Kapara vs. PM2 - Box cutting.

[Zatx]

I purchased a new washer and dryer this week and due to complications with the big-box retailer I had to pick them up and install them myself (first-world problems right?!). Once I had the large boxes off-loaded I set to cutting open the washing machine box with the knife I had in my pocket, my new Kapara. This task was a tremendous effort that required gripping the knife with two hands and using entirely too much force. I checked the box, and there wasn't anything significant about it (single layer, boring cardboard). I checked the blade edge; yep, it was scary sharp. I had several PM2's sitting on my workbench, so I grabbed the Blue version with M390 for the dryer box. With this second knife, the cutting was nearly effortless; it sliced through like a proverbial lightsaber.

Both blades were equally sharp and had identical 17.5-degree edges. So, what do you, the knife experts think caused the disparity in performance with these identical cutting tasks? Was it blade geometry? Handle design? Blade steel? My initial thoughts were that the Kapara should require less effort due to the thinness of the blade material, but that was apparently incorrect.

And let me be clear about something, this isn't me knocking the Kapara, this is a phenomenal knife. I have used it in the kitchen in keeping with the tasks for which Alistair designed it, and it slices like a laser through fruits and vegetables.

[Rutger]

Better handle shape on the PM2.
And maybe it's like with wood that a thicker blade helps push aside the stuff you cut so the edge can keep going. I guess the Kapara is creating too much drag.

[jpm2]

Along with sharpness, edge angle and blade thickness, I find angle of blade in relation to material being cut, push or draw, and transition from secondary to primary grinds make a significant difference in ease of the cut.

[BornIn1500]

My guess is that you used the choil on the PM2, right? Thereby being closer to the blade tip and having much better leverage.

But yea... longer, lighter, thinner blades don't make the best utility knives. No matter how sharp they are. I prefer them to be more stout.

[vivi]

The angle of the cut makes a big difference when it comes to cardboard. Cutting against the grain vs with it, holding the knife perpendicular vs holding it at an angle, etc. That would be my guess.

Were the edges finished at the same grit and edge angle? Those two things make a massive difference as well.

For optimal cardboard slicing, I'd suggest a very thin edge (Anything over 10dps is overkill), 2mm or thinner blade stock, full flat grind, a lower grit finish for edge longevity, cutting with the grain, and holding the knife at a 45 degree angle rather than perpendicular. Box cutters are popular for good reason. :)

I've cut a lot of cardboard if you can't tell :rolleyes:

[Pelagic]

Every cut made on cardboard is different. Sometimes I'll be cutting cardboard like a light sabre, and randomly the apex will catch and want to tear the cardboard rather than cut it. Then the next cut is back to effortless. It must be how it's made, I'm willing to bet (and someone here will already know this) that certain types of cardboard is kind of like particle board, in that all the grains don't run parallel (like with computer paper or lumber). So each time you cut it, it's like a box of chocolates.

[sal]

I agree with Vivi. the angle of attack is critical.

sal

[Evil D]

Making a 90 degree cut straight into a box going against the flutes can be really difficult even with a razor blade. Just turning the blade 45 degrees makes all the difference in the world.

[tps3443]

So 45 degrees helps cutting? I’m gonna try this.

Y’all have me wanting to try some steeep angles. I’m about to see how low my wicked edge can go. Maybe 12dps before the stones rub the clamp.

[Bill1170]

Blade geometry and angle of attack are the biggest factors, in my experience. How thick a knife is behind the edge makes a huge difference. Convexing the transition between edge bevel and primary bevel helps reduce drag in cardboard. This also helps at the top of the bevel on saber ground blades, again to reduce drag.

[p_atrick]

So 45 degrees helps cutting? I’m gonna try this.

Y’all have me wanting to try some steeep angles. I’m about to see how low my wicked edge can go. Maybe 12dps before the stones rub the clamp.

You could always try the Murray Carter method of thinning the entire blade. I personally don't care for the way Taichung does their satin finish, but once you take the blade to the stones, it'll never look like it came from the factory. In fact it make look worse. Sure, the Kapara is made to be used, but it's a pretty knife. It may not be worth it to thin the blade.

[dj moonbat]

The negative blade angle of the PM2 is perfect for the task, even if the blade is thicker than optimal. The Kapara, which is intended to be suitable for kitchen use, is raked slightly back, and doesn't pull cut as effectively.

This is why the world needs a 3mm PM2.

[Evil D]

So 45 degrees helps cutting? I’m gonna try this.

Y’all have me wanting to try some steeep angles. I’m about to see how low my wicked edge can go. Maybe 12dps before the stones rub the clamp.

Anything you cut needs to separate around the blade, and even a 1mm FFG blade is still a wedge shape and will bind up in rigid materials if the material you're cutting is wider/deeper than your blade is tall. So for example it wouldn't be an issue cutting rope but heavy double wall corrugated cut straight at 90 degrees to the board will be very difficult to push the blade through. If you turn the blade at an angle it allows the material to separate around the blade in either direction so the blade doesn't wedge.

[Smaug]

I think what made the difference is that the PM2's blade shape, while probably just as thick at the spine, has a more gentle angle to get to that thickness, whereas the Kapara is more of a "short wedge" shape.

You should Try a Delica or Centofante 3; either will embarass your PM2. This is what we refer to as being "slicey."

The thicker-stocked blade is probably more rugged in really rough treatment or in prying.

[Zatx]

Sorry for not getting back to you guys sooner. Here's an update:

With all things being nearly as equal as could be achieved (sharpened angle, grit size, identical cardboard, and identical operator), I performed an experiment. Angling the Kapara at about 45deg. produced the effortless slicing that I was getting with the PM2 completely perpendicular to the surface.

The good news is, you were all correct!

Thanks!

[Wartstein]

Just wanted to add my experiences concerning cardboard cutting with the Kapara compared to other Knifes: Don´t own a PM 2 at the moment, but compared Kapara to my HAP40 Endura, the Stretch 1 and my Native 5;
Honestly, the Kapara did cut Cardboard the best, no matter what angle. Not by far, but noticable. So I am still puzzled by the OP´s findings, cause I can´t imagine the PM 2 beeing a far better slicer than the Endura,Stretch or Native 5 - ?

[Zatx]

Just wanted to add my experiences concerning cardboard cutting with the Kapara compared to other Knifes: Don´t own a PM 2 at the moment, but compared Kapara to my HAP40 Endura, the Stretch 1 and my Native 5;
Honestly, the Kapara did cut Cardboard the best, no matter what angle. Not by far, but noticable. So I am still puzzled by the OP´s findings, cause I can´t imagine the PM 2 beeing a far better slicer than the Endura,Stretch or Native 5 - ?

You would do your burgeoning collection well by adding a PM2. Actually, come to think of it, they may not like you getting a PM2 since it will probably end up getting more special time with you.

[Wartstein]

Just wanted to add my experiences concerning cardboard cutting with the Kapara compared to other Knifes: Don´t own a PM 2 at the moment, but compared Kapara to my HAP40 Endura, the Stretch 1 and my Native 5;
Honestly, the Kapara did cut Cardboard the best, no matter what angle. Not by far, but noticable. So I am still puzzled by the OP´s findings, cause I can´t imagine the PM 2 beeing a far better slicer than the Endura,Stretch or Native 5 - ?

You would do your burgeoning collection well by adding a PM2. Actually, come to think of it, they may not like you getting a PM2 since it will probably end up getting more special time with you.

Oh yes, sure I´d like to own and try out a PM2! But,you know, I am not exactly the most wealthy guy on earth and my other hobbies require some money too.. like for ropes, skis, trail-running shoes..
So in the beginning I tried to convince myself that my goal concerning Knifes was to own only ONE for everything eventually... and that I´d have to try several to find that one.. ; than it was ONE large and ONE small... and so on
Right now I try NOT to get more knifes than I own currently or always sell one to purchase another - does work sometimes, but not everytime..
Bad thing is: Here in Europe you have to pay way more for Spyderco knifes than in the US: The Kapara I got for about 220 Euros (which is arould 250 USD), and that was the cheapest offer I could find...
/ But back to the original topic: As you own a PM2: Do you think it is a better cardboard-cutter than the Endura or Stretch? Or did you even try that out maybe? Just curious...

[Smaug]

PM2 has a wider blade, thus it's a narrower angle wedge and cuts easier.

Wait til you try a Centofante 3 or Spydiechef. Good ol' Delica is no slouch either.

[Jazz]

I cut tons of cardboard. Like they said, angle the cut and it flies through. 90° is generally way harder. Weird.

You can’t go wrong with a Delica wharncliffe, by the way. It was literally made for it.