— How Does One Ruin the Temper on a Knife?

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stoffi

Joined
Jan 14, 2008
Messages
967
Hi,

I'm wondering how the temper on a knife is ruined. At what degrees does a temper start to change on a manufactured knife, for example?

Does boiling water ruin the temper on a knife?
 
stoffi said:
Hi,

I'm wondering how the temper on a knife is ruined. At what degrees does a temper start to change on a manufactured knife, for example?

Does boiling water ruin the temper on a knife?
Click to expand...


Heating the blade up in a fire will do it to some blades depending on the quality of the knife.

No, boiling water won't do it.
 
Depends on steel and heat treat.
High-speed steel are tempered at 500°C - 600°C, according to Bohler, N690 can be tempered as low as 100°C. Other steels are somewhere between. Boiling water doesn't have 100°C, so IMO it's safe.
 
cali said:
Depends on steel and heat treat.
High-speed steel are tempered at 500°C - 600°C, according to Bohler, N690 can be tempered as low as 100°C. Other steels are somewhere between. Boiling water doesn't have 100°C, so IMO it's safe.
Click to expand...

What physics class did you go to? The boiling point of water IS 100°.

But a quick dip in and out wouldn't ruin the temper. Only if left in there for a long time and completely heatung up the knife blade to that temperature.
 
FWIW, if I remember correctly, when you get to around 200degree celcius the blade starts going a straw yellow colour and you've affected the temper on the surface of the blade(assuming you don't leave the blade at 200degree for a long time....). When you get to a dark blue colour, the heat will go through a large area and affect the temper, this is just for when working with power tools though(like a belt sander when grinding).

Boiling water will not affect the temper of any knife steel.
 
Typical tempering temperatures start at 400 F [200 C ] and may be as much as 1000 F [ 540 C ]..Boiling water is well below tempering temperature .
 
Sorry... it should be "temperature of boiling water doesn't exceed 100°C" :P:P:P
 
Thank you for all the replies!

As a followup question, would it be safe to say that a dishwasher won't ruin the temper on a knife; or in particular — kitchen knives..?

Sorry for all the questions...
 
I'm guessing the reason a dishwasher would ruin the edges is if the knives where banging against eachother or other objects. I've got a Miele with a large horizontal tray on the top, where one simply lays down the cutlery in an organized fashion: i.e., the blades won't touch eachother.

The question was in regard to the temper. So, does dishwashing your blades ruin the temper? I mean, I know that it is dangerous to have knives stickin' up in the dishwasher and that the tensides can cause rust n' all that; but I'm mostly concerned with the temper at this point.
 
I don't have a dishwasher but whatever detergent is being used must be pretty abrasive. I've seen dishes with baked on goop come out sparkling clean. That just can't be good for a knife edge :(
 
Thank you guys! I just wanted to know, cause sometimes it's easier to just toss them in the dishwasher, although it's not such a good idea. I try not to, but it happens... : (
 
General rule of thumb:
You won't ruin the temper of your knife blade unless you heat it to a point where it changes color.

Please don't worry about it; unless you leave it in the oven, or sitting on your stove burner, or in a fire, or in a kiln, you'll be fine.

Also, there are MANY good reasons why you should NOT put your kitchen knives into the dishwasher.
 
stoffi said:
Hi,

I'm wondering how the temper on a knife is ruined.
Click to expand...

Probably more than any other way, the tempering on a knife gets ruined by trying to sharpen the blade on a grinder. You can very quickly heat a thin edge cherry red with a grinding wheel. No one who is inexperianced with sharpening on a grinder should use a grinding wheel to sharpen their blades.

Bill
 
Boiling a knife over time will alter the temper of a knife. I sharpen knives for my daily living among other chores here in my knifeshop and in doing so I've seen that over the course of years of dishwashings knives get softer and grind like made of aluminum.
 
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