Talk to me about.... FILLET KNIVES!

Drew Riley

Drew Riley

Well-Known Member
A buddy of mine at work wants me to make him a fillet knife. To be honest, this isn't really something I've ever considered before, and I'm not really sure how to even approach it.

1st off, I'm leaning towards a high carbon steel.... PROBABLY 1095, as that's what I'm most familiar with heat treating. I'm thinking forced patina as well, just to help inhibit rust a little better.

How would I heat treat/temper something like that?

I mean, obviously I want flexibility, but I also want toughness too. Anybody ever make one? How did you approach it?
 
There's a reason why many of us don't make fillet knives.....they are MUCH more difficult and time consuming, then the money you can get out of one.

In my experience, it's complicated to get the combination or thinness, flexibility, and a level of hardness that will hold a decent edge. The majority of the problems I have had were in grinding and heat treating....once you get less than about .070" blade thickness, simply grinding on it, in either the annealed or hardened state will make it warp...sometimes very badly. I "sorta" solved that part by building a "backing plate" of 3/8" aluminum....the blade is affixed to it, and the aluminum keeps the blade from flexing while grinding.....this in itself brought up another issue for me.....not being able to feel the heat when grinding.....and at less than .100" thick, you can burn/wreck a blade real quickly.

My advice would be to do ALL grinding AFTER heat treating. I can't speak to 1095, as I've never tried it for a fillet blade, and don't care for it anyway.....but I can tell you that I've done several fillet blades out of .100" thick 15N20....taking them down to .060-.080 and they have worked well. Heat treat wise, I did it with just the profile, hardened as I normally would, but pulled the temper at "2 steps" higher than I would normally (I would normally temper a 15N20 blade at 375-400F.....with the fillet blades, I took that temper to 450F......it will sacrifice a bit of hardness, but that was where I had to go to get the flexibility I desired. If you've not built any fillet knives prior....be ready for some experimentation, and a little frustration.....there are a lot of "little" things that you'll run across, and have to figure out versus building a standard "hunting" knife.

Here's a pic of one that I built of 15N20, and took fishing in Vancouver, BC......at the end of each fishing day, we usually had 1-2 hour of fish cleaning to do....and I would normally have to sharpen it at least once during each cleaning session. This one has a 10" blade (which was kind small for most of the jobs) and stabilized cork handles.

(I like to call this one "I FOUND Nemo!" :)
Day9IfoundNemo.jpg


This is what an 88lb Halibut looks like after meeting the fillet knife....
Day13Halibutfillets.jpg


This is what that halibut looked like BEFORE it met the knife....
Day13Edwith88lbHalibutlightside.jpg
 
Ed, Nice looking knife and awesome catch brother. That had to be a fun time!!

I have made many and agree with you. There a PITA and often times you will have more time into making them. But its also a great and fun adventure learning to grind on thin stock. If it were me. I would make 3 blades. Heres why, Your probably gona mess up one, either in HT or grinding. Then you will make the one for your buddy, and will want to keep it for yourself!! :D

I also harden them Before grinding and I do not take the steel down further when I temper. I temper per my normal for whatever steel I am using, I have made O-1, 1090, 15-n20, L-6, Carbon damascus and currently am working on 20 in CPM 154

Heat treating can be a challenge, But, I have found. That if you have a set of cooling plates it helps me to get straight blades. What I do on carbon and tool steels is, after they come out of the initial quench. I quickly make any adjustments to the blade by hand. Then put it in between my quench plates to cool the rest of the way. Im not 100% sure if this effects the steel in any way other then to help keep it straight, But so far its working good for me. This little step has helped me to get much straighter blades and makes less work trying to get them to straighten during temper cycles.

I do full flat grinds on them now. I use to do convex. but found a flat to be better. Both will work, but flat gives more flex to the blade in my experience.

Good luck and have fun. Keep us posted on your progress. Im sure there are many who would enjoy seeing how this turns out!
God Bless YA
Randy
 
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Ed,
Unfortunately, while at work, I can not view most pictures, but I will definitely take a look while I'm on my home computer.

I've pretty much already decided that I'm gonna heat treat BEFORE grinding, as I'm sure I will have enough issues with such a thin stock wanting to warp as it is. Besides that, at least it will spring back (hopefully) when is start grinding the thin parts.
I also figured that I was definitely going to need a backer of some kind. I've had enough trouble grinding 3/32 stock and having it flex on me, much less 1/16" stock.

As for grinds, It's likely going to be a full flat.
 
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I am more comfortable using a Stainless for Fillet knives.
440C, CPM-154, And I have one 10" fillet that I am making for a customer right now in CPM-S35VN.

Yes they are challenging :biggrin: The real problem I have found is what Ed McCaffery noted and that getting paid for the amount of time they take.

The 10 incher I am working on started with 1/8" thick stock and it's going to be a Tuna sword. These I can get closer to the hours invested in sale price.
There are so many of the smaller factory Fillets that are cheap and useable. Also most people seem to shy away from putting out big money on a fillet because they think that they may drop it over the side of the boat.

If you want to go stainless? You are welcome to batch it with mine when I send the to Paul Bos/Buck Knives for Heat treat. Just tell me the Hardness and you want and scribe it on the blade if possible? It will only be about $10.00 or less plus some shipping.

Laurence

www.rhinoknives.com/

www.rhinoknives
 
I've only made a few fillet knives, but I had two interesting challenges.

First was pre-HT resisting the urge to test the flex. :34:

Second was post HT, finding out how much a perfectly even taper affects the flex - (or the lack of even taper)

Grinding post HT would help with both of these.

Rob!
 
I did one a while back, it was from 440C 1/16" steel. I heat treated if i remember right at 1900deg for 15min and then did all my grinding. The blade was 8" long and i convex ground it while cooling between each pass on the grinder. I tried very hard to watch my heat on the blade but my biggest pain was the flex in the blade and trying to get a even finish. ya it was a pain but in the end the blade worked well and the guy liked it, i said i wouldnt do anymore but i am talking with another buddy about a fillet knife for him so there ya go lol :)

I started with precision ground steel so that was a added bonus.
 
I have made some out of 440C 3/32", and I hollow grind. I have mess some up also. The one's I made were around 4-58" which is good for Bluegill and crappie. I just made one out of 1/8" 440C with a 5-3/4" blade for a buddy who took it on his annual fishing trip. Told me it worked great on Cat fish and not bad on crappie, but he wants another with more flex. I grind some before HT and finish up after. I grind slow without gloves to kept it from getting to hot. Which takes longer to make that way.
 
Being an advid fisherman and a lover of saltwater fishing. I can say with out a doubt stay away from your carbons. I have ruined almost every type of steel do to the salt corrosion. The only one I have not ruined is s30v. Which is why it is my fav overall steel. I have introduced it to the deckhands that I know in southern ca and is all they use now. I am planning on trying s35vn for my next fillet.
 
rmbonham said:
Being an advid fisherman and a lover of saltwater fishing. I can say with out a doubt stay away from your carbons. I have ruined almost every type of steel do to the salt corrosion. The only one I have not ruined is s30v. Which is why it is my fav overall steel. I have introduced it to the deckhands that I know in southern ca and is all they use now. I am planning on trying s35vn for my next fillet.
Click to expand...

Hey rmbonham,

My Shop & Store are in Santa Monica.
You are welcome stop by and say hello if you are ever close by?

Laurence www.westsidesharpening.com/
 
fillet2.jpgI have made and sold about 35 fillet knives over the past 4-5 years. I prefer ATS34 in 1/16" stock. I had problems with them warping during HT if I ground them first. So, I just profile them and drill any holes necessary, then HT. I then temper them to 59-60 RC. Then I flat grind them. My knives are intended for the Walleye as that is what most guys fish around here, so I make them very flexible. A photo is attached. I am just starting to make some stiffer, longer, and heavier blades for salmon and halibut. These are going to be about 16" long overall. I will use the same steel and procedure, but will not make them as flexible. AT LEAST THAT'S THE PLAN.

Good luck,
Milt
 
Milt said:
View attachment 31838I have made and sold about 35 fillet knives over the past 4-5 years. I prefer ATS34 in 1/16" stock. I had problems with them warping during HT if I ground them first. So, I just profile them and drill any holes necessary, then HT. I then temper them to 59-60 RC. Then I flat grind them. My knives are intended for the Walleye as that is what most guys fish around here, so I make them very flexible. A photo is attached. I am just starting to make some stiffer, longer, and heavier blades for salmon and halibut. These are going to be about 16" long overall. I will use the same steel and procedure, but will not make them as flexible. AT LEAST THAT'S THE PLAN.

Good luck,
Milt
Click to expand...

Milt,
It says 440C on the blade? They both work! ATS-34 & 440C.
I prefer the 440C for it's corrosion resistance.

Laurence

www.rhinoknives.com/
 
My first couple were made from 440c. But I changed to ATS34 shortly thereafter. I read on one of the forums, that ATS34 holds an edge better than 440c, but 440c was a "tougher" steel. That may or may not be true. I never took the time to test that premise. Both steels make nice fillet knives. Like we say in MN- "Whatever floats your canoe."

Milt
 
Crucible datasheet for for154CM ~ often regarded as equivalent alloy to ATS34 ~ says 154CM is more corrosion resistant with better edge retention than 440C.

corrosion.JPG

wear.JPG

Obviously, there can be real world differences that can have an affect such as finish, heat treat, and even a bias to our 'pet favorites'. Charts like these - as with most stell data should only be seen as a reference.
 
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From quite a bit of practical experience, 440c is more corrosion resistant than ats-34/154cm by a small margin. I can't tell much difference in edge holding, to be honest. I haven't tested either of the steels with standardized procedures, but I have kitchen knives that I made of both that are basicly identical. After several years of use, the difference in corrosion resistance is minor but obvious, the edge holding isn't obvious. Of course, you really have to be abusing either steel to make either corrode at all, like slicing citrus and not cleaning for a while (my wife isn't the best for knife care, lol). The difference in edge holding might not be noticeable in my home because both knives serve duty as steak knives regularly, and cutting against a hard stoneware plate tends to dull most steels pretty fast.

Also, from their composition, 440c has about 2% more free chromium than ats34/154cm, so it should be slightly better at corrosion resistance. Ats34/154c has about 0.10 percent more carbon so it should be slightly better at wear resistance.
 
Great info fellas and very timely. I have been kicking around the idea for some fillets here lately. Very nice blades btw Milt.
 
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