Sebbie vs shrink wrap

J

jasonbroni

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Dec 10, 2009
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Ok - so I get my small 21 sharp enough to shave (touch up) my cheeks at work (to maintain my awesome beard) lol and s-cut news print.
Subject change - my spyderco dice and para 3 are just as sharp, but... when the dice and para 3 simply touch, graze, or even look at shrink wrap - it cuts. The sebbie can lightly pass/graze the wrap and not cut?? What the hell? Is it the hollow grind vs the flat grind? My angles are roughly the same - dice and para at 17 dps and (maybe) the sebbie is at 17 or 18?
I don't get it?? (Although I'm guessing it's the flat grind?)
What do you guys think?
Thanks in advance.
 
I found a mirror edge on my Spyderco Native made it better than a razor for cutting through shrink-wrap, it may just be the type of edge you have it on it. Perhaps you have a wire edge on it that's preventing a clean bite into the wrap and causing it to glide over it instead?
 
I've cut a decent bit of shrink wrap with sebenzas. Never had a problem.
 
Toothy vs polish level on edges?

My Mantra 2 would actually take more effort than my Large 21 until I put a toothy edge on the Mantra.
Mind you, neither took much pressure at all. But the difference was seen in bunching on the Mantra 2 and none on the Large 21.

I have since gone to a toothy edge and thinned the shoulders slightly on the (already slim) Mantra, and it is noticeably better on pallet wrap, banding/strapping material, cardboard, et al... It is paired with a Maxamet Mule for warehouse work.
 
jasonbroni said:
Ok - so I get my small 21 sharp enough to shave (touch up) my cheeks at work (to maintain my awesome beard) lol and s-cut news print.
Subject change - my spyderco dice and para 3 are just as sharp, but... when the dice and para 3 simply touch, graze, or even look at shrink wrap - it cuts. The sebbie can lightly pass/graze the wrap and not cut?? What the hell? Is it the hollow grind vs the flat grind? My angles are roughly the same - dice and para at 17 dps and (maybe) the sebbie is at 17 or 18?
I don't get it?? (Although I'm guessing it's the flat grind?)
What do you guys think?
Thanks in advance.
Click to expand...


Correct me if I'm wrong but doesn't CR convex bevel the edge ?
I call it roundyround.
You are seeing an example of why I detest this sort of "grind"/edge bevel.
I should probably qualify that with : IF over done.

Put a shallow / flat bevel grind on that puppy and try'er out. If that doesn't do it get "the thickness behind the edge" down bellow 0.020" (0.5 mm).

Another test is fresh bread. Take a stock edge from SAK or Case to a fresh bread roll and it just slides back and forth and doesn't slice.
Grind the thickness behind the bevel thinner and the sharpening angle shallower and : SSSSSsssss l l l l i i i i ce.

O'course if you plan on hammering the edge through a rock or splitting diamonds the stock edge is jusssabout right.

PS: another example stock was my Manix . . . had thirty thou behind the edge. Suuuuuucked at cutting plastic wrap off product packaging. Embarrassed me to no end in front of customers.
 
All 3 of the knives are sharpened the exact same way. I reprofiled the sebbie to (almost) the exact bevel and micro bevel as the other 2. Just as sharp. Just doesn't cut/slice as well. Maybe i just prefer flat grinds. (Sucks - cuz I could have sold the sebbie when it was fresh from the spa last month instead of using for a month and reprofiling it.)
 
jasonbroni said:
All 3 of the knives are sharpened the exact same way. I reprofiled the sebbie to (almost) the exact bevel and micro bevel as the other 2. Just as sharp. Just doesn't cut/slice as well. Maybe i just prefer flat grinds. (Sucks - cuz I could have sold the sebbie when it was fresh from the spa last month instead of using for a month and reprofiling it.)
Click to expand...
That leaves thickness behind the edge.

Also are you ABSOLUTELY sure you reprofiled down to the very apex ? ? ?
Is there any chance you rebevelled but that the final micro part of the edge is the stock / wider angle / rounded profile ? ?
 
Wowbagger said:
That leaves thickness behind the edge.

Also are you ABSOLUTELY sure you reprofiled down to the very apex ? ? ?
Is there any chance you rebevelled but that the final micro part of the edge is the stock / wider angle / rounded profile ? ?
Click to expand...

Another thought :
Are you sure the area of the edge that you are using to cut the plastic wrap is AS SHARP as the rest of the edge ? Maybe you are feeling / testing sharpness in one area of the edge and cutting plastic with another, duller, part of the edge.
 
I use a boxcutter to cut my shrink-wrap, it cuts better than any knife I currently own and if it ever gets dull I just swap the blade. If you're using a Sebenza for warehouse work, you aren't using the best tool for the job; I used to use all my knives for cutting up cardboard and wrap, until I realized that I hate sharpening and my work-issued boxcutter works best anyways.

Use the tool designed for the work.
 
KingMC said:
I use a boxcutter to cut my shrink-wrap, it cuts better than any knife I currently own and if it ever gets dull I just swap the blade. If you're using a Sebenza for warehouse work, you aren't using the best tool for the job; I used to use all my knives for cutting up cardboard and wrap, until I realized that I hate sharpening and my work-issued boxcutter works best anyways.

Use the tool designed for the work.
Click to expand...

That's cheating.
You cheater, you :)

Sides "real men" sharpen their box knives.
:) :) :) :)
 
Lightening storm getting to be too much going to shut 'er down fo a while
Backsoon
 
To answer a couple of questions in one answer - Yeah - the whole edge is sharp (and did the old Sharpie test to confirm)
I actually got pretty good at sharpening - no wire edges or burrs for me for quite some time now.
One more thing (Kind of a joke), but I once got REEMED here for choosing to use a box cutter on a BOX instead of my sebbie... just saying.. lol
 
jasonbroni said:
To answer a couple of questions in one answer - Yeah - the whole edge is sharp (and did the old Sharpie test to confirm)
I actually got pretty good at sharpening - no wire edges or burrs for me for quite some time now.
One more thing (Kind of a joke), but I once got REEMED here for choosing to use a box cutter on a BOX instead of my sebbie... just saying.. lol
Click to expand...

got REEMED here for choosing to use a box cutter on a BOX instead of my sebbie... just saying.. lol

Yes well they don't know do they !
ALLLLLL the cool guys know you carry a little box cutter to cut boxes / box tape so one doesn't get box tape glue on your real knife. I have had lots of support for that idea / practice.

Ignore 'em.

Just a photo and then back to the problem at hand.
While the storm was going I cut up some little bins to use at work.
I used a SAK that is like pretty much flat ground to the edge. I don't know what the angles are but think well less than 10° per side. These were a little dusty; stored under the crawl space for like ten years. I cut the tops off and trimmed the ends square. The knife hadn't been sharpened in a while (I use it at work to precision cut soft rubber tubing, thick wall ~ 2inch diameter. I keep it mirror and hair whittling when I sharpen it.

I figured after cutting this harder plastic I better check the edge.
It was easily shave sharp.
About three super light strokes on the Spyderco Ultra fine rod and it was back to hair whittling.
The edge did not role or ding at all that I could find. Shaved both directions before I touched it up.
I would think the trimming of the ends would have put some side loading on that thin an edge and rolled it some.

Why, again, do we need edge grinds that are thick behind the edge > 0.20" and angles > 15° ? ? ? ?
I don't. I couldn't even have done the work shown with an edge / knife like that.

I mean this SAK steel is not super. I enjoy super steel for even tougher jobs but edge geometry as stated above.

 
Oh yah . . . back to the prob.
Any chance you have a thickness caliper or micrometer so you can measure the thickness behind the edge ?
Any body know what the norm is ? Hollow ground and all should be pretty thin but maybe this one isn't.

One solution is you could take out your CRK feel how great it is to open.
Put it away.
Take out one of your good cutters and cut the plastic wrap.
That's what I would do but then some people say I enjoy life too much.
 
Box glue knife ?
Here you go . . . even serves double duty as a money clip. You need a money clip right ? Yah me nether but I carry one of these. Can even take the clip off.


The other one I like to recommend is this little guy. The Omega just above the quarter. Too cute to leave behind right ?
 
Grazing the tape may mean you don't apply enough pressure: It could be the handle ergonomics (size, angle, narrowness and slickness) make you feel like you are applying the same, or more, pressure, but in fact you may be quite far off the other two knives in actual delivered force.

I noticed that different handle shapes/textures have a huge, and deceptively discrete, effect in the perception from the hand: A slick handle can seem to require twice the effort: This gets progressively worse with repeated use, to the point you don't know at all the real force you are applying.

Gaston
 
How thick behind the edge can this sebenza be? Why is that a factor? I can cut shrink wrap with kabar that's at 20 degrees and pretty sure it's thicker than sebenza. Your sebbie just got no bite. You just gotta push the knife through then
 
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