Steel thickness and flexibility?

S

scherar

Well-Known Member
Can someone give some input about what kind of flexibility you might get from a blade made from .100 thick stainless (such as cpm 154 with a blade length of approx. 6")? I am looking at building a "boning" kitchen knife and need some advice on what thickness of steel to use. From what I have found so far, it looks like .100 is the thinnest cpm 154. I saw some 440C that was thinner, but I would like to go with cpm 154, 154 cm or ats 34.

Secondly, what kind of issues must one contend with during HT in order to make a knife that is flexible but strong? I know warping can be one. I haven't played around with flexible knives yet (fillet, boning) so I am trying to gather all the facts I can before I order steel.

Thanks.
 
As far as I know, flexibility has a lot more to do with thickness and geometry than hardness. Meaning, you can make a filet or boning knife good and hard for edge-retention but it will still flex. Most people who make blades less than 1/8" thick just profile them drill their holes and then do all the bevel/taper grinding after HT to avoid warping. A stress-relief cycle after profiling couldn't hurt any; it's pretty easy to build up heat (and probably stress) on something that thin.

CPM-154, though one of my favorite steels, is known for having a good deal of "mill scale" on it, and some pitting under that. By the time you surface grind it to remove that, it may be several thou thinner than the .100" you started with.
 
Do you want the knife to be flexible like a fillet knife ?

1/16"= .062 = VERY flexible
.100 will by comparison be only marginally flexible.

You'ld probably be best served to go with the .100 cleaned up to around .090 with a full length distal taper. This way it'll be fairly stiff in the first 1 1/2" in front of the handle but gain flexability out to the tip. Going this route you should be able to adjust the amount of flex to your taste by the amount of taper.

To avoid warp profile your blade from barstock then heat treat and plate quench and grind your bevels after HT. I just did one in 1/16" ATS-34 and it came out straight as an arrow.

I found that grinding that thin stock to be a tricky affair, LOL. My blade length was about 3 1/2" so I stuck a welding magnet to the back side to prevent blade flex while grinding.

Good luck ! Josh
 
I have made several fillet knives from 1/16" 440C, and yes warpage is a problem, my next 2 will be profiled and drilled, then heat treat, then grind the bevels. As far as the heat treat, I treat just like any other knife made from 440C, and they have good flex. As Josh said, grinding that thin is tricky, especially on a 6-1/2" blade.
Dale
 
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