More destructive testing

[Mark Van Loon]

A week or so ago i posted pics of my first destructive test to this blade

before

after the 90 degree flex

well i went ahead and bent it back straight and then 90 degrees the other way. it made it and didnt crack, so i decided to go ahead and see what it could take. it went 180 degrees 11 1/2 times before cracking. now im a little suprised by this so i go back to my notes, this was a stock removal blade, 1084 steel clay coated water quenched, tempered at 350 for 1 1/2 hours. i normalized this one 3 times, once after profile grinding, once after grinding the bevels and one more time after draw filing and getting the blade all ready for heat treat. i used those hardness testing files after heat treat to get an idea of relative hardness of the edge and spine, i came up with around 57-58 for the edge and 36-37 for the spine. im wondering if the near dead softness of the spine contributed to the ability of this blade to flex to 180 degrees so many times??? here is a pic of the blade after 14 180 degree flexes

the crack is kinda hard to see but its 1 1/2 inches from the tang of the blade, right at the bend point.
the crack opened up more between 11 1/2 and 14 flexes. i wanted it to break so i could get some pictures of the grain but it hasn't given up yet. how do i get this thing to break? i want to see the grain and compare it to one of my failed blades. also does it sound like im doing something wrong here? i really never expected it to perform like this so im wondering if i goofed somewhere. please post comments and opinions, im a little puzzeled here

 

[B . Buxton]

Mark,

If the edge holding ability when slicing and chopping was as good as the bend test, I would say fantastic. Strength isn't worth much if it won't hold an edge, unless your making prybars. But at a 57-58 RC I would say it will. Great job, now go make another one. Fun isn't it.

Bill

 

[Mark Van Loon]

before i bent it the first time it chopped through 1 2x4 and still shaved hair, but it did dull just a bit from fresh sharpening, i wish i would have had some rope before i bent it though. i did drop it from about 5 feet on to a concrete floor, once point first, the other edge first, to see if it would chip,... it just put 2 nice gouges in my basement floot though.

 

[Jason Arnold]

im wondering if the near dead softness of the spine contributed to the ability of this blade to flex to 180 degrees so many times???

Yes.

I used to do that, but now put my blade bodies in the mid forties, plus, a hardened spine. Very hard to bend them. Have to have a cheater bar, and still remains difficult. Real nice job on that hamon by the way, look forward to seeing more of your stuff, looks like you pretty much got it down.

FYI, heavy flexing and then a snap, will give you a distorted view of the grain because of plastic deformation. So, you got to look close in the areas that saw the least amount of twisting and stretching. Lastly, expect the softer portion to appear coarser than the hard. Keep up the good work.