Recreating the factory edge on a Sebenza 25

[kwakster]

Yesterday one of the Chefs i sharpen kitchen knives for on a regular basis decided to treat himself to a brand new Sebenza 25 from a well known Dutch knife shop.
As many here know the Sebenza is a beautifully designed & manufactured knife, and the model 25 may very well be considered the current king of the hill in the series.
Sadly the factory edge on the first example the Chef got to handle was just plain blunt, and upon inspection it turned out that the other 4 or 5 Sebenza's 25 that the shop had in stock suffered from a comparable bluntness.
To cut a long story short: in the end the Chef liked the knife so much that he just bought the least blunt one, while the shop assistant promised to contact CRK to see if the other knives could be sent back.

Anyway, today the Chef contacted me to ask if i could do something about the edge on his knife.
The first thing i noticed about the blade on his model 25 is that it seems to be ground a hair thinner behind the edge compared to previous Sebenza's 25 that i've handled and sharpened, and that as a result the edge bevels were quite narrow, even with a measured inclusive edge angle of 35 degrees.
The second thing i noticed (with my Victorinox loupe) was that the edge reflected light almost along it's entire length, and i couldn't even cut a piece of copy paper with it.
Now i think that the edge wasn't completely apexed, but with only my loupe to judge by i'm not 100 % sure.

In a conversation with the owner and also because the knife is brand new we came to the conclusion to give it a new edge that would resemble the factory edge as much as possible, and to make it seem as best as i could that nothing was done to the knife.
First i removed the blunt apex of the factory edge by cutting several times into a silicon carbide stone, after which i gave it a completely new edge with an experimental Rubber Wheel with 230 grit diamond powder.
Finally i removed the tiny burr with a Paper Wheel with 1 micron diamond compound.
The new edge again measures 35 degrees inclusive from heel to tip, survives a few cuts into my laminated test block without visible damage, and can still easily treetop the hair on the back of my hand.
I think the owner will be happy when he comes to collect his knife tomorrow morning.

Before sharpening:









After sharpening:

[enki_ck]

Excellent work as alqays.

[Mike, Lord of the Spammers!]

Beautiful work mate

[Zed]

At the price these are i would want it razor from new  great job on getting them as they should be kwakster 

[ducttapetech]

Nice work!

Nate

[Aloha]

At the price these are i would want it razor from new  great job on getting them as they should be kwakster 

I'd agree this knife should have been very sharp from factory.  The owner will be super stoked to get this knife with an amazing edge. 

I am curious tho, why that particular angle from Sebenza I wonder?  Also very interesting about the apex being along the length of the blade.  I also wonder why stropping or "finishing"  isn't done on these "customs". 

I've come to feel that 20-22 degrees per side is a good angle for what I use my knife for.

Is there any conclusion on your part as to a good "standard".     

[toolguy]

The model 25 that is shown in the OP's post is not a "custom",it is a standard factory production knife.

Reeve changed the blade geometry on the model 25 compared to the model 21's.

Perhaps this may offer an explanation.

"Large Hollow Grind Technology—the first blade to feature this new grind that blends the best of hollow and flat grinds."

http://chrisreeve.com/Sebenza-25

[kwakster]

Is there any conclusion on your part as to a good "standard".     

With my personal EDC knives i mostly go for as thin as possible but thick enough.
As an example: this is currently one of my EDC knives, an older saber/flat grind Spyderco Endura ZDP-189 that i turned into a saber/hollow grind with my Tormek.
The ZDP-189 steel is about 65 HRC and can handle an edge bevel of 17,5 degrees inclusive strengthened with a microbevel of around 30 degrees inclusive in my use:



Most well hardened modern high carbide steels can handle an edge angle in the region of 25 to 30 degrees inclusive, if necessary strengthened with a microbevel.
This is what i do on most Spyderco's, Benchmades, Striders, etc.

When sharpening (expensive) knives for others i also take esthetics and owner's wishes into account, which sometimes leads to larger edge angles (to keep bevels on thicker blades more narrow visually)