SS Fillet HT

Matt de Clercq

Matt de Clercq

Well-Known Member
I heat treated a 14" AEB-l fillet knife that is .125 thick and it won't come back to center when flexed. It seems to me that I need to adjust tempering temperature but I don't know if the blade should be harder or softer. I tempered twice at 400 for 2 hours. Any help would be greatly appreciated.
 
how did you first harden it, and did you test it before tempering? once in a while i miss the hardening and the blade is just too soft so i have to try again.

Erik
 
How far do you flex it? To decrease the chance of taking a bend, increase the hardness (strength). However, 0.125 might be too thick. It depends on how far you expect it to flex. Also, 14" blade or 14" overall?
 
cnccutter said:
how did you first harden it, and did you test it before tempering? once in a while i miss the hardening and the blade is just too soft so i have to try again.

Erik
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I don't have any fancy tester but my 60 RC file skated and no penetration with a quality drill bit. To the best of my knowledge it got hard. I did a dry ice/denatured alcohol treatment before the temper cycles.
 
me2 said:
How far do you flex it? To decrease the chance of taking a bend, increase the hardness (strength). However, 0.125 might be too thick. It depends on how far you expect it to flex. Also, 14" blade or 14" overall?
Click to expand...

14" over all. I didn't think about the steel being to thick. I flexed pretty hard. Harder than a salmon would. I'm "attempting" a ht of the same model but .70" think as I write this. I'll do everything the same and see if the thinner steel has any memory. One way or another I'll learn something today. :)
 
Flex is about geometry, not heat treat (for the most part.) A heat treated blade will take the same amount of force to bend as an untreated blade, but the untreated blade will take a set sooner. 0.070 may be on the upper edge of thickness for a fillet knife. I don't have a lot of experience with fillet knives, but I do make kitchen knives at 0.070, and they aren't too flexy. You could probably go to 0.050 and possibly thinner. Hopefully someone else will chime in who does fillet knives.
 
I made a petty from 1.6mm (.063) 1.2519 steel (never have tried a fillet). It has some flex to it, not a whole lot tho. I can tell you that .063" would still be too stiff for a proper fillet knife, IMO. I would use the .050" stock or better, as Warren the Amazing Aspiring Martian mentioned.
 
Just to offer a dissenting view, we get sent fillet knives between 1/16 to 1/8+. We sure don't do any 90 degree bend tests, but they seem to flex OK. Really long, very thin blades tend to warp in HT and when flexed, they return to perfect warp. ;) Takes some doin' to straighten them out.

Rob!
 
Matt,
I might have missed it, but did you grind the knife before or after HTing? It sounds like you ground the blade first?

I'm not a super experienced fillet knife maker since it's probably the kind I make the least of.

Try doing your profile. HTing and then grind in your bevels with a lot of distal tapering on .70 stock.

I have made several of what I called my Pacific Yellow Tail swords this way with a 9-11" blade. The worked fine with just a little flex. I used 3/32" stock.

I agree that in my experience, flex comes from distal tapering and design, not the HTing.

The few Bass 2-10lber fish Fillet type knives I have made, I started with 1/16" 440C They worked fine. I just hate making them! LOL
 
SUCCESS! I heat treated two .70" thick blades today and they both flex and come back to center perfectly! I am surprised they don't flex more than they do but I think I'll get a little more out of them when the bevels are ground. Thank you for all the help.

The poor .125" blade that I started with is now my wife's (second one this week). I decided to practice my wire inlay in some curly maple.
 

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Matt - that looks good. I plan to keep my wife from seeing your wire inlay - she'll be wanting me to do that!

BTW, you have mentioned .70" several times - I'm assuming you do mean .070"?

Ken H>
 
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