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+--- Thread: Salutations to Stone Sharpeners! (/showthread.php?tid=217)
RE: Salutations to Stone Sharpeners! - me2 - 12-28-2017
It's not a trivial subject. I mentioned before that GE is concerned about grain growth in nickel alloys during grinding. Grain growth in steels isn't really a problem until you get over 1600 F and spend some time there. I would guess high temperature nickel alloys are even higher.
I have seen microhardness tests that show softening during power sharpening of about 5 points. This is of the edge, not the whole blade. That was also on a simple carbon steel, the easiest to soften. Had I been using those knives for less strenuous activity, I might not have noticed.
I look at it with this in mind. Knife makers and manufacturers spend a lot of time and money on their heat treating processes. I've heard of individual makers adjusting tempering temperatures in 25 degree increments to get their desired result. It is irksome to me that there is that much effort put into it, but final sharpening possibly exposes the steel to a huge range of temperatures.
RE: Salutations to Stone Sharpeners! - EOU - 12-30-2017
This thread gets a "top five" nomination for the year in our opinion because its just so damn smart. Smart and open minded people reexamining the very basics of their art. We think that this examination of edge sharpening temperatures is really important and perhaps more important than we realize. There is little doubt that something is going on with steel edges during the sharpening process and some of the general fact and theory discussed here support that. We just don't know yet how it may apply, specifically, to cutting edges and to what degree. Does this have effect with only some sharpening techniques or all? Does it manifest with only some steels or all and to what degree? There will be only one way to get to the bottom of this and that is through experimentation and careful testing. Then we'll find out if it is something or nothing or something in between something and nothing.
Every once in a while, in every scientific pursuit and art form, something comes along that makes people reconsider commonly accepted process and procedure. This could be one of those times and thank you to the participants of this thread for making that a possibility.
RE: Salutations to Stone Sharpeners! - scott.livesey - 12-30-2017
As a maker, I try to use every 'trick' available to prevent heating the blade after heat treat. low belt or disk speed, wet belts, dipping the blade in water after each pass, using fresh belts, less force of blade to belt or disk. It took time to come up with my HT recipes that match steel and my furnaces. heat treating a high carbon steel blade takes about 3 hours plus an hour for furnace to warm up. I usually do batches of 5 to 10 blades at a time, so heat treating 10 blades will take 6 hours. all that time and care is wasted if I over heat the edge. I cringe when I see some of the U-tube videos of commercial makers finishing blades and streams of sparks fly from the edges.
RE: Salutations to Stone Sharpeners! - grepper - 12-30-2017
What I have been trying to find out is if light pressure sharpening on my Kally causes any real world "damage" to the blade. I never overheat a blade. Most of the time there is hardly any perceptible background heating at all. Never any sparks!
I'm open to the idea that the on the micro level at the very edge there might be heating, but what does that really mean for gentle sharpening?
Any heating that is generated, at least the way I sharpen, is minimal and short lived.
Considering the temps/time necessary for HT and tempering are far greater than anything that happens when I sharpen a blade, can it rally make a perceptible difference to the blade? If there is some heating at the very edge of the apex, how deep into the blade is affected? Just my gut feeling is that any change to the blade is pretty minimal and mostly surface related.
When the adverse ramification of grinding is discussed, what does this mean? High speed/pressure grinding? Lots of heat? How does this relate to sharpening?
At least we are raising some interesting questions for discussion and testing.
RE: Salutations to Stone Sharpeners! - grepper - 12-31-2017
Mr. Me2 – Because I sharpen on a Kally, I found a statement you made in post #31 of this thread interesting. You stated, “I have seen microhardness tests that show softening during power sharpening of about 5 points.”
What are “points”? Are you speaking or Rockwell C?
Can you point me to those studies?
RE: Salutations to Stone Sharpeners! - me2 - 12-31-2017
I don't know where it was, but it was a single page test, I believe it was of a sheep shearing blade sharpened on a belt grinder. I don't know the belt speed, but the grit was forget coarse, 120 or 80 so.
RE: Salutations to Stone Sharpeners! - Rupert Lucius - 12-31-2017
Mr. Me 2
Having access to a Starrett C hardness tester 3 houses down the street any time day or night - seldom use it due the fact that for me it is just impossible to get the tapered knife blade aligned and steady for accurate results.
Usually use my Fowler C hardness files (5 ranges) they are much less expensive than an actual Rockwell C hardness tester, and accurate enough for most knife/machine shop needs. They are Japanese made. Use the tip to scratch or dig in to the metal piece in question. If it scratches or just digs in then your metal piece is softer on the Rockwell C scale. Move to the next lower probe until it does not scratch or dig in on your metal piece in question. You have now bracketed the hardness to within a 5 unit range on the Rockwell C scale. The whole process takes only seconds per test range. Recommend when tempering steel to a desired hardness, or when trying to identify the type and hardness of unlabeled scrap pieces.
Grizzly and or MSC sell sets of hardness tester files that work well for spot checking hardness. How about McMaster Carr?
To everyone a Happy, Healthy, Prosperous 2018.
Rupert
RE: Salutations to Stone Sharpeners! - me2 - 01-01-2018
I found the link for the overheated shears, but it's broken.
RE: Salutations to Stone Sharpeners! - Mark Reich - 01-01-2018
Gentlemen, I've spent an Enormous amount of time on this thread, reading, researching, pondering, writing and rewriting and rewriting and... I've found there are many posts or parts of posts in this thread that need to be rectified, clarified, edited or omitted.
First of all, we need a firm understanding that there is Way more disinformation than proper information, Relevant To This Forum, to be found bandied about on the internet. Look hard enough, and I'm sure you may be able to find something as erroneous as "the ability to create 3600°F temperatures dry honing a straight razor". I don't care if you can find 2000 metallurgists to agree on it. I want to see One of them touch a 3600° Anything.
I don't have time or patience for Any more distorted or extreme theories, or irrelevant statements. As we Know, industrial applications may be totally contradictory to our reality. That comes straight from our Fearless Leader's written words, and it is My Job to make sure we stay grounded to Applicable Facts. Grinding heats of 1600°F may be possible. If that takes destruction of a TW-90 to accomplish, it is Not Applicable Here.
Use your Best judgement. One piece of disinformation can cause a totally different reality to set in. We all need to be very careful that we aren't polluting the Truth and Relevance of this Forum. If an enormous conglomerate such as GE is measuring grain growth during grinding, it's interesting. Keep It In Context. Insistently alluding "This could happen to you" is incredibly irksome.
As I said, there are many statements in this thread that won't pass my BSometer. If anyone thinks their previous statements have clouded our reality, you may want to Honorably edit them or retract them. Otherwise I Will. If you find that your post has been edited, and you have a problem with that, you are more than welcome to PM me, Mark Reich, the Administrator, or EOU.
To Be Perfectly Clear - Do Not Try to insinuate that Mr Grepper needs to consider overheating Anything. Ever. It's horribly insulting to those of us who have sharpened thousands upon thousands of blades without coming close to softening a single edge.
RE: Salutations to Stone Sharpeners! - pjwoolw - 01-02-2018
Good post Mark!