The results of my latest flex test are?

From all ive heard, 52100 isnt the best steel to be playing with without knowing your exact HT specs, etc. Simply using a magnet will tell you when it reaches nonmagnetic, but wont help with overheating, soak, etc.

When i read this:
"The heat treatment of 52100 is different than that of many of the other alloy steels, including 5180, in that the hardening temperature controls the amount of Carbon that dissolves in the austenite - the condition of steel at high temperature where it is a solid solution of Iron and Carbon.
This gives a finished blade that has lower banite - a transformation product that forms at the lower temperature than martensite rather then tempered martensite - the hardest form of steel.
When overheated for the quench, most alloy steels simply have coarser grain, but 52100 will develop a weak structure. "

I would assume exactly what it says....too hot when it hit the quench. Have the same piece sent out for professional HT and see if you see a difference
 
Ah, I see what jig you are talking about now. It is an interesting device. With a fair amount of math, you should be able to determine the actual force for bending the blade. This seems to be a neat gadget, but you are actually measuring the torque on the bolt head, not the torque on the steel. then there is the angular forces, how high form the vise, how far from the center of the blade, and are you bending the blade through tension (pulling on the side of the bolt) or compression (pushing from the side of the bolt) steel has a higher compressive strength than tensile strength, it may change the reading on the torque wrench.

:) I know, it may be a bit of work, but then probably none of us can afford the testing equipment my Dad showed me at Snap-On. they have a way to test the wrenches to failure that I thought was amazing (I was 12 at the time) they set the wrench in a fixture that was in front of a wheel, which had the same center as the fixture. a peg was set into one of the holes in the wheel, and then the wheel was turned against the wrench. a computer kept track of force required, and degrees traveled. when the wrench was about to break, I was able to see the dip in the force right before it broke on the printout. I would love to have a set up like that myself, unfortunatly, I don't have the wallet :( but a few charts and calculations can get pretty close.

Good luck
Ken
 
Kevin R. Cashen said:
Karl, you would be a good guy to ask about this, on the "180 degree" bend do you take the tip beyond 90 degrees until it actually is 180 degrees and parallel or even touching the tang? Or is this test actually just two 90 degree bends in opposite directions?
Click to expand...


Correct - two 90 degree bends, full parallel with the floor one way, then turn it around in the vise, and then full parallel with the floor the other way.
 
After all I have seen, and messed with for a few years now, I'm just happier knowing my blades are fully hardened.
I'll temper them for their intended use. Maybe draw the spine back some.
If someone can break one of my knives, I'll just call him "Sir".
 
hmm... to measure the torque required, why not just get a long sparking plug socket, hacksaw and file a slot through it to take the blade, and weld the open end shut with a filler plate to keep the strength so the two sides don't bend.

then with the tang in the vise, just drop the plug socket down the blade, clip the torque wrench in and start pulling.

I'm assuming here your torque wrench is like mine, which is similiar to a socket set wrench but longer, with a square bit that clips in to the hollow square bit in the base of a socket. If yours look like a crescent wrench or a pipe wrench it probably wouldn't work.


as to the screwdriver suviving being a step up a wall but bending against the car engine. Thats the difference between Sheer force and Bending force.
 
IronWolf said:
Allan, Assuming the steel and geometry are the same, a edge to back hardened blade and a edge hardened blade will both will flex the same, until the edge hardened blade reaches it's yield point, at that point it will bend, while the other blade still flexes, and will return to true, it will take more force to break the fully hardened blade than it would take to bend the other several times.
Click to expand...
I believe what i should aim for is a blade that will not break, but takes a lot to bend.

Lets pretend:
Lets say that based on my test yesterday that 65 ft lbs of force will break one of my fully harden blades.

This would seem to be a type of upper limit then?

The thing I would want is to be able to design some type of heat treatment that can bring me a final blade that will be very hard to bend, but will not just snap off at 65 ft lbs like a fully harden blade.

Some how I got to believe that there is a way for me to learn to Heat treat a blade that brings the best of both parts of the world of hardness to me.

Not a fully soft blade, (That would be silly as the edge would not last long), I dont want it to bend over just by looking at it,
But not so fully hard that it snaps on me too just because I crank down on it with 65 ft lbs of torque.....
 
Kiwi303 said:
as to the screwdriver suviving being a step up a wall but bending against the car engine. Thats the difference between Sheer force and Bending force.
Click to expand...

OK,,,,ummm...whats the difference?
If I stuck my knife from yesterdays test into a bench vise I think I could have stood on it with no problem.
I weigh about 200 lbs, so that would be 200 lbs of "dead weight" right...is this "Sheer Force"?

I put the knife in the vise and the real torque wrench gave me the reading of 65 when it snapped.
Is this different than 65 lbs of dead weight?..

I think it HAS to be, because adding 65 lbs of dead weight to a knife in a vise is nothing.....any knife could handle that weight right?

Whats the difference?
 
Using your torque wrench the way that you do may not mean any exact number to the rest of us, but it is certainly a valuable test in your shop as long as you repeat it exactly with every knife you test. The exact ft. lbs. of torque doesn't matter as much as being able to guage differences from blade to blade, which your setup will most certainly do.

Todd
 
IronWolf said:
With a fair amount of math,
Click to expand...
Errrr....we got to find a "No math at all" test...LOL

IronWolf said:
but you are actually measuring the torque on the bolt head, not the torque on the steel....
then there is the angular forces, ...
how high form the vise, ...
how far from the center of the blade, ...
and are you bending the blade through tension...
or compression ...
Click to expand...
Yes, all of the above is more than likely very true.
So, I guess we have to just say that the torque wrench is like a "Universal Constant", (in other words, the results of my torque wrench test are an unquestioned fact of the natural world...and can be compared with the data that you may come up with with your own torque wrench.)

If we assume that the torque wrench test as shown in the knife mag BLADE is universal in it's true results,...then we can also assume that if you were to test a knife with the same type of torque setup we can compare the results.

A lot of assumtions I know, but you have to just go with it so that you can try to compare one knife and HT system to another across the country or years into the future.
 
Allan Molstad said:
.....

I would like to know if anyone else that works with 52100 has been able to bump a blade up well over my limit of 65 ft lbs, and not had it snap?

I)
Click to expand...

Isn't the ft lbs number going to be consistant with steel mass?.....In other words, given two identical blades, one annealed and one fully hard, the amount of force (ft lbs) applied to flex ( elasticity) should be the same?.....(my understanding of post #59 in the Basic Curve thread).


A fully hardened / tempered 52100 blade can be made to flex to 45 degrees and spring back without any additional softening of the spine.........or it can be designed to flex to 90 and spring back to true again.........or can be designed to remain bent ........Its a case of deciding where you want the yield point to be and then choosing the h/t method that best suits your needs.
 
Allan Molstad said:
.....


If we assume that the torque wrench test as shown in the knife mag BLADE is universal in it's true results,...then we can also assume that if you were to test a knife with the same type of torque setup we can compare the results.

A lot of assumtions I know, but you have to just go with it so that you can try to compare one knife and HT system to another across the country or years into the future.
Click to expand...


How can you compare one knife with another if the size/dimensions are not absolutely identical?.....and if they were identical (an unlikely event), but the heat treatment was the only determining factor that was different, then would not the torque results be identical?

btw..theses are questions, and not answers:)
 
Kevin Davey said:
How can you compare one knife with another if the size/dimensions are not absolutely identical?....
Click to expand...
We have to go with the flow, and try to get as close as we can.

EXAMPLE, lets say you post that you just did my same test with the same type of knife.
Lets also say you got to 100 ft lbs on your torquewrench before your blade bent over but did not snap.

I would really like to know how you got that out of your blade?
....
The torque tool give me a "good enough" way to compare my blades to your blades...("IF" we jump to assumumtion that our blades were the same everything, and we assume that our wrenches were right down the line the same too.) It's also about the only way I can think of to ever hope to be able to compare my HT results with my other blades and with your's and with blades I make in the future too.

But yes it is very true that we always have to keep in mind that there are many other things that will effect results too.

But a flex test as shown in BLADE that I use is a darn good way to compare results.
It's better that just chopping firewood, or banging the knife on stuff to check hardness.
 
Allan Molstad said:
We have to go with the flow, and try to get as close as we can.


Lets also say you got to 100 ft lbs on your torquewrench before your blade bent over but did not snap.

I would really like to know how you got that out of your blade?
....
.
Click to expand...

By having a blade with more steel mass.
 
Kevin Davey said:
In other words, given two identical blades, one annealed and one fully hard,.
Click to expand...
What Im out to test is not just the ability to flex a little and then return to straight, any knife and any HT can do that.

Rather what I think is a better test is to find a way to get a knife that will not fail.
If a knife bends too easy? ,,, it fails
If a knife snaps on you?...it fails

I want a knife that does not bend very easy at all, and will not snap .
 
Allan Molstad said:
I dont know for sure, but I think 1/4 inch is about as thick as I can go without the spine looking a bit funny...

so I think that 1/4" is the upper limit of thickness for me.
Click to expand...

I think there may be to many variables to make comparisons, even if spine cross section thickness were all identical. ....

... types of grind (flat, hollow, convex etc) , variations in heat treating (ie grain size) , differences in alloy and carbon content of the blades etc etc

btw...its good to discuss these things..and I wish you every succes in your journey.
 
Here is Ed Fowler's set-up for a torque wrench attachment if you wanted something to go on and duplicate so if you were interested in this sort of testing you could all have similar equipment.



IMGP0653-1.jpg


IMGP0655-1.jpg
 
I've come to the conclusion some of us spend 95% of our time trying to solve 5% of the problem...
 
sheer is a sideways force that involves the structural ridgity of the steel, bending is an angular force that flexes the steel around a point.

scissors sheer paper, with two blades sliding past each other.
 
You must log in or register to reply here.
Back
Top