Cutting tool comparison test

[Malpaso]

Based on Akimbo's recommendation of the Z knife, and my experience with the Benchmade cutters in the EMS world, I did a comparison test of the two.

This comparison was done in a controlled environment, not in the field, so take that into consideration when interpreting the results. I also have no dive experience as I'm am only now taking my dive classes. I tried to replicate what I thought might be dive conditions.

The cutters I compared were the Benchmade 8 BLKADC and the Carbon Black Captain Knife by hookknife.com (non-functioning web site) from Sweden. I found both of them available on the parachuting web site paragear.com (I have no affiliation). Cost: Benchmade $30, Z knife $13.
Testing was done on a variety of materials in different configurations: paracord, standard rope, nylon rope, 1” webbing, tie wraps and BDUs. I used single strands and braids of 3 on the paracord and rope, and multiple thicknesses of the BDUs. I tested the cutting in air and under water.
These are the two cutters and sheaths. The first major difference is the Benchmade comes with a hard sheath and Malice clip. The Z knife has a rather flimsy nylon sheath. Additionally, the Benchmade cutter is metal, the Z knife has a plastic handle.

Next, the finger holes in the Z knife are much smaller than the Benchmade. I have small hands and can barely get a gloved finger in the Z knife hole. In contrast, when not using the finger hole, the Z knife is actually more ergonomically comfortable.

The first cutting tests were done on single strands of paracord shoelaces (EMS environment), regular rope and nylon rope.

The Z knife cut all three much easier than the Benchmade, but the design thickness of the Z knife made it hard to hook the shoelace in the boot. In open air it cut as easily as the ropes. First test advantage Z knife.
Next test was 3 strands of braided paracord, regular rope and nylon rope.

While the Z knife easily cut the braided paracord, it had a hard time with the thickness of the braided ropes into the narrow slot of the cutting space. It barely fit the nylon braid, and could not fit the regular rope braid. Advantage Benchmade.
Next was the BDUs.

This was the first real noticeable difference between the two cutters. While the Z knife cut just as easily, and possibly more easily than the Benchmade on the initial cuts of single thicknesses, it immediately began to clog with threads. Upon doubling the thickness of the cloth, the Z knife clogged drastically, and had to be taken apart. At this point, there were visible signs of damage to the Z knife blades. Advantage Benchmade.

I next tested the paracord and ropes underwater (soaked and waterlogged after sitting in the water for a period of time). The results were virtually the same as dry testing of single and braided strands. Advantage Z knife.
I tested the tie wrap (similar to six pack rings in consistency), and while the Z knife cut somewhat more easily than the Benchmade, there was more visible damage to the blades. Push.

The final test was the 1” webbing.

The initial cuts were equivalent, but the Z knife clogged again, and showed more signs of blade damage. Advantage Benchmade.

At this point I did multiple random cuts with both cutters on paracord, rope and BDU cloth. The Z knife continued to function as well or better on the single strands of paracord and rope, but again clogged on the BDU. I completely broke it down and cleaned it again. The blade damage was increased, and more noticeable. In addition, the screw heads showed signs of wear and looked as though they might strip with much more use. Advantage Benchmade.

In contrast, the Benchmade looks like it did out of the box.

In conclusion, the Z knife is a very good tool, but has its limitations under certain conditions with certain materials. Specifically, thick and/or threaded materials will cause it to fail. In addition, the life expectancy is questionable. While replacement blades are available ($4/set), the constant opening and closing of the plastic frame and weak screw heads leaves that option in question. It won many battles, but lost the war. The Benchmade needs somewhat more effort to cut smaller/thinner materials due to the curved cutting surface, but excels on the thicker ones. In medical environments, the Benchmade wins hands down. In the dive world, I’d guess that the Z knife would have the edge on fishing line, light netting and the like, but probably only in its early life. Two is one and one is none, so carrying both is an option. Personally, I’d also go with a pair of trauma shears as backup to either.

 

[buddhasummer]

Thank you for taking the time and effort to write such a detailed review. Good luck with your diving classes.

 

[Akimbo]

Malpaso, thanks for your good work. I was surprised at the clogging because it has never happened to me. For those who have not read the previous posts, here they are:

http://www.scubaboard.com/forums/kn...ave-any-experience-line-cutter-benchmade.html

http://www.scubaboard.com/forums/knives-cutting-tools/315577-great-z-knife.html

I took my Z-knife with blades about a year old and tried some experiments. Since my main use of the Z-knife is clearing entanglements, I started on ¼" double-braided Nylon. I have never had any difficulty simply unhooking an entanglement on larger lines. After cutting 40 pieces off about ¾” long I was getting bewildered since a saw no sign of clogging. I then started pulling hard to one side rather than trying to keep cuts square as is my habit. Still no clogging. Then I tried left handed pulling hard to one side. That is when I began to notice buildup. Unfortunately, this was not conclusive since the blades were surely getting dull by then.

I switched to ¼" Polypropylene line and gave up after 40 cuts concluding that the large monofilament fibers are unlikely to clog even with very dull blades, which they were by then. Then I switched to 2" Nylon weight belt webbing. It still cut, but very poorly due to the dull blades.

I switched blades and continued the webbing test. Still no clogging. This is probably due to the resins that minimize fraying compared to the 1" webbing in your test. Next I switched to some 1050 Denier/16 Oz/yard² Ballistic Nylon scraps. After six cuts about 6" long I began to notice some fiber buildup. I cleaned the blades without disassembly and repeated the test in a deep sink just to see if the water would have any effect by washing away the fibers. I got another 22 strips before noticing fiber buildup. At that point, It occurred to me that cutting sheet fabric was of little interest to a diver, unlike a paramedic, and switched back to the ¼" double-braid. I started to notice significantly increased resistance but no clogging. At this point, I went back to the Ballistic Nylon just to see what happened and it clogged badly on the first stoke.

I am not sure if my conclusions are correct, but here is what I think is going on. A Z-knife performs best cutting fibers that are near perpendicular to the cutting edge. As the blades dull, the force is increased and the two single bevel blades are forced apart resulting in clogging. I think this is consistent with the assumption in the previous thread:

… The double/opposing blades make it nearly impossible; unless you let the blades get really dull.

A negative characteristic of Z-knives is the part of the blade closest to the bottom of the “V” does the most cutting, and therefore dulls the fastest. The rest of the blade can still be like new. Unfortunately the replaceable blades in the Z-knife I like can’t be flipped 180°....

It always comes down to tradeoffs, especially with cutting edges. Unfortunately, the materials capable of obtaining the keenest edges don’t have nearly enough corrosion resistance for salt water. The materials being cut also make a huge difference.

When it comes to non-disposable cutting edges, you also have to consider your ability to sharpen the edge. I think it is fair to say that hook knives are one of the more difficult edges to sharpen. It isn’t difficult to learn but requires some effort and unusual hones.

I did try the OMS Titanium Hook cutter and couldn’t get a decent edge on it. I worked the blade with conical diamond hones and checked it under 60 power microscope to make sure I didn’t roll the edge. I have little experience with sharpening Titanium, but I suspect the alloy or heat treating is not ideal for a cutting edge. I have no doubt that the Benchmade blades do not share this deficiency. The sheath is decent though.



I agree with most of your conclusions but am not sure all of them are applicable to divers. There is enough information here that divers can make their own judgment. It certainly made me more aware of the strengths and weaknesses.

For divers trying to make a choice it is important to point out that heavily incrusted line, like fishing net that has been underwater for years, will dull any cutting edge quickly due to the abrasive nature of calcified marine organisms and silt. Also, hook and Z-knives are both very poor choices for clearing boat props so better tools should be onboard.

 

[Akimbo]

This post got me thinking about knives. There is a school of thought that diving knives should be cheap and expendable since they are so easily lost — the modified dollar-store steak knife being the poster boy. There isn’t much that people put in the ocean that doesn’t get lost, broken, and/or corroded so the concept is justifiable.

The “lost part” is a little more difficult for me to accept since the likelihood is you will drop it when you need it most. That is one reason I have become a fan of Tee or Push handle fixed blade knives. It is easy to hold between your middle fingers and still have nearly full use of your hand even when holding an anchor line, changing regulators, or untangling line.

There are advantages to a Z or Hook knife, especially for cutting monofilament and small line. That brought me into the shop resulting in the experiment shown by the attached photos. I found that the Tee doesn’t have to be very wide since the force applied to this type of knife is low. The downside it the geometry for storage is more challenging.

I am not suggesting that everyone go out and make this modification, but there may be a product ideal buried here somewhere. Here are some characteristics of what I think would make a great backup knife to clear entanglements.

• The cost needs to be low so a glass or carbon filled injection molded body is probably in order.
• I still favor opposing single bevel disposable blades since few divers have the skill or patience to sharpen them. Besides, they cut amazingly well when sharp
• Those blades should be reversible though since the point at the base of the “V” dulls long before the rest of the blade.
• They should be a little longer than this Z-knife, but not more than a ¼" opening so hoses and fingers are safe from accidental cuts.
• The handle should be designed so it can be held like a push knife — thin cross section between the middle fingers and short horns forming the Tee.
• The two halves of the handle should be held together with stainless screws with nuts to avoid the stripping problem of this Z-knife.
• A sheath should be provided that can go on 2" webbing or be strapped to an arm with a wrist strap.

Any other ideas?

 

[Shftrdog]

Good luck with your dive classes, you will love it. The adventure begins.

 

[VooDooGasMan]

Here is my favorite knife, tucks away anywhere.

 

[VooDooGasMan]

Oh and akimbo I clip on d ring on harness or weightbelt, and it has a belt clip in Pic 2, no sheath needed.

 

[Malpaso]

This post got me thinking about knives. There is a school of thought that diving knives should be cheap and expendable since they are so easily lost

Does an arms-length keeper from the cutter to a carabiner on your vest make sense, or would that just get in the way?

 

[Akimbo]

VooDooGasMan: We use cheap folding knives a lot commercial diving for backup — by backup I mean to take over for a dull knife. The disadvantage as a Scuba diver’s entanglement knife is it takes time and two hands to open.

The Queen Big Chief #45 Folding Knife holds a really decent edge and is about a cheap as you can get. You have to grind a big half-moon into the aluminum body to make it easy to open with gloves and cold hands. In moderate temperature water they slip up your wetsuit sleeve and you don’t even need a snap. I still have 5-6 but don’t carry on recreational Scuba dives much unless I plan to cut a lot of encrusted line.

Queen Cutlery Co Knives queen cutlery big chief regular fol - TheGunSource

 

[BKP]

One word: Trilobite

EEZYCUT FULL DEMO - YouTube

It works *exactly* as in the vid... I have three of 'em