09-30-2018, 12:42 AM
(This post was last modified: 09-30-2018, 12:44 AM by KnifeGrinders.)
A few quotes by Cliff Stamp talking on the overheating on the Spyderco forum.
"This is a common misconception, that if the edge itself (the full bevel) does not discolour then you are fine. But again we are talking about the actual cutting edge which is less than half a thousandth of a mm wide. This will over heat immediately on power abrasives."
"It is a common misconception that as long as you hold the blade with your hands, and cool it frequently you can avoid over heating the edge - this is false. The very edge is extremely thin, less than half a micron, it overheats instantly on a belt sander or any other powered abrasive which runs at a high RPM...
The over heating is just on the edge itself, not the actual bevel as the bevel will heat sink into the main body of the blade."
"What is even worse is that the common "solution" is to water dip the edges and thus you are seeing steels which should never be water cooled being done so and thus you are going to get quench cracking...
As soon as it exceeds the tempering temperature it will start to soften the steel, this can be as low as 325 F. The second problem is that the constant subjection to over heating and quenching in water is very violent on the edge even if the steel is suited to those temperatures (high speed steel for example will not suffer temper drawn but will suffer quench cracking)..."
" This isn't an opinion or conjecture, this is materials data, which has been verified and published in the literature. However it also has to be noted that we are simply talking about optimal performance, it isn't like if you sharpen the knife on a belt sander it explodes when you cut a piece of cardboard, it simply doesn't have the same level of edge holding/stability/durability as when you sharpen by hand, ideally with a coolant (water stones)...
Of course you can just use water cooling systems (Tormek)."
"This is a common misconception, that if the edge itself (the full bevel) does not discolour then you are fine. But again we are talking about the actual cutting edge which is less than half a thousandth of a mm wide. This will over heat immediately on power abrasives."
"It is a common misconception that as long as you hold the blade with your hands, and cool it frequently you can avoid over heating the edge - this is false. The very edge is extremely thin, less than half a micron, it overheats instantly on a belt sander or any other powered abrasive which runs at a high RPM...
The over heating is just on the edge itself, not the actual bevel as the bevel will heat sink into the main body of the blade."
"What is even worse is that the common "solution" is to water dip the edges and thus you are seeing steels which should never be water cooled being done so and thus you are going to get quench cracking...
As soon as it exceeds the tempering temperature it will start to soften the steel, this can be as low as 325 F. The second problem is that the constant subjection to over heating and quenching in water is very violent on the edge even if the steel is suited to those temperatures (high speed steel for example will not suffer temper drawn but will suffer quench cracking)..."
" This isn't an opinion or conjecture, this is materials data, which has been verified and published in the literature. However it also has to be noted that we are simply talking about optimal performance, it isn't like if you sharpen the knife on a belt sander it explodes when you cut a piece of cardboard, it simply doesn't have the same level of edge holding/stability/durability as when you sharpen by hand, ideally with a coolant (water stones)...
Of course you can just use water cooling systems (Tormek)."
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