Blade Steels and Zero Edges?

[David Mary]

How often do you grind blades to a zero edge? With what kind of stock thickness, blade profile, blade width, intended usage? Which steel do you use for it, and how hard do you want your blade to be to support such an edge?

The reason I ask is because I recently ordered some 1/8" thick AEB-L from Rob in Alberta, made a chef's knife for a co-worker, then had Rob heat treat it to RC 61-62. The ground the blade to a zero edge, and it behaved as a laser in the kitchen!

Also, as I was grinding, post heat treat, I clumsily dinged the heel of the blade into the aluminum wheel of my 2 x 42, while running a 1 x 42 belt. The result was a roll, not a chip, at RC 62, which was able to be mostly removed by the scotchbrite belt. This proved to me how tough AEB-L is, even at thin geometries and fairly high hardness. Quite exciting! But I would love to know what other stainless steels, especially more wear resistant ones, people have had zero grind success with, as well as the questions in the first paragraph. Thanks so much!

Thanks!

P.S. I used the search function before posting, and came up empty.

 

[Stacy E. Apelt - Bladesmith]

A zero edge is just a grinding term, meaning the edge is as thin as possible when ready for sharpening.
In practicality a Zero Edge is any bevel that ends in less than .003" edge thickness.

I take most kitchen blades to this edge in grinding/sanding, and then add the secondary bevel in sharpening at 10 DPS. If the edge is actually sharp when ground, I slightly blunt it to make sanding and handle work safer. I bet more knifemakers have been accidentally cut by a knife that hasn't been finished yet than by one they have finished and sharpened.

 

[Kali4nia]

First big cut I got was sanding at a thin edge. Didn't realize it was getting sharper...

 

[Sando]

A zero edge is just a grinding term, meaning the edge is as thin as possible when ready for sharpening.
In practicality a Zero Edge is any bevel that ends in less than .003" edge thickness.

I take most kitchen blades to this edge in grinding/sanding, and then add the secondary bevel in sharpening at 10 DPS. If the edge is actually sharp when ground, I slightly blunt it to make sanding and handle work safer. I bet more knifemakers have been accidentally cut by a knife that hasn't been finished yet than by one they have finished and sharpened.

Stacy, when you grind that thin do you flip the blade over at some point? In other words the belt is traveling away from the edge instead of into it?

 

[KNelson]

Stacy, when you grind that thin do you flip the blade over at some point? In other words the belt is traveling away from the edge instead of into it?

I’ve done this a few times and with HT’d blades I’ve been able to grind as normal “edge up”, for annealed steel either way the edge seems to roll or becomes very toothy (did this be accident).

 

[David Mary]

Thanks Stacey. So that being said, which types of knives, blade steels, and hardness would you all go so thin with? Thanks.

 

[samuraistuart]

I would stick with steels like 1084, 80crv2, 1095, w1, W2, 52100, O1, AEBL, and even A2. They are capable of very very fine grain structure, high hardness....and because of their very small carbides and low carbide % they are tough as well.

 

[David Mary]

Stuart, thank you very much for the great info, and your knives on your site look beautiful! Lots of thin edges, I see!

 

[Stacy E. Apelt - Bladesmith]

Thanks Stacey. So that being said, which types of knives, blade steels, and hardness would you all go so thin with? Thanks.

AEB-L, any good carbon steel ( as Stuart pointed out), and my favorite - S35VN. Hardness is somewhat a personal choice, but with modern metallurgy and better HT methods Rc 63-64 blades with stable edges are possible. I usually point out that hardness isn't the whole story, or we would make knives out of glass or tungsten carbide.
I do my S35VN blades (and most knives) at Rc 61-62, now. I know I could push them higher, but the edge life - sharpness - toughness balance is just right at that hardness for me.

Years back, most of us used to do knives at RC 58-60. Knives above that were considered too chippy and broke too easily. Commercial blades at that time were around Rc 56 ( or less). This is why a "steel" could be used to sharpen a kitchen knife. All it was doing was taking the very thin rolled wire edge and straightening it out. Try using a steel on a RC 64 blade and you will get nothing.

 

[David Mary]

Very interesting, thanks again.

 

[DevinT]

Two other factors to consider is the type of grind and the heat treat. Straight razors have very thin grinds appropriate for their function, competition choppers have an almost full flat grind and a convex edge and are quite thin. Some knives have full convex grinds and are ground to zero but have a little extra support at the edge.

The harder the blade, the keener and easier they are to sharpen. Depending on the knife, use the maximum hardness for the application.

Lots of good steels out there, the finer grained with smallest carbides will hold the smallest sharpening angles.

Hoss

 

[Willie71]

Have a look through this thread: https://www.bladeforums.com/threads/call-for-charpy-toughness-samples.1548360/

This is Larrin’s project on testing blade steels for toughness. Steels that maintain high toughness at high hardness in general make very good kitchen knives.