Best knive metal?

[MikeS]

What is the best material for a knife?

Titanium is expensive and doesn't hold an edge well?

300 series stainless steel is more corrosion resistant but doesn't hold an edge.

400 series stainless steal holds an edge better but is less corrosion resistant.

 

[MNScuba]

That's why it's best to find one in between so you get the best of both worlds. The Scubapro K-3 is one such knife, I'm sure there are many others, but that's one off the top of my head.

 

[VTWarrenG]

Mike,

The best knife, IMO, is a combo of a 300 stainless blade and a ceramic line cutter. A 300 stainless blade holds up the best, and holds an edge good enough to cut about anything you'll ever come across underwater. Ceramic line cutters can be purchased in a curved piece of plastic that allows you to just swipe at line to cut it. Some knives also come with the ceramic blades on them. The ceramic is extremely sharp and corrosion-proof, but brittle.

- Warren

 

[devjr]

That one has been beat around a bit. Outside of an expensive, military knife by Phoenix(Spain), I don't know of one that avoids all of the issues above. I never heard of a K3 knife and I don't know what the Minnesota link is all about. I would like to hear more though.

I often wondered why they don't make a knife from the same steel used in speargun arrows, 17-4 PH. That stuff is really tough.

 

[MNScuba]

Originally posted by devjr
I never heard of a K3 knife and I don't know what the Minnesota link is all about. I would like to hear more though.

The knife:
http://www.scubapro.com/consumer/products/accessories/knives/k3.jpg

The Minnesota Link:
That's just part of my signature, sorry if it confused you...

 

[jbd]

Just my thoughts for MikeS--From what you have posted about about the metal above I would go with the 300 series stainless.

My reasoning is this. The 300 gives you the corosion resistance which will help the knife last a long time. Granted it may not hold an edge as well as the 400 series but keep in mind that sharpening or maintaining a fine edge will be easier to do with the 300 than with the 400.

Get the edge on the 300 and then learn to use a butchers steel. After any dive that you use the knife use the steel. This makes the assumption that you are using the knife to cut biologogical materials and not using the knife to kill a snake in a rock pile. In the snake killing case then you will need to find someone with a knife grinder to recondition the blade. I have one of those grinders. It makes really short work of highly damaged edges.

 

[DrySuitDave]

17-4 stainless steel has a chromium content of 17% (versus 18% for 300 series stainless steel) and a nickel content of 4% (versus 8%) to assure a properly hardened material. This further explains the material being designated as 17-4 ph stainless steel (17% chromium and 4% nickel). The "ph" which follows the 17-4 designation designates the materials "precipitate hardness."

The corrosion resistance of 17-4 ph versus 300 series stainless is reduced less than 5%.

 

[FredT]

My personal opinion is that a knife has to conform to several requirements to be useful for diving, although the requirements can vary with location and diving activity.

1. As a rule the knife should be large enough to do the WORST job it could be asked to do in your area. A 2" blade while spearfishing for 6' long fish in an area of entanglements is a bit of an understatement, although a 10" blade whle spearfishing for "plate sized" fish can be much of an overstatement unless there is a significant entanglement hazard. It is usually possible to do a job with a large knife that could be done with a smaller one, but the reverse is not always true.

2. A dull knife is a really bad club, and not much use except as a pry bar. As a cutting implement you'd be better off using barnacles than a dull blade.

3. 300 series SST is pretty much the bubble gum of steels. Corrosion of the edge will dull the blade over a couple days diving EVEN IF IT'S NOT USED TO CUT ANYTHING! Stainless means the corrosion products won't stick, it does NOT mean it isn't corroding! A 300 series blade needs to be resharpened before EACH dive for it to be useful and not a hazard to it's user.

4. 400 series Stainless Steels are capable of holding an edge long term, and require minimal attention with a stone before each trip. A rinse and dry after each dive trip is generally suitable maintainance.

5. 17-4 PH is good steel, but at H900 (where it holds an edge best) it's pretty brittle. It's not difficult to snap off a shaft tip or thread at this hardness level. I've done it several times. At H700 it's more ductile (as for shafts) but won't hold the same edge. As solution annealed (i.e. as purchased from the supply house) it's not much better than 300 series. It's the heat treatment that makes or breaks this steel.

More data is available here:

http://diverlink.com/gear/knives.htm

 

[MikeS]

Fred,

Thanks for the input. After much investigation I purchased an OMS BC knife http://www.omsdive.com/cuttool.html, which is made by Schrade http://www.schradeknives.com/ It’s made of 440C stainless. The only complaint I have is that corrosion started to form at the point where the handle interlocks with the sheath. The way it’s made makes it extremely difficult to clean and dry. I now use cotton swaps with gun cleaning oil and have not had any further problems.

Thanks,
Mike

 

[Welshman]

Stainless steel will hold a sharper edge than Titanium but my Ocean Master Beta Ti knife is sharp enough. Also I assume that the US Navy would not use similar knives - Mission Titanium knives - for their SEAL teams unless they were up to the job.