Belt sander and change of temper

[awestib]

I am not sure whether this has been discussed before but do we have any tests available that confidentially confirms that using a (regular fast going) hobby belt sander is not changing the temper of the very apex of an edge even is the user cools the blade often enough with dipping it in water for instance?
Why else is there such a concern about using water cooled revolving stones or very slow going sanders (which I wish to have one day)?

Suggestions or opinions greatly appreciated!

 

[fast14riot]

It has been tested before, I don't have a link or citation handy, but it you get the steel to change color, you have likely ruined the temper. Think about the thickness of the edge, sure it heats up quick, but there is lots more steel behind it to absorb the heat. Once that has absorbed the heat then it starts heating up more and then you get discoloration. Conversly, being that thin it doesn't hold onto the heat as much as the thicker steel behind it.

Slower tool, grinders, and watercooled will allow you more time in contact to accomplish the task. Power tools just make mistakes happen much quicker!

-Xander

 

[Brisket]

I was concerned about this when I first got a HF 1x30 (3400rpm) belt sander years ago and took a beater knife and deliberately tried to destroy the temper on it to see how much grinding it took to get there. It was not a scientific experiment, mind you, but it gave me comfort that my normal sharpening routine, including occasional re-profiling was not endangering my precious blades. As fast14riot mentioned, time is a factor and it doesn't take long to sharpen on a belt sander/grinder when using the appropriate belts. Step up your belts when sharpening rather than spending a lot of time grinding on a finer grit belt to get the job done when you should have started out with a lower grit and you should be fine. Quench if you are doing major re-profiling, but I have not found it necessary to do so with maintenance sharpening. I do most of my sharpening on a 1x42 at half the speed (1800) now but i still use the HF and never accidentally destroyed a knife's temper.

 

[Czechmate]

It has been tested before, I don't have a link or citation handy, but it you get the steel to change color, you have likely ruined the temper. Think about the thickness of the edge, sure it heats up quick, but there is lots more steel behind it to absorb the heat. Once that has absorbed the heat then it starts heating up more and then you get discoloration. Conversly, being that thin it doesn't hold onto the heat as much as the thicker steel behind it.

Slower tool, grinders, and watercooled will allow you more time in contact to accomplish the task. Power tools just make mistakes happen much quicker!

-Xander

Good post Xander!

I find on my paper wheels it's easy to heat up blades so now really try and watch my dwell time and pressure so no knives get trashed. I also think doing it this way is a bit safer... Turned the speed down a bit too just to be prudent; I still get great results!