MadSci Network: Engineering

Re: Why do razor blades go blunt?

Date: Fri Apr 27 11:37:20 2001
Posted By: Nauzad Tantra, Undergraduate, Production/ Industrial engg., D J Sanghvi college of engg.
Area of science: Engineering
ID: 987033277.Eg

Hi Nicola,
In a word, the answer to you question is "wear".

Every material has its own hardness. Tungsten steel, as you have rightly 
pointed out, is quite tough and hard. Hair, in comparison is softer. 

However, over a period of time, even hair is able to form microsopic 
scratches on the steel and cause it to lose its sharpness. No matter how 
large the differance between hardness of any two materials, the harder one 
will eventually wear out. However, the greater the differance in the 
hardness, the longer the harder material lasts before it wears out.

This is applicable not only to hair and steel, its applicable in most of 
the things you see around you. Carpenters sharpen their tools made of Tool 
steel even though they use it to cut wood (much softer). Kitchen knives 
are used to cut vegetables and meats.

Thus, no matter how large the differances in hardness, eventually the 
harder material will wear out. 

Hope I've cleared your doubt. If not, feel free to contact me.


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