Temper of fillet knife

[Rasmus Kristens]

hi guys

So i have an issue..

I was tempering my fillet knife for the 2nd time, and accidentily set the oven to hot air instead of regular top/bottom heat... That turned out pretty hot.

So what can you say about this temper? I will still finish the knife, i ask just to learn :-)

[Crex]

Actually that doesn't look too bad. Was the setting around 400? A lot will depend on the steel you used. If it's a "stainless" steel, can make a big diff. Hi-carb forgable should be ok.
Sharpen and try it out for edge retention and flex (before mounting a handle).

[Rasmus Kristens]

Its of 90crv2 steel, it was set to 410 F i guess it reached somewhere around 445-455 F.

[Rasmus Kristens]

whats the best way to test retention? Just cut a lot of stuff and see when it gets dull?

[WBE]

If going by color, the edge got way over heated.

[Rasmus Kristens]

Originally Posted by WBE

If going by color, the edge got way over heated.

that was exactly my thought at first. But when i look at temper colour charts, that colour happens at WAY higher temerature than the oven could possibly reach on the settings it was on.

[Rasmus Kristens]

i think i did an edge deflection test :-)

I put an edge on the blade and dragged it across a brass rod. I could see the edge deflect against the brass, but the edge didnt deform and it didnt crack.

How much pressure should i put on the blade when doing this test? I left some very noticeable scratches in the brass.

[Crex]

Reading surface colorization from heat is not a very accurate way to determine much. Different steels react differently. With 80crv2, 400 is good ballpark temp to start testing results.

If the edge flexed and did not crack but came back to straight, you should be ok. Yes, sharpen and cut different things like cardboard, shave some wood, etc. - all the things you would normally do with a blade. If it dulls quickly you can redo the hardening quench with this steel and try again on the temper draw at a lower temp.

Just remember most try to achieve a flexible blade on fillet knives. A lot of that has to do with distal taper geometry.

[Rasmus Kristens]

Thanks crex. It has a distal taper, but the blade is made from a 0.12" thick scrap knife blank i had laying around.
Because of the thick stock its quite stiff.


high quality gif upload

But im happy with the result, also because its the first time i freehand grind a knife on my belt Sander.

[Crex]

Yeah that's pretty thick on out into the working area for a fillet. More like a boning knife (I prefer that on bigger fish).
Sounds like a good excuse to go catch some fish and put to task as designed. You'll know for sure after the first 5 or 6.

Note: If you do decide to re thermal cycle the blade, make sure you go through the normalization process prior to hardening quench.