Dive Knives 101: Features And Maintenance

Material

The performance and longevity of your knife will depend on the type of material used to forge the blade. The two materials most commonly used to make diving knives are titanium and steel.

Titanium knives are very strong and lightweight. They weigh almost twice as little as similar size steel dive knives. Titanium alloy is also resistant to corrosion, which means that knives made from this materials are basically maintenance free. On the downside, titanium knives can be hard to sharpen, and they come with a higher price tag.

Stainless steel dive knives are easy to sharpen, but they require more maintenance to prevent them from rusting. If you get a steel knife, you will have to wash it with fresh water after each dive and let it dry before putting it in its sheath.

Steel knives usually come in two different alloys - 300 and 400. The 300 alloy has higher corrosion resistance, but needs more sharpening, whereas the 400 alloy holds its edge better, but is more prone to rusting.

Type of Blade

A dive knife can have either a fixed blade or a folding blade.

Knives with a fixed blade are generally considered to be more reliable. You can easily take this type of knife out and use it with one hand. Most dive knives with a fixed blade also come with a sheath for safe storage.

Knives with a foldable blade have the added convenience of taking up less space and being safer to carry. However, these models can be hard to open with one hand.

Edge of the Blade

The edge of the blade can be straight or serrated.

A straight blade is better for slicing things and cutting plastics or nylon rope.

A serrated blade, on the other hand, is good for sawing through natural fibers or kelp.

The best option would be to look for a knife that has both a straight and a serrated edge, as well as a notch in the blade for cutting fishing line.

Tip of the Blade

The tip of the blade can be blunt, sharp or tanto.

A blunt tip is great if you don’t plan to use your knife for stabbing and piercing. It makes the knife safer and prevents you from accidentally puncturing the hoses, exposure suits or BCDs. In addition to that, blunt tip knives can be used for digging, hacking, and chiseling.

A sharp tip is most popular among those divers, who are into spearfishing. It is better for finer cuts and makes it easy to spike the fish. However, a sharp tip knife is more likely to cause accidents, so you should always carry it in a sheath.

A tanto tip is a hybrid of a blunt and a sharp tip. It has a high point with a flat grind. This particular design structure makes for an extremely strong point, capable of puncturing even very hard materials. However, because the front edge of the tanto knife meets the back (unsharpened) edge at an angle, rather than a curve, this type of knife has no belly and is not the best choice if are looking for a general utility tool.

Size

Bigger is not always better. In fact, when it comes to dive knives a more compact tool is often the preferred option. A large, bulky knife is usually not necessary for recreational divers. What’s more, if you carry it on your calf, it can present an entanglement risk of its own. Instead, a dive knife with a 3-4 inch (7-10 cm) blade will be enough to cut through the net, and it will fit easily in your BC pocket.

A bigger knife can be a good idea if you plan to use it for spearfishing or want to go kelp diving.

Whichever size choose, make sure that you can reach the knife easily and have a firm grasp on the handle even when wearing thicker gloves, a big dive computer or other bulky piece of equipment.

Dive Knife Maintenance Tips

Before the dive inspect the knife for corrosion. In case you discover that your dive knife has some rust spots, you can use a cleaning solution and wipe the blade with a clean cloth, a towel or some soft steel wool.
After that, you should check whether the locking mechanism on your knife and/or sheath works properly. If needed, lubricate it with silicone.
If you can, disassemble your knife every once in a while. Remove a handle and give the tool a really thorough clean to make sure no salt or sand has found its way into the inner parts of the knife.
Sharpen your dive knife if necessary. To sharpen a plain edge simply use a cross-hatched fine metal file. This way the edge will be sharp but rough. It will slice through the rope better than the stone-sharpened edge. If you need to sharpen a serrated blade, bear in mind, it is more difficult to restore without changing its shape. The process is also quite time-consuming, so it is best to sharpen your serrated knives only when you notice them becoming less effective. The most common way to sharpen serrated blade knives is with a sharpening rod. All you need to do is determine the side of your knife with a beveled edge and run the rod along each of the serrated scallops at an angle of the bevel (typically 13-17 degrees).
After each dive rinse your knife with fresh water and scrub it to remove any leftover salt or debris. Dry the knife thoroughly.
After you’re done diving for the day, you can coat the blade with silicone grease.

Finally remember, whichever knife you choose, you should never use it to harass marine life or destroy habitats. A dive knife is primarily a safety tool, not a weapon, so use it safely and responsibly.