Sebenza edges

I've sharpened quite a few Sebenza's for others, and how i sharpen them is based on both personal experience and user feedback.
On older ones i've learned that the lowest angle i can reprofile them to lies around 35 degrees inclusive, and that i have to keep the edge finish rather coarse to still have quite good edge retention.
On newer ones i can lower the edge angle to around 30 degrees inclusive, and i also can refine the edge more, yet still have good edge retention.
Other people may have other ideas, but this is what i've found to work well.

Yesterday i did this regular Sebenza from 2005 in S30V steel, which is the favorite folder of a professional hunter.
The old factory edge was kept more or less sharp by him with stropping only, and the edge angle measured 35-40 degrees inclusive on the straight part and well over 40 degrees inclusive from the belly to the tip.
I reprofiled the edge to an even 35 degrees inclusive from heel to tip on my Rubber Wheel covered with 230 grit diamond powder (covered in wax to prevent any damage due to overheating), and only removed the burr with the Tormek leather wheel coated with 1 micron diamond compound.
This removes the burr gently but efficiently, while at the same time leaving the scratch pattern intact as much as possible to preserve bite (something i specifically aim for)
The Rubber Wheel has a tiny amount of "give" in it's surface which provides for an ever so slight convexity in the new edge, and the use of diamonds makes sure that the vanadium carbide particles in the steel are cleanly cut.
The resulting coarse edge both favors the S30V steel type and the actual use it will see in the hands of the hunter, and it's treetopping sharp with lots of bite.

No "before" pics this time (i forgot), but below are the result pics i also sent to the owner.

suomi70: This one came out a little less than perfect as i couldn't get the point exactly in the middle this time, but things like that are dependant on the "form of the day", as it's all freehand work.
On these blown-up pics it looks worse than in real life though.

The reason why i started this thread was because i was wondering if Sebenza owners on this forum had anything to contribute regarding the edge retention of their pre- or post 2013 Sebenza models, as somewhere during that year CRK seems to have decided to harden their blades to 59-60 HRC instead of the usual target hardness of 58-59 HRC.

On the Dutch forum there are at least a few owners who were less then satisfied with the edge retention of their beloved Sebbies, especially when the edge angle was taken down to +/- 30 degrees inclusive, an angle that can be considered a good rule of thumb when sharpening most modern knife steels.
Spyderco for instance specifically target their edges to come out at that angle after factory sharpening.

Also found this thread from 2012/2013 on Bladeforums where members talk about having their Sebenza blades rehardened, apparently with good results:

http://www.bladeforums.com/for…a-blade-for-heat-treating

This was posted today on Bladeforums by Anne Reeve:

This is a moment where CRK has to take a humble "cap in hand" and apologize for a failure of communication between our technical side and our customer service side. Yes, around mid-2013, the RC hardness on all the folding knives (Damascus excluded) was changed from 58-59 to 59-60. Our guarantee cards, brochure and website did not reflect that change. We are not happy about this lack of communication and are in the process of updating the relative published material.

Chris made the decision after reviewing the performance of S35VN at both hardnesses. He has always been a proponent of a slightly lower HRC to ensure shock absorbency and ease of sharpening. When he was convinced that blades at 59-60 would perform extremely well and meet all of his criteria, the change was gradually implemented. Bear in mind this is a possible spread of only 3% and a likely change of only 1% in the hardness and not a major change at all.

Anne

These also belong in this thread:

A new edge for a Sebenza 25

Recreating the factory edge on a Sebenza 25

Based on feedback from CRK owners i would definitely say that the new heat treatment protocol is a noticeable improvement.

This Rockwell C Differential Comparitor shows the hardness change in percentages:

http://bessex.com/forum/showth…id=287&highlight=Rockwell

According to this the difference between a "pre-mid-2013" Sebenza with a 59 HRC blade and a "post-mid-2013" Sebenza with a 60 HRC blade is a 4.9 percent increase in hardness.

And if you compare a "pre-mid-2013" Sebenza with a 58 HRC blade with a "post-mid-2013" Sebenza with a 60 HRC blade then the difference would be a 9.8 percent increase in hardness.