How important is the back bevel?

S

speedfan

Joined
Sep 5, 2003
Messages
390
I'd like to sharpen some of my knives to a 30 degree edge instead of a 40 degree edge. I use a Sharpmaker. How much would I lose by doing away with the backbevel and just using the 30 degree side of the sharpmaker?
 
Lose?

I think a lot of people do exactly that (go with a 30 degree inclusive). If there is anything to be lost it would be a slight bit of durability of the edge (40 degrees leaves more material to support the edge).

The only way to know and understand entirely how a 30 degree edge grind will help/impact your use is to try it.

Depending on the blade steel, you may loose a bit of TIME going to a 30, unless you have the diamond rods for your Sharpmaker....
 
Well, not worried about edge durability (given the blade properties of the knives I want to do this too) or time, but what I meant is not what do I lose going from a 40 to 30 degree edge, but what do I lose, if anything, by going from a 40 degree edge with a 30 degree back bevel to simply a 30 degree edge. The sharpmaker manual seems to suggest the back bevel is important, but it suggests a lot of things....
 
speedfan said:
Well, not worried about edge durability (given the blade properties of the knives I want to do this too) or time, but what I meant is not what do I lose going from a 40 to 30 degree edge, but what do I lose, if anything, by going from a 40 degree edge with a 30 degree back bevel to simply a 30 degree edge. The sharpmaker manual seems to suggest the back bevel is important, but it suggests a lot of things....
Click to expand...

I guess I am using poor nomenclature. I consider anything that I grind away from the knife (for the sake of "sharpening") to be the "edge". So I was referring to the edge grind being 30 degrees (no back bevel).

Once you set your edge grind to 30 degrees with no back bevel, any touch ups you want to do later will require you to either:
1. remove material along the entire edge grind (typically 1-2mm wide area of steel behind the edge), or
2. start using a higher degree angle for a back bevel (40 degrees perhaps) and then you will only remove a tiny bit of material (a fraction of a mm right at the cutting edge)

If edge durability and time are not your concerns, I can not imagine what else you could possibly fear loosing?
 
I guess I got the impression that the back bevel was doing something to make it sharper somehow, but I guess not.

BTW, thanks for the help. Now, to break out the diamond rods....
 
speedfan said:
I guess I got the impression that the back bevel was doing something to make it sharper somehow, but I guess not.
Click to expand...

It doesn't make the edge any sharper, but it makes for less resistance when cutting through material.
 
Well, it does make a difference when you're cutting through stuff. The thinner bevel helps by giving you less resistance.

The modern super steels give you 2 things. One is increased edge retention. The other is the ability to support a thinner edge (back bevel) that won't chip or roll as easily as other steels.

For example, my S90V blades have a 20 degree inclusive bevel that slices like nothing else. The same principle applies to full flat ground blades. Less resistance equates to better slicing.

:) I'm repeating. Exactly as THG said.
 
Some stuff came up and I didn't get around to doing it yet. In the mean time I got to thinking - what do you guys think about using the scissor slot for the back bevel and the 30 degree for the edge? Or is the scissor one too extreme?
 
You must log in or register to reply here.
Back
Top