# How do knives get dull?

**URL:** <https://boards.straightdope.com/t/how-do-knives-get-dull/531155>\
**Category:** Factual Questions\
**Created:** [March 3, 2010, 5:47pm UTC](https://boards.straightdope.com/t/how-do-knives-get-dull/531155 "2010-03-03T17:47:01Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![old\_joe](https://avatars.discourse-cdn.com/v4/letter/o/58956e/32.png) [@old\_joe](https://boards.straightdope.com/u/old_joe)\
**Post date:** [March 7, 2010, 5:23pm UTC](https://boards.straightdope.com/t/how-do-knives-get-dull/531155/21 "2010-03-07T17:23:46Z")

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> [@dracoi](#):
>
> When you say you sharpen that frequently, are you talking about using a sharpening steel, or are you using a whetstone or grinding wheel?  
> Partly, it might be a matter of getting used to it. My wife is very particular about how she wants to have her really good knives sharpened… but she refuses to actually get it done. Our 12" chef’s knife has gone at least 12 years and is now so dull that it won’t cut a tomato’s skin.

A steel doesn’t sharpen a knife it just aligns the edge so when i sharpen I use a lansky type kit. When I do sharpen my Japanese vege knife (it is a chisel type blade) the one side is flat and the other is sharpened to a 17 degree angle. I can hold that knife with 2 fingertips and it will slice a ripe tomato with only the weight of the blade. I dont sharpen all that often, it might be several months. I do think that its what you get used too, I have known many pro chefs once they seen a really sharp knife never go back.  
I worked summers in restaurants and the chefs knives there were never very sharp. A chef is not taught anything about knives, they concentrate on the food end. Oh, btw, never ever use a powered wheel to “grind” a blade, it is very easy to heat the blade enough to change the temper and then you are snookered.

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**Author:** ![old\_joe](https://avatars.discourse-cdn.com/v4/letter/o/58956e/32.png) [@old\_joe](https://boards.straightdope.com/u/old_joe)\
**Post date:** [March 7, 2010, 5:36pm UTC](https://boards.straightdope.com/t/how-do-knives-get-dull/531155/22 "2010-03-07T17:36:25Z")

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> [@DSeid](#):
>
> It’s been explained to me like this (In a cooking “knife skills” class) -
> 
> The edge of a well sharpened knife is very thin and ends up having little “teeth” to it no matter how hard the metal. Every time you use the knife you bend some of those irregularities one way and the other. Having those teeth randomly aligned makes the knife function less well and a steel - used after each job - keeps those “teeth” all lined up in the middle, more or less..

very good analogy. Some water stones can be as high as 8000 grit. Since the sandpaper you probably have in the garage is like to be 120 you can see this is pretty fine. They actually feel very very smooth. Even using this stone though the edge, under magnification, is as as you say quite jagged. Since a steel doesnt sharpen but rather aligns, eventually you need to sharpen the knife. The longer you leave it the more work you have to get the proper bevel again. A hunting knife might be 20 or 22 degrees while a straight razor would be more like 12 degrees.

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