Dive Knife Material vs. Corrosion: Titanium, H1, LC200N

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doctormike

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I've already read of people using a dive knife as a pry bar; don't recall why. I think many people are accustomed to using knives for various things, and that familiarity colors their choice of dive gear.

I mean, I guess that a knife would be better for prying open shellfish. But seriously, the main safety reason why every diver is supposed to carry two cutting devices is because of entanglement. Sure, there are certain very specific situations where a knife may be better (stabbing fish is the only one I can think of offhand), but we don't recommend that every diver carry one of these in case they need to grab a porthole...

Jersey_Deco_Bottle.JPG



Thanks for reporting the good experience. Years ago I bought a Black Friday special 'titanium coated' cheap dive knife, and it rusted up quite readily. Your link says heavy-duty stainless steel blades with titanium nitride coating to resist corrosion. Cheap enough to replace if they ever get dull. Also glad you mentioned the joint held up.

Yeah, I mean they eventually get some discoloration on them if you dive enough, but unlike a knife (where you are depending on the blade being very sharp), a shears works by leverage and pressure. So unless it was REALLY dull, it's probably going to work fine. And if you are compulsive about your gear, just throw in another $8 each season so you always have a new one. It's a sport where we spend $1400 on a flashlight! :)


To me, a major selling point for H1 and LC200N knives is that they are not a lot of work and worry to keep in decent shape (I'm about function more than form; a slight orange glaze patch I can live with). A standard stainless steel dive knife, on the other hand, can be exactly what you describe - after the dive, quickly get a fresh water rinse and dry it. Too much hassle.

One question that comes up...is your cutting tool solely for diving, or do you carry it in other activities (e.g.: as a general purpose pocket knife)? I used mine this morning to pop the balloons cluttering our floor to throw away while our kid's at school.

It's a general purpose cutting tool, which is very handy for diving, topside and underwater. And since it's on my webbing, I always have it with me. I used it recently to free an entangled diver, and I will cut abandoned monofilament on a wreck to keep others from getting tangled, but I also use it for trimming cave line, zip ties, etc... I keep on in the kitchen drawer for household stuff. Unless you need to cut a clean line on paper (for a kids art project or something), they work better than any other scissors...
 

Jcp2

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Or if you are left handed. I finally got a pair of left handed trauma shears for my left handed daughter, just in time for her develop other teen girl non diving interests. I tried them myself and no es bueno for my right hand.
 

doctormike

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Or if you are left handed. I finally got a pair of left handed trauma shears for my left handed daughter, just in time for her develop other teen girl non diving interests. I tried them myself and no es bueno for my right hand.

Googling "left handed trauma shears" certainly shows plenty of them. So if you are a left handed diver, left handed trauma shears would be the way to go!
 

plaamook

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Few thoughts...in no particular order.

-I wouldn't want to try getting through thick rope fast w shears and 5mm mitts on. One of the few people I know who died in the underworld got tangled by a boat that was dragging its rigging. Def want a fast one handed solution in such a situation.
-Used to dive scallops commercially. You don't want to a really sharp thick knife to open them. You want a straight edge thin bendy kitchen knife with the tip rounded clean off so you don't stick it in your hand.
-A few of the commercial divers I've worked/dived with prefer Mora Swedish cheapo hunting knives. Yeah, they rust right up but you can still get a great edge on them, ignore the rust, and when you need a tool to cut pry bang what have you, you just grab it and use it rather than worry about damaging your very expensive fancy pants knife. If it breaks or swims off you just grab another. They bought em by the pack so they were always around, taped to umbilicals etc. I like that reasoning a lot actually but I like my Atlantic/Pacific salts too.
-Some years back I used to carry an old Spyderco Delica diving every day working on live-aboards and dive boats. It held and edge well, cut everything like butter, and to keep the rust back I'd hit it w WD40 every few days. As soo as you cut anything and the layer of WD40 has been worn off it would rust right up. So I'd clean it and spay it and get back in the drink. Not really a big deal. Made it through an entire dive season in SE Asia w no problems, then it got replaced by an Atlantic Salt.

I think that's all I've got. Cheers
 

Ukmc

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I guess my question would be that unless you are spearing and need to kill fish, why would you not just use trauma shears?

For the actual intended purpose of cutting yourself free from intanglement, shears are vastly more efficient and safer than any knife. Titanium shears are $8.00, I have had my current set on my rig for a few years. I guess they are a bit tarnished, but if they ever stopped working I would just replace them. I have never seen the joint break, and they will cut through just about anything without the risk of cutting yourself. The one time I tried to use a dive knife to do something scuba related in Cozumel, it ended up with me searching for a tetanus booster at a local pharmacy...

Am I missing something? Why it has to be a knife at depth? This seems to be a LOT of work, cost and worry to keep the knife in good shape - something that I never consider with trauma shears. I do carry a trilobite as a backup (another safe and convenient option, but not as multi-purpose as shears).

Sorry, I know that wasn't really what the point of this thread was, but I'm always willing to learn!
Hi @doctormike . Where do you keep you trauma shears on your harness to keep them out of the way until you need them?
 

vjb.knife1

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I work as a Professional Diver and Engineer on a Submarine and two surface boats, so I use knives in and around Seawater almost every day.
I have 3 Spyderco knives made of H1, and 1 made of LC200N. I also have a couple of Mission Knives that are Beta Titanium and finally a UDT knife made from Haynes Alloy No. 25 (primarily Cobalt, Chromium, Tungsten and Nickel).
I recently bought the Spyderco Caribbean (lower left) with the LC200N Blade and really have not used enough to make any comparisons.
I have had Mission knives for many years but have only used them marginally but in my experience they are pretty tough and do cut through monofilliment and rope pretty well and hold an edge fairly well. They also have absolutely no corrossion.
The two knives I use the most in the past 5 years are the Spyderco Pacific Salt (H1) (center) and the Autonomy (H1). I use the Pacific at work mainly on the surface but it get salt water on it all the time. This knife is not serrated. It has the most use of probably any knife that I own. I cut Monofiliment, rope (nylon, Polypropylene and hemp), nets, boxes, tape, wire, gaskets, rubber, etc. The H1 Autonomy (lower center , orange) is fully serrated and goes on recreational dives and cuts a little bit of stuff. The plain blade cuts better with less effort and holds up better than the serrated; it is also easier to resharpen than the serrations. I have had very little corrosion on the H1 blades. They do require resharpening more often than steel knives but when I get the edge at about 17 degrees per side, on the non serrated blade, it does pretty well.
The UDT knife (Top) is something that none of you would likely be able to find or willing to buy (only 1200 were made in the 1960's), but it will cut rope and steel and anyting else in between. I use it rarely on recreational dives.
knives.jpg
 

vjb.knife1

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I am a professional diver and I always dive with a relatively large knife. I understand the people who are sport divers and don't want to carry one for whatever reason, but don't try to tell me that there is no reason to have one, because with well over 18,000 hours diving in 52 years of diving commercially, recreationally and professionally I know better. If you need to cut through 1" blue steel marine rope and remove a net made of it wrapped up in the the props of a submarine or surface boat using trauma shears and a trilobite, good luck. I will see you in a week or so. There are reasons for knives of that size and cutting ability, as well as just "old habits die hard". Besides who knows when you will need to cut some bad guy's air hose, shears are too slow and a trilobite just won't do at all.
 

doctormike

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I am a professional diver and I always dive with a relatively large knife. I understand the people who are sport divers and don't want to carry one for whatever reason, but don't try to tell me that there is no reason to have one, because with well over 18,000 hours diving in 52 years of diving commercially, recreationally and professionally I know better. If you need to cut through 1" blue steel marine rope and remove a net made of it wrapped up in the the props of a submarine or surface boat using trauma shears and a trilobite, good luck. I will see you in a week or so. There are reasons for knives of that size and cutting ability, as well as just "old habits die hard". Besides who knows when you will need to cut some bad guy's air hose, shears are too slow and a trilobite just won't do at all.

I'm actually interested in this point, and I certainly respect your experience, but maybe consider how much of this statement really is "old habits die hard".

First of all, I don't think that it's controversial to say that you should have a cutting device. And obviously you can't cut 1" rope with a trilobite, I don't think that it's a substitute. But it's also not why every open water diver needs at least one cutting device.

Do you really think that it's easier to cut heavy rope with a knife than a shears? The issues is simply blade pressure. You can exert far greater pressure on whatever you are cutting with shears than with a knife, which is why you could cut steel cable with shears. I can't imagine the amount of sawing and force you would need to apply with a knife to get through something that heavy, and ther is also the safety issue of exerting that much externally directed force on a sharp blade under water.

And as was mentioned in another thread, clearing a fouled prop isn't the reason why people say that every diver in open water should carry a cutting device. That's not entanglement, in the sense of a potentially lethal diving accident. It's an underwater task, and maybe a knife is good for that. Hey, there are a lot of underwater tasks that are best done with specific tools, which is why divers sometimes carry sledgehammers, pry bars, bolt cutters or even dredges. But no one says that all divers should carry those things, just because they are better than a knife or shears for some types of work.

I think I could cut through a bad guys air hose pretty quickly with shears!
 
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