Performance

H

Hesparus

Joined
Oct 31, 2004
Messages
1,442
I'm trying to figure out how to squeeze some more performance out of my knives. I'd like to be able to make knives that will, as I keep hearing about, be able to cut the door off a car. I recently tested a few knives that I made a while ago on a steel drum. I hammered them through the side of it and then chopped at the rim a bit. Every one of them lost their tips immediately and shorly after lost bits of the edges. One was 154cm (tempered to 1000 degrees) one was 01 (tempered to 370 degrees) and one was 5160 (which I didn't temper. It was such a crappy knife that I figured it wasn't worth the extra half hour to temper it. That said, I know exactly why this one failed to perform.)
After, I put them in a vice and bent them a little. None of them deformed (especially not the 5160, which is 1/4" thick) and none of them broke (I didn't try THAT hard to break them but they were all real tough). The 01 and 154cm were flat ground and the 5160 was cannel ground.
Do I need to temper these at a higher temperature (or lower for the 154cm), or would a cryo quench do the trick? I work almost exclusively in 154cm, now, so differential tempering is out of the question. Is my choice of steel just bad?
Thanks,

- Chris
 
154CM, while a fine stainless steel, is not particularly tough. I would pick a different steel, if destroying car doors is what you have in mind.
 
Danbo said:
154CM, while a fine stainless steel, is not particularly tough. I would pick a different steel, if destroying car doors is what you have in mind.
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for that frame of words I for one think different :(
but
thickness and edge geo will be your biggest aid here, if you want a chisel heat threat and grind it like one. :)
 
Your biggest aid to knife performance is to design the knife for the intended job. A general purpose grind will only handle general tasks well, not specialty tasks like cutting car doors.

Use a convex or chisel grind for that type of usage, forget hollow or flat grinds. Grind the tip to a broad thick spear point, forget about cute little clip points, they are not as strong.
 
Look at Rodgers Hurricane knife. It has a wide blade and point. I don't know what kind of grind he used but I put a thin convex grind on mine. There are a lot of things this knife won't do well, but for a general use knife, it's tough to beat.

There is no such thing as a perfect design or perfect steel. That's why most of us have a box full of knives.
 
I use 5160 exclusively for my blades, and they WILL cut a car door off its hinges without breaking..flat ground too. Edge harden in 400 degree quench, hold until entire knife is cooled to 400 degrees, then immerse the whole knife in the quench and hold the quench at 400 for 4 hours. Cool knife, and temper again at 400 degrees for 2 hours. Draw the first 1/2 inch or so of the tip back at 475 degrees. The result is a blade that is bainite with some retained martensite. Very very tough, and same hardness as if the blade were tempered conventionally at 400 degrees. If the blade was forged, make sure it is thermocycled to reduce grain size before heat treat. Blade done in this manner should bend roughly 45 degrees without cracking, and typically over 180 degrees without breaking.
Give it a whirl, and have fun
 
Why do you want to cut through a car door? Just because someone tells you their knives are better because they can cut through a car door doesn't mean they are. I could tell you that I could pry open a locked car door with a knife, but that would mean I have simply made a crowbar with an edge, which isn't good for anything but being a more dangerous crowbar.
 
Bump that 370 degree temper on the O1 up to around 425 and you will have much better luck. 370 wouldn't give you any noticeable difference from the as-quenched hardness of O1 (very brittle).
 
yeah, I do agree that there is no need to cut through a car door, or any other metallic objects. (other than opening the occasional tin can)
Look for intended use, and design then to fit it as well as possible without compromise.
 
MinnesotaSlim said:
I use 5160 exclusively for my blades, and they WILL cut a car door off its hinges without breaking..flat ground too.
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I for one, would really like to see that done :) mainly because I've never seen it done,, we hear about it ,, please show me/us :) I assume that the knife would still look like a KNIFE afterwards and still be useable :confused: {pictures are worth a thousand words you know..come on guys .. Pictures.. :)
 
chair_hole.jpg

This is what I have done to a folding chair. Thicker metal than on a car. It took about 8 min with VERY hard wacks with a 1 x 4. It did not break the tip at all and the dents in the edge started to grab the seat which made th dents chip out some. I was impressed to say the least. All from the torch HT Dan :D
 
Larrin said:
Why do you want to cut through a car door? Just because someone tells you their knives are better because they can cut through a car door doesn't mean they are. I could tell you that I could pry open a locked car door with a knife, but that would mean I have simply made a crowbar with an edge, which isn't good for anything but being a more dangerous crowbar.
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Probably because this was one of the tests used in a magazine. The scenario was to prove if so called survival knives are useful in urban situations. Trying to cut through a car door is for what if you're in a car accident. Wherein the doors won't open because they're deformed, would your survival knife be able to get you out of it?
 
I've done a lot of sharpness testing...but never on a car door.

Is there a real need? How many people die because they can't break out of their car door? (one that would be able to be cut with such a knife....by a person who is not already dead or near-dead, of course)

Seems far-fetched to me....

But what the heck, it's all good, right?
 
cramnhoj said:
Probably because this was one of the tests used in a magazine. The scenario was to prove if so called survival knives are useful in urban situations. Trying to cut through a car door is for what if you're in a car accident. Wherein the doors won't open because they're deformed, would your survival knife be able to get you out of it?
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It would make sense that this would come from a magazine, with the quality of information that is most often printed in the magazines, I think a better test would be to see how many magazines one could cut through ;). I am sure I am not the only one here that also does some firefighting and rescue when not making knives. I have cut up my share of vehicles, with Hurst tools. I can safely say that when you are all banged up in a crumpled up car, beyond cutting the seat belt, a knife would be as useful as your ball point pen :( . If you have one of those 80's style survival knives ,with really jagged saw teeth on the spine- go for the windshield you will be out in no time. If all the windows are too smashed up to get you out- you are in no shape to even move on your own.

This type of marketing has always been funnier than a cartoon strip. Scare the customer with a wild@$$ed scenario that there is less that a .5% chance they will ever see, outside of hollywood - "if you are ever doing a low level jump behind enemy lines and the parachute cords get caught on the plane and you are being dragged throught cactus and you have to quickly cut yourself free before the forces of evil show up in tanks and you will have to hack off one the of the armored doors to get at them, and then plunge your blade thought their body armor without it getting hung up... :rolleyes: " Please! How about a knife that looks good, can cut up harder wood for clearing a camp and starting a fire, clean some fish, skin and bone out some venison without making ones hand ache and then be sharpenable. That seems to be getting rarer in these days of high end crowbars.

Besides, what has a greater chance of happening- cutting yourself out of your wrecked car, or having the nice officer, who pulled you over for a simple traffic violation, suddenly wanting to call for backup when he shines the flashlight on your Jim Bowie survival tool? That is real life :(
 
Is there a real need? How many people die because they can't break out of their car door? (one that would be able to be cut with such a knife....by a person who is not already dead or near-dead, of course)

I tend to agree Daniel and Kevin beat me to the real issue. One thing I have stressed to my family, is to have something to break the window or windshield. I designed survival tools that will do that plus pry and cut. One is in each vehicle.

During the flood this year, one woman did die in her car because she couldn't get out. These city people don't seem to realize that if the electric system shorts in their expensive cars, the windows won't work and the hydraulics will not allow them to open the door if the car is submerged.

We had one idiot police officer here that was racing around a parking lot, ran his car in a detention basin and drowned because he couldn't open the door. I still haven't figured out why he didn't just shoot it out but that certainly cleaned up the gene pool.
 
On the Gadgets & Gear section I had asked about breaking glass recently and things like a spring loaded center punch work well.
 
blgoode said:
This is what I have done to a folding chair. Thicker metal than on a car. It took about 8 min with VERY hard wacks with a 1 x 4. It did not break the tip at all and the dents in the edge started to grab the seat which made th dents chip out some. I was impressed to say the least. All from the torch HT Dan :D
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.

dents that chip out some :eek: :D

so if trapped in your car you'll need a 1x4 also :confused: do we need sheaths for 1x4's ? :confused: :D :D
 
I just headbut glass out myself. Broke a 2"thick piece of porthole glass in Cuba once. Ahh, miss the good old Navy days.
 
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