10-17-2018, 06:31 PM
Great post. Thanks for the effort and sharing EOU. Your micro images seem to be improving a bit.
These results don’t surprise me as I’ve never noticed much of any heating of the blade when I sharpen. That said, I do have a very light touch when sharpening. I'm open to the idea that heating occurs, but the evidence now seems to indicate that it probably is not a problem.
In eager anticipation of this test I posted in the Knife Making and Bladesmithing forum questions about the time and temperature required for tempering. I was curious because I thought it possible that the edge could possibly warm into tempering range. However, I reasoned that when judiciously sharpening, even if the blade did manage to reach tempering temperature, it does so for a very ephemeral period of time and would not hold temperature long enough to change the temper of the edge. Regardless, so far, the Tempilaq tests apparently indicate that temps are not reaching even the lower end of tempering range, and I postulate that even if it did reach tempering temperature, the short duration of those temps would render the effect on the blade insignificant.
Obviously enough pressure was applied between blade and belt to create a burr so we know that a blade can be sharpened on the Kally without significant heating.
I did some ferreting around and found some non-scientific observations stating that when applied to thin surfaces, specifically brass cartridge casings, that Tempilaq may be a little slow to trigger resulting in the material the Tempilaq is applied to may be at a slightly higher temperature than the Tempilaq indicates. Care must be taken in understanding what is being said as the Tempilaq was applied to the inside surface and heated from the outside. Part of what is being discussed is thermal migration through the brass and not specifically how fast the Tempilaq reacts once the surface that Tempilaq ia applied to reaches trigger temperature:
http://www.65guys.com/cartridge-case-ann...equipment/
Here is some additional information regarding the properties of cartridge brass. This reference shows the annealing temperature to be between 800-1400 degrees F. If that’s the case, why is 750 degree Tempilaq recommended? We spoke with one of the annealing machine manufacturers and they explained that the reaction time of a temperature measurement system will be slower than actual temperatures achieved for something as thin as a case neck. As a result, the indicated temperature will be exceeded.
http://forum.snipershide.com/threads/6mm...ble.61253/
“Now, brass isn't a perfect conductor, it takes time for it to heat up and for the grain structure to change once it does, but this still probably has a lot less of a lag to it than the time it takes for the heat to transfer to the Tempilaq and melt, which is much less thermally conductive than the brass. So, if you're using 750 F Tempilaq inside of the neck, the brass has probably exceeded 800 F when its only started to melt and has shot quite a ways past it when its fully melted. I saw this. If I put 750 F Tempilaq and 850 F Tempilaq in the same neck, it was not possible to get the 750 F Tempilaq to fully melt or even partially melt without the 850 F Tempilaq starting to melt. 800 F Tempilaq surely would have melted to some point in between. Parts of the brass itself were likely over 900 F. I could totally melt the 850 F Tempilaq without fully annealing the brass. I have to go a bit longer to succesfully do it.”
Even taking the above into consideration, I would still postulate that if parts of the blade were indeed slightly hotter than 325° it would not be excessively so, and the period of heating so short as to be of little significance. Furthermore, this experiment clearly indicates that the test blade did not get anywhere even close to annealing temperatures let alone tempering temperatures.
These results don’t surprise me as I’ve never noticed much of any heating of the blade when I sharpen. That said, I do have a very light touch when sharpening. I'm open to the idea that heating occurs, but the evidence now seems to indicate that it probably is not a problem.
In eager anticipation of this test I posted in the Knife Making and Bladesmithing forum questions about the time and temperature required for tempering. I was curious because I thought it possible that the edge could possibly warm into tempering range. However, I reasoned that when judiciously sharpening, even if the blade did manage to reach tempering temperature, it does so for a very ephemeral period of time and would not hold temperature long enough to change the temper of the edge. Regardless, so far, the Tempilaq tests apparently indicate that temps are not reaching even the lower end of tempering range, and I postulate that even if it did reach tempering temperature, the short duration of those temps would render the effect on the blade insignificant.
Obviously enough pressure was applied between blade and belt to create a burr so we know that a blade can be sharpened on the Kally without significant heating.
I did some ferreting around and found some non-scientific observations stating that when applied to thin surfaces, specifically brass cartridge casings, that Tempilaq may be a little slow to trigger resulting in the material the Tempilaq is applied to may be at a slightly higher temperature than the Tempilaq indicates. Care must be taken in understanding what is being said as the Tempilaq was applied to the inside surface and heated from the outside. Part of what is being discussed is thermal migration through the brass and not specifically how fast the Tempilaq reacts once the surface that Tempilaq ia applied to reaches trigger temperature:
http://www.65guys.com/cartridge-case-ann...equipment/
Here is some additional information regarding the properties of cartridge brass. This reference shows the annealing temperature to be between 800-1400 degrees F. If that’s the case, why is 750 degree Tempilaq recommended? We spoke with one of the annealing machine manufacturers and they explained that the reaction time of a temperature measurement system will be slower than actual temperatures achieved for something as thin as a case neck. As a result, the indicated temperature will be exceeded.
http://forum.snipershide.com/threads/6mm...ble.61253/
“Now, brass isn't a perfect conductor, it takes time for it to heat up and for the grain structure to change once it does, but this still probably has a lot less of a lag to it than the time it takes for the heat to transfer to the Tempilaq and melt, which is much less thermally conductive than the brass. So, if you're using 750 F Tempilaq inside of the neck, the brass has probably exceeded 800 F when its only started to melt and has shot quite a ways past it when its fully melted. I saw this. If I put 750 F Tempilaq and 850 F Tempilaq in the same neck, it was not possible to get the 750 F Tempilaq to fully melt or even partially melt without the 850 F Tempilaq starting to melt. 800 F Tempilaq surely would have melted to some point in between. Parts of the brass itself were likely over 900 F. I could totally melt the 850 F Tempilaq without fully annealing the brass. I have to go a bit longer to succesfully do it.”
Even taking the above into consideration, I would still postulate that if parts of the blade were indeed slightly hotter than 325° it would not be excessively so, and the period of heating so short as to be of little significance. Furthermore, this experiment clearly indicates that the test blade did not get anywhere even close to annealing temperatures let alone tempering temperatures.
