Making a fillet knife. I have questions.

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caver101

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Dec 3, 2010
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I am looking at making a few fillet knives as Christmas gifts. These knives will see a lot of use from saltwater to fresh, small fish to large. Not looking to build a show piece, but a functional hard working fillet knife.

First I started researching steel. Well, looks as if there are 1,000 different opinions on what steel is best for a fillet knife and you guessed it...none of them are the same. I see quite a few people like carbon steel too. I see different opinions on thickness and stiffness as well. Below is a list of questions to help guide my research process. Any help would be greatly appreciated as there are not a ton of fillet knife topics in the archives here.

What my requirements are:
Thickness somewhere from 0.060" to 0.080" I am going to guess 0.075" would be about ideal.
Stainless is a must.
~8" cutting edge (But would like to make a couple 10" for the larger stripe & kings we catch)
Handle material: I like blasted canvas micarta, but have seen a lot of discussion about horse trailer mats as being very good and "grippy" on a fillet knife.

Questions:
Steel: Being very new to knife making I am completely lost on this, if it was a skinner/hunter I would know exactly what I wanted to do - but with it being a fillet....well...my ignorance on the topic is shinning bright :D. I know the knives must be stainless to put up with the abuse they are going to receive. I have a Knives of Alaska "Steelheader" in 440C that is a good knife, but I would like a little more flex out of it (its ~0.085" thick). I have the common Walmart Rapala $8-$25 fillet knives of unknown steel that flex really well, but dull fast. So with that being said, I think I have talked myself into using 440C as a good mix of stainless and cost for my first fillet, but I am open to suggestions.

Steel hardness: Completely lost on this one too. Depending on the steel, (for talking purposes lets say 440C) what would be the best hardness? I have seen the numbers 58-59 spoken of in old post. What is a good mix of edge retention and flexy?

Steel source: Since I only am capable of building a knife via the stock removal method I am having a heck of a hard time trying to find surface ground steel in anything close to the thickness of what I need. Any suggestions for a source?

handle material: I think I really want to try the "horse trailer mats". We use them as target backers at our rifle range and I think they would be very "grippy" when wet on a fillet knife. My question is what is the best way to attach and shape it?

I would love to hear advice, tips, hints and anything else anyone would like to share with me.

Thank you in advance for your time!
 
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This is a photo that "Last Visible Canary" posted of a Busse Fillet. This is very similar to what I want my end result to be.

Fillet-and-Sheath.jpg
 
You didn't mention grinding or heat-treating; what equipment do you have? If you have a belt grinder I would advise drilling your tang holes, cleaning up the surfaces and grinding the profile, then HT, then grinding your bevels. If you only have files etc to work with, you'll have to do almost all your stock removal before HT; with pieces that thin it could lead to warping in the quench. I recommend Peters' HT, they are very picky about keeping things straight and clean.

Steel: "I think I have talked myself into using 440C as a good mix of stainless and cost for my first fillet, but I am open to suggestions."
I would go for CPM-154 or CTS-XHP, but 440C is a fine choice for exactly the reasons you state. It's not the very best stainless available, but it still makes a darn good knife and is less expensive.

Steel hardness: 58-59Rc is a very good hardness for 440C. The flexibility will depend on how long and thin the blade is.

Steel source: Check with Aldo , usaknifemaker, and pops knife supply. If you can find precision-ground stock, it's worth it.

handle material: "horse trailer mats". They can be epoxied and pinned just like micarta or wood. When drilling for pins, drill a little and back off, repeat etc. Keep the bit wet with soapy water, it helps flush away the little bits of "rubber". I've heard of people using Barge cement (like you use for leather work) without any pins and they say it held up very well. You won't be chopping with these knives so you could probably get by without any pins or bolts.

They can be shaped on a belt grinder or with sandpaper wrapped around a bar. Don't try to get too fancy, it doesn't shape as nicely as more solid stuff. It's not very pretty but it's definitely grippy and comfortable.

Basically, you've already answered your own questions :)
 
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james terrio said:
Steel: "I think I have talked myself into using 440C as a good mix of stainless and cost for my first fillet, but I am open to suggestions."
I would go for CPM-154 or CTS-XHP, but 440C is a fine choice for exactly the reasons you state. It's not the very best stainless available, but it still makes a darn good knife and is less expensive.

)
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With regards to steel, why not consider going up to the ones James mentions above?

Compared to the price you will pay shipping it to you, steel is cheap & will make the difference between good / great performance.
 
Thank you for the speedy reply!

I am unable to do my own heat treating, that work is sent out and Peters is the one that will do the work for me.

I use a belt grinder for shaping.

I had not looked at njsteelbaron, I will give him a look and see what I can find.

Thank you for the tips on the horse matting!
 
440 C is a good choice, I use precision ground 1/16, profile the final shape prior to heat treat and grind the bevel after heat treat. I dont know if the stall matt is stable in saltwater, some rubbers will get sticky and corrod, I have not tried it but you may want to put a piece in a glass of water with salt and see if the texture remains the same. Because the thin steel is flexible I think pins or bolts are needed to keep the epoxy from breaking loose, I peen my pins so they provide a mechanical connection, when the expoxy is setting the only clamping pressure is from the pins, this way I am sure to get a good bond and mechanical connection. Stall matt is different and may not need pins as advised. I think texas knifemaker is the least expensive heat treat if you are only doing a few blades, check them out. 1/16 is really flexible so HT to 58- 59 is fine and will hold a good edge.


Filletjuly-09015.jpg
 
Patrick, thank you and that is a great looking fillet!!! If you don't mind me asking, where do you get your steel?? 1/16" precision ground steel has been impossible to find!

I had not thought about the degradation of the rubber in salt water. Thats something I am going to have to test.
 
IIRC there's someone on this forum who has made filet knives for commercial fishermen. Flex is determined by thickness not hardness. CPM154 would work very well. HRc 60 would be a good working hardness.
 
caver101 said:
I had not thought about the degradation of the rubber in salt water. Thats something I am going to have to test.
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When you run your tests, be sure to put the rubber and salt water out in direct sun -- the combo of water, salt, heat, and ultraviolet is what you're ultimately facing.
 
caver101 said:
I had not thought about the degradation of the rubber in salt water. Thats something I am going to have to test.
Click to expand...
Please let us know what you find, I hadn't thought about that either :o

mete said:
CPM154 would work very well. HRc 60 would be a good working hardness.
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:thumbup: CPM-154 at 60Rc is my go-to stainless. However! CTS-XHP at 60Rc seems to be a bit better both in edge retention and corrosion resistance... it's hard to say for certain, I've only made one knife with XHP. Anyway they're both excellent, and I would call 440C "very good" (as I understand it, CPM154 and XHP are both essentially upgrades of 440C, with somewhat different chemistry and just as important, made by a particle metallurgy process)
 
I need to research it, but does anyone know how much salt I should add to a quart of water to make it similar to an ocean environment?

I will try to pick up one of the mats from my local Tractor Supply in the next few days and experiment with it. I will post results (photos) here.
 
1 1/4 oz per quart is pretty close.

I would have not thought of salt water breaking down rubber either.
 
As far as steel goes, I think I would go with N690CO. It seems that it is meant resist corrosion, and is the closest thing to H1 that we can get. they have it at alpha knife supply.
 
I have made over 200 of the style posted in 440C, CPM-154. I have never had one returned with corrosion problems. Unless you want the hype factor, fancy corrosion resistant steels are a waste on a fillet knife.

Neoprene/horse stall handles work well. Use the black and flexible epoxy made for bonding rubber to metal. Three Corby bolts will be all that is needed for keeping everything in place. Use them to snug the neoprene down just tight enough to leave a little epoxy between the tang and scales. Slightly hollowing the back of the scales before applying the epoxy assures a good bond.
 
bladsmth said:
I have made over 200 of the style posted in 440C, CPM-154. I have never had one returned with corrosion problems.
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I haven't made that many knives total! But I agree... there's a point where if a steel has greater than 14% chromium, which all of these do, you're going to have to try pretty hard to get it to rust. When I speak of XHP being a little more corrosion resistant than CPM-154, I'm talking about taking knives camping, wading with them, leaving them dirty in a soaked leather sheath for days at a time in hot weather, and barely finding any corrosion. (like a couple tiny pits being better than none at all). Mind you, there's no salt water where I live... I will mix up some up with the Count's formula above and set a couple blades in there to see what happens.
 
Put the knife on the beach in Padre Island TX ,that would be a really good test !!
 
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