choose which method is the easiest for me (or what type of equipment I have) and spend time perfecting this.
Your explanations really help!!
 

billyO

Well-Known Member
Glad to help, Ray.
I guess the easiest method for me like you said is the slack belt method
This is what I do most often. One thing I've done to my grinder that seemed to help is add pyroceramic glass to my flat platen (roundingthe top edge) and this sits ~1/4" proud of my wheels, which gives me a short slack portion that's about a 15 degree angle between the top roller and the top of my platen. All I have to do is keep the blade straight up and down to get a decent and consistent edge angle. Also, I think this short slack portion will give a more consistent angle across the whole blade than if I were to use a slack area that's between rollers that are further apart, like between the tracking wheel and the top wheel on my platen. (I hope this makes sense)
 

Sean Jones

Well-Known Member
Glad to help, Ray.

This is what I do most often. One thing I've done to my grinder that seemed to help is add pyroceramic glass to my flat platen (roundingthe top edge) and this sits ~1/4" proud of my wheels, which gives me a short slack portion that's about a 15 degree angle between the top roller and the top of my platen. All I have to do is keep the blade straight up and down to get a decent and consistent edge angle. Also, I think this short slack portion will give a more consistent angle across the whole blade than if I were to use a slack area that's between rollers that are further apart, like between the tracking wheel and the top wheel on my platen. (I hope this makes sense)
This is basically what I do as well.
 

SS369

Well-Known Member
I take my chef knives to .010 at the edge and then use a made jig on my belt grinder to set the edge with a 400 grit belt running against the platen. Takes 2 minutes.
I find it easier to follow a flat edge on final sharpening using a KME set up, if I want to refine the edge further.
 

John Wilson

Well-Known Member
Not much to say that hasn’t been said. Great advice so far. Your question falls right into that gray area where there’s no single right answer- from here on out you have to experiment to find what works best for you, the steel you use, the heat treatment of that steel, and the geometry of the knife.

In other words, it’s time to get very consistent. The first place to get consistent is the final edge thickness before sharpening. I am a firm believer in going super thin, even past the point that the knife won’t hold a great edge for very long. Why? Because it’s so easy to adjust that. Every time you sharpen a knife the edge gets thicker, because it’s a wedge. If you take an edge too thin it will only get more durable with subsequent sharpening. Now compare that to a knife that is already too thick. It only gets worse. Sooner or later you have to thin the bevel or walk your cutting edge up the bevel. Now to sharpen the knife you have to sharpen that whole giant secondary bevel you made instead of just touching up a teeny microbevel at the edge like you would on a thin blade.

I take my blades to .005 - .010 before hand sanding. Hand sanding thins that even more. I sharpen on a slack belt and finish by hand on a leather strop.

About going too thin: If it’s thin to the point of chipping out then run the knife edge against the belt point down- grind the edge flat. Then sharpen it again. No problem. We’re talking thousandths of an inch here. It is child’s play to fix an edge that is too thin for the steel or for the application. But an axe will never be a good kitchen knife.
 
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