The life-cycle of a diving knife

[icechip]

Medium size. Strapped to leg. Blunt tip. Use it to pry something or cut line/rope from a prop or whatever. It's a tool. Use it. Don't cry if you lose it. Line cutter in sheath on harness belt.

 

[JamesBon92007]

As a 'knife enthusiast' I've noticed that typically the dive knife is a relatively inexpensive item (compared to other knives).

This appears to be largely due to the diving knife being almost a consumable. It seems many are simply lost, or suffer from corrosion.

I also suspect, unlike other knives, diving knives are rarely collected or displayed, and when bought will be used. A simple, utilitarian, tool.

So in this price range where you are not too fussed if you lose the knife, you may not be too bothered about maintenance as when it corrodes or blunts, you might just buy a new one.

I'm wondering what the general attitude is towards the dive knife and if the typical diver will ever sharpen theirs and how long these blades generally live before being replaced?

What is the life-cycle of your dive knife? Do you care for it? Do you sharpen it?

I bought my knife from Aqua-Craft via mail order in 1969. I have replaced the sheath straps a few times and the rubber, round tab holder has been modified to accommodate what's currently available. I sharpen the regular edge before a dive but have sharpened the serrated edge only a few times as it requires some planning. The Aqua-Craft "Panic Button" is still on the sheath after all of these years! So far I have not killed any sharks or alligators with it nor have I ever cut the exhaust hose of a double-hose regulator. I have cleaned quite a few fish with it though.

Since I don't like to do checked bags I don't take it with me on dive trips but considering that in 47 years I have never actually needed it I am not too worried.

 

[Shotmaster]

Here's my dive knife and I have a Scubapro one hiding from me in storage. Here is my Model 14 Randal for size comparison. The floor tile is 18". I have no use for toy knives. During my military service, most of the guys had cool looking double edged killer knives and liked to make fun of my "crew served size knife", which looked even bigger since I am only 5'6", but every time we were in the field they always wanted to borrow it.

 

[Rhone Man]

I use a broken off and filed down steak knife, kept in my belt webbing. If I lose it, it is 2 bucks to replace. I lose about one ever 5 years or so.

 

[Eric Sedletzky]

The best cutting knife I have ever found is a Swiss serrated cheap throw-away with a plastic handle. The blade is short and blunt but it's really sharp and cuts through anything. I learned about them when I got a call to unfoul a prop on a crab boat that caught up a bunch of it's own crab pot line. I showed up with my usual cutting tools and the crab fisherman handed me one of his cheapo line knives to try and it worked better than anything I'd ever used. They're only $10 each and they buy them by the case.
I made a sheath out of some weight belt webbing and some aluminum rivets and now it permanently lives on my harness waist belt.
I also use a Riffe freedive hunting knife for dipatching fish. It's about a 5" blade sharp point dagger style and it's designed to spike the spinal cord of fish to put them out after spearing them. I use it for both freediving and scuba whenever I'm hunting. Nothing worse than a pissed off lingcod on your stringer pulling you around.
I also have a mid 60's Aqualung Seahawk which is a classically huge knife. Some would say this knife is what originally defined the BFK.
I keep it strapped to the inside of my calf and only use it to harvest rock scallops since the blade is almost 8" long. The regulations for taking rock scallops specifies that only dive knives or legal abalone irons are allowed to pry scallops so the the dive knife is much more convenient for me to use and stow. This isn't a knife I would take anywhere except for a scallop dive in my local waters.

 

[tbone1004]

no good knives used in scuba, risk of getting lost and abused is too high. I know for a fact that they will be used for things I would never allow my good knives to be used for. Benchmade 7 Z-knife is my preferred, the trilobites are great as well. Cheap trauma shears come with me. VERY rare that that isn't enough for normal diving. If I was spear fishing, I would carry a normal dive knife, but it's a tool, nothing more.
Deep-Outdoors-Quickdraw-Point-Blade-Knife
would probably grab something like that for spear fishing.

 

[Shotmaster]

I have a small flat point sheath knife with a serrated edge on my BC along with some medical shears, which from a practical standpoint are sufficient for 99% of cutting duties. I spearfish, so I am used to having my large dive knife on my leg. I call it insurance. I got entangled once in some old fishing net on a wreck while chasing fish. It was the one and only time I really needed my big knife.

 

[DevonDiver]

Quite simply..... carry the right tool for the job. I don't really agree with some of the views that a dive knife should be 'jack of all trades' to cover every eventuality and purpose.

For most divers, a simple Trilobite is a cheaper, safe and very effective. It'll cut easily through lines (including loose monofilament), webbing or neoprene.... has uses to escape entanglement or in rescue scenarios. I've even cut though regulator hoses with a trilobite (as a demonstration/for a bet) - but they're not prone to accidentally cutting something, or yourself.

If electrical wiring (i,e, in some wrecks) or steel trace fishing lines were an anticipated hazard, I'd add a substantial pair of cutters/shears to my kit. Trilobites won't sever metal lines/wire.

I very rarely carry a bladed knife nowadays. I have a couple of Halcyon Ti knives at the bottom of a drawer. I used to carry them religiously, until I switched to using the Trilobites years ago. I've never missed them.

Trilobites aren't stainless, so they rust quickly. However, they do maintain a sharp blade, as it's essentially a razor. For maintenance, I soak in fresh water and give a spurt of WD40 occasionally. Each cutter comes with spare blades. I find that Trilobites, including using the spare blades, last around 2-3 years if maintained.... and that's diving very frequently. They're very cheap to replace.

For prying or hammering.... I'd carry a specific tool. There's some nifty tools on the market great for these purposes. They're task specific, based on a defined need in the dive mission.

I don't spearfish or hunt. If I did.... I'd probably carry a dedicated fisherman's blade.... that'd have a purpose both on, and under, water.

Unless you have specific need for a sharp pointed knife, get a blunt tip. Pointed knives risk injury to self or damage to equipment. A punctured BCD or drysuit is a very real hazard.... and generally outweighs whatever need you'd have for a puncturing/stabbing tip blade.

Back when I was a relative novice diver, I carried a SOG Seal Pup blade. Great knife... sharp as a razor.... but it was complete overkill for the purposes needed.... and eventually it went on eBay. I only had it because of my military service.... one of two blades... the other being a Fairburn-Sykes dagger.... which would have been hilariously 'Walter Mitty' strapped on as a dive knife! LOL

 

[TacticalReviews]

Thanks for all the great answers so far

He calmed down long enough to ask me for my knife because he wanted to cut some line to tie to me and a buoy so that he could find us after the second dive. He cut the line with my knife and almost had a stroke because my knife was so sharp. He spent a few minutes bashing my knife against the cutting board while screaming at me that you should never, ever take a sharp knife under water with you because you can cut yourself easily and not feel it until you bled out. He might have said more but who listens to someone who is screaming at you and destroying your prized possessions?

I have never been able to get a good edge on that knife.

@Pedro Burrito ,excellent story and a good reason to have a blunt tip if the edge is sharp.

I have a small flat point sheath knife with a serrated edge on my BC along with some medical shears, which from a practical standpoint are sufficient for 99% of cutting duties. I spearfish, so I am used to having my large dive knife on my leg. I call it insurance. I got entangled once in some old fishing net on a wreck while chasing fish. It was the one and only time I really needed my big knife.

I think @Shotmaster 's reply sums up one of the biggest reasons to carry a more substantial tool. Yes a line cutter and shears will cover 99% of normal cutting tasks, but I'd far rather carry a knife and not need it than need it and not have one when faced with a much more serious situation. How many people pay for insurance they never use?

Also in this same reply is the main reason to carry a decent knife, and that is hunting/harvesting fruits of the sea.


All these insights are great, but this thread was intended to look at the lifespan, maintenance (cleaning and sharpening) and cost of dive knives. Any more insight into this aspect?

 

[Storker]

this thread was intended to look at the lifespan, maintenance (cleaning and sharpening) and cost of dive knives

My opinion:

Lifespan: Until I lose it.
Cleaning: Even stainless rusts in seawater after a while. Rinse after each dive/dive day let dry, coat with a light sheen of silicone grease.
Sharpening: Keep it as sharp as the steel allows, but don't sweat it. As I've said, the type of stainless steel used in the typical dive knife doesn't hold an edge well. Titanium is even worse.
Cost: As cheap as possible while still having the properties you want of the knife.

And finally: I harbor a deep distrust to pushbutton-type locking mechanisms on the sheath. I want either a rubber strap that goes over the handle, or a locking system that can't be accidentally opened by just bumping it against something, like a squeeze lock.