Back bevel: Shiny, rough, or doesn't matter?

[jsveiga]

My Spydercos came with the "sharpening lines" in the back bevel.

When first aggressively resharpened, I made the back bevel mirror-shiny.

Then I read someone say that the original "sharpening lines" made cutting better (maybe some kind of "ginsu" effect?).

So for experimenting only, I tried a quick pass moving the blade "backwards" with the edge perpendicular to the movement, at 20 degrees on a coarse stone (coarser than the brown triangle) (back bevel is 15+15). Running the nail on the edge, I could feel it was not a smooth slide as before, and although the blade could slice paper quite well, as expected push-cut paper was horrible.

With the smooth edge I had noticed that depending on the material being cut, the start of a delicate slicing cut was somewhat "delayed" as the blade got no immediate "bite" - so I was even tempted to leave this "micro serration" there, but as this made splitting hair unpredictable (and this is one of my "must-have" features :rolleyes :) I didn't.

I then ran the back bevel (15+15) through the coarse stone, trying to bring back the original sharpening lines, and went through the Sharpmaker's brown, fine and ultrafine stones only for the microbevel (20+20), then a light strop with green compound - so the edge is again smooth and has a shiny line, although the back bevel is "coarse".

It is clear that the edge can be left smooth or "toothy" depending on the blade usage (push cut vs slicing, material being cut, etc), but is there a logic for the back bevel? Or is it a matter of aesthetics only?

(sorry if this has already been discussed; on a quick search through the forum I could not find it)

Thanks!
Joao

[kbuzbee]

Aesthetics. Shiney is pretty.



Ken

[jsveiga]

Thanks Ken,
oh, well, back to the Sharpmaker then (I also like shiny better :o )

Aesthetics. Shiney is pretty.



Ken

[Evil D]

I believe the difference in bite that you're experiencing is a result of the actual edge being polished and not the bevel itself. That's where you're losing bite, not from the polish/scratch pattern on the bevel. Most of the sharpening junkies on here prefer to polish the bevel, but many of them (us) also go back and put a toothier micro bevel on at a higher angle so you get the toothy bite and the shiny bevel at the same time.


Then you post pics on forums and show off :D

[Holland]

I polish the bevel, then use a lower grit for the microbevel to give it a toothier edge

[chuck_roxas45]

I believe the difference in bite that you're experiencing is a result of the actual edge being polished and not the bevel itself. That's where you're losing bite, not from the polish/scratch pattern on the bevel. Most of the sharpening junkies on here prefer to polish the bevel, but many of them (us) also go back and put a toothier micro bevel on at a higher angle so you get the toothy bite and the shiny bevel at the same time.


Then you post pics on forums and show off :D

This one is a pretty important step. :D

[SQSAR]

I believe the difference in bite that you're experiencing is a result of the actual edge being polished and not the bevel itself. That's where you're losing bite, not from the polish/scratch pattern on the bevel. Most of the sharpening junkies on here prefer to polish the bevel, but many of them (us) also go back and put a toothier micro bevel on at a higher angle so you get the toothy bite and the shiny bevel at the same time.


Then you post pics on forums and show off :D

+1. Being one of the aforementioned sharpening junkies I think a polished back bevel not only looks good, but does promote a longer lasting and easier cutting blade in general (completely non-scientific opinion)

Also: Pictures are always cool.

[razorsharp]

Pics are very important

[Lo/Rez]

That's a thing of beauty.

[Cheddarnut]

Pics are very important

Pre steel junkies take note: This Will Be What You Are Forced To Eat When Addicted To Spyderco.

[razorsharp]

Tastes terrible :p looked nice

[jsveiga]

I believe the difference in bite that you're experiencing is a result of the actual edge being polished and not the bevel itself. That's where you're losing bite, not from the polish/scratch pattern on the bevel. Most of the sharpening junkies on here prefer to polish the bevel, but many of them (us) also go back and put a toothier micro bevel on at a higher angle so you get the toothy bite and the shiny bevel at the same time.

Thank you Evil D, yes, I first experimented roughing up the edge only, then I roughed up the back bevel and polished the edge again. Now I'll go back to all polished.
With the toothier edge I noticed that slicing soft toilet paper worked, but with the smooth one, the TP crumples in front of the edge, which then just slides. Splitting hair with the toothier edge had random results though, whereas with the polished one always works.
I've seen so many gorgeous pictures here that I'm quite ashamed of posting my humble edge images...

[jsveiga]

+1. Being one of the aforementioned sharpening junkies I think a polished back bevel not only looks good, but does promote a longer lasting and easier cutting blade in general (completely non-scientific opinion)

I think that makes sense.

With a rough back bevel, there is more metal surface exposed to the elements, and lots of micro grooves for salt and other corrosion-promoting contaminants to hide from a quick swipe-on-the-pants cleaning. So it would be one more reason for polished back bevels - specially with ZDP-189, M4 and such.

The smooth surface should also promote less friction when cutting (on the other hand the rough one would stick less to the subject being cut, depending on its characteristics).

[Evil D]

Thank you Evil D, yes, I first experimented roughing up the edge only, then I roughed up the back bevel and polished the edge again. Now I'll go back to all polished.
With the toothier edge I noticed that slicing soft toilet paper worked, but with the smooth one, the TP crumples in front of the edge, which then just slides. Splitting hair with the toothier edge had random results though, whereas with the polished one always works.
I've seen so many gorgeous pictures here that I'm quite ashamed of posting my humble edge images...

Nah don't be shy. I'll be the first to admit that good photography is a big part of it. I have yet to polish a bevel to a true zero scratch mirror finish..I'm just too lazy but they polish out well enough to see a clear reflection in the bevel.

As for toothy vs. polished edges, I don't think one is technically better than the other, it just depends on what your intended use is. The toothy edge may not split hair as well but it will likely slice most materials better. Think about how you use your knife and what you cut the most and tune your edge accordingly.

[bpeezer]

As for toothy vs. polished edges, I don't think one is technically better than the other, it just depends on what your intended use is.

This. Right now I have a knife with 0.5 micron finish in my right pocket, and a knife with 120 grit finish in my left pocket. They both do really well for their intended use. Honestly I don't know which one I like better, I think the consistent scratch pattern on 120 grit is actually really attractive.



Please excuse my cell phone camera photography :o

[jsveiga]

Ok, I don't feel they're up to this forum standards (pics and edges) but here they go :o

When going back to shiny this morning I first reset the 15+15 rough back bevel and the 20+20 polished microbevel with my cheapo kitchen-variety stone of unknown grits (double side), which nevertheless eats ZDP-189 with gusto. I leaned the stone against the Sharpmaker's triangle stones for 15+15 degrees, and used the less coarse side (yet much coarser than SE's brown stone).



Then I went through Sharpmaker's "Coarse", Fine, and Ultra Fine stones (all 15+15), and then stropped with green Dialux compound using an old Handycam shoulder strap (I have no leather strop), for this mirror back bevel and edge (I did not make a 20+20 microbevel this time). I tested it splitting a hair (I must declare in fairness that I have to hold the hair from both ends, and that the hair is 50% japanese, so it is thicker than an average blond hair).

The curved reflexions of the caliper's 25/1000in scale lines make my inability to keep a steady angle in the Sharpmaker very evident :o



These are the used tools; sorry for the clutter; I wanted all in the same picture: Sharpmaker, double-sided unknown material kitchen knife stone, dialux green compound bar and Handycam shoulder strap, Mitutoyo caliper (just used for the pictures), and microscope (used for examining the edge).



Thanks for the replies!

[jsveiga]

This. Right now I have a knife with 0.5 micron finish in my right pocket, and a knife with 120 grit finish in my left pocket. They both do really well for their intended use. Honestly I don't know which one I like better, I think the consistent scratch pattern on 120 grit is actually really attractive.

Thank you bpeezer. I think it's a good excuse for me to start carrying two knives too! :)

[vtvman]

The curved reflections are almost impossible to avoid when sharpening by hand. Due to all the variances they come out slightly convexed. The only way to get them straight or a perfect v edge is with a guided system. Nonetheless your edge is very nice jsveiga!

[anagarika]

Nice pics and edge !

[Evil D]

That edge looks excellent IMO, nothing to worry about.

I also find some beauty in a perfect machined/brushed looking bevel, but I prefer the contrast between a satin/brushed blade grind and the polished bevel the most. At times I don't bother polishing my bevel at all, it just depends on if I have the time and what I'm doing with the knife. Right now my 20CP Para 2 has a 20 inclusive back bevel that isn't currently polished, but it has a 30 degree edge bevel that is polished fairly reflective. It's kind of ugly but I'll get around to polishing the whole thing eventually.