A very quick and close look at 'steeling'

Excellent. If nothing else, you've inspired me to go back and read the sections on transformation toughening in my ceramics book. Those books were both published since I finished school, so I haven't read them. I'll see if I can get one at the local library though. There are a couple of sections in my book of how to toughen ceramics, complete with micrographs of the propogating crack and the transformation field in front of it. The mixture I heard about used alumina instead of yttria, but just skimming this section also mentions magnesia and a couple others. Yttria must be more effective, or have some other advantage.
 
I don't know if yttria is particulary good or not. It's just what I have heard about most often! So don't read too deeply into that bit. :)

Sincerely,
--Lagrangian
 
me2 said:
There are a couple of sections in my book of how to toughen ceramics, complete with micrographs of the propogating crack and the transformation field in front of it.
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Hi me2,

Could you post one or two of the micrographs from your textbook? I would love to see a picture of transformation toughened zirconium which shows the propagating crack and the transformation field in front of it. :)

Sincerely,
--Lagrangian
 
Its barely visible in the micrograph. I dont think it would be visible at all in a scan.
 
Here's the update to the update. Redid the Aus8, Carbon steel, and Sandvic on the edge of my newer Pyrex (not borosilicate, but soda-lime glass).

I thought this would be very interesting as I can see how it went to work on these edges and I still have pics from their last test.

Here's the Aus8 - not a lot of visual difference - you can see where the steel appears to be piled up a bit as it comes off the worked apex and back down to the stone-ground region. A further improvement in fine cutting - this knife and the others I did this too could all whittle a hair with just a little draw along the edge - this knife in fact split the hair in half the instant it caught. Pretty good for two quick steps removed from a combination silicon carbide stone. Entirely possible the steeling step could be eliminated and then you're going straight to the glass from a fairly rough stone and splitting hairs....

Aus8_Glass_640.jpg~original


Here's the carbon steel edge - seems to have undergone an improvement in apex "cleanliness" - a bit less irregular and cuts a bit better as well. Evidence of the metal being worked is not as apparent - there are fewer irregularities to be smeared.

CS_Glass_640.jpg~original


Now for the Sandvic. Much like the Aus8, not a lot of visual change, but an improvement in fine cutting based on hair splitting.

EKA_Glass_640.jpg~original


I guess the next step might be to try going from a freshly ground edge straight to a glass rod, but I think I really am done with this topic for a little while. Based on my results I'd be very surprised if the glass were incapable of pushing/burnishing the irregularities along the apex into a much more refined edge, much as the steel did. In any event, the glass had to have done so already to improve on the unused/unworn steeled edge, just a question of what its capable of doing on its own.
 
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Ive been sharpening for 30+ yrs and I feel like a complete novice and idiot after reading this thread.. As Spock said "facinating"
 
Late to the party here, but this is great info. Im diggin into past metallurgy classes from my days in materials science and mechanical engineering.

Yes, "burnishing" is useful for forming an edge. Look up cabinet scrapers, I have some and they routinely peel paper thing shavings off of hardwood even cross-grain... I use a carbide "burnsiher" to form the edge that does this. And this is basically what smooth steeling does to the knife edge.

At the edge of a fine piece of steel when run across a round/cylindrical object the theoretical contact area is a line or a point (if there is no deformation) which means that contact pressure is nearing infinity... :D ...Reality is different of course but its still VERY high contact pressures, which exceeds the strength of the metal in that small area and causes plastic deformation of the steel at the edge... Deforming the metal matix work hardens it by using up the available dislocation points in the metal crystal matrix, each working uses up more until they are all gone, then you have brittle failures.

Localized heating is also a problem, especially with powered edge tools like grinders etc, softening the edge, and the heat transfer is a function of the volume of the metal and the "contact" area of the edge with the rest of the blade. In other words it very easy to drive the temperature up in the fine edge. Depending on the steel grade/chemistry and the temperatures invovled and rate of cooling this can make the edge harder or softer.
 
I also came across this when looking into some natural stones for scythe honing that another member posted about. I had no idea these tools were sharpened by peening and then a light job with a honing stone. With the right jig or hammer/anvil you could probably do a good job on a machete or other large chopper. I have no idea what the RC is on a scythe. There's always more out there to learn.

http://scythesupply.com/workshops/peeningWorkshop.htm
Anvil_handshot2.jpg
 
Hi Rapt_up,

Thanks for your post! :) It's good to hear from someone with a real technical background in engineering and material science.

Sincerely,
--Lagrangian
 
Once again a thank you to HeavyHanded for those fantastic and informative photos. It is plain for anyone to see that steeling does a lot more to a blade than simply straighten out the edge. Aside from metallurgical science, of which I know very little, pure logic borrowed from geologists will tell us a similar story. For a century or more they have been working with the so-called Mohs hardness scale, based on the fact that a harder mineral will scratch a softer one. Geologists in the field usually have a small rectangle of window glass in their pockets, which weighs in at about 5.5 on the hardness scale (talc=1, diamond=10). If they find a mineral they can't recognize, they try to scratch the glass with it, or vice versa, in order to narrow down what it might be. The carbon steel used in making a sharpening steel is harder than stainless steel used in kitchen knives, and if the latter is scraped along the former, the former is going to leave some kind of a trace. The harder (carborundum and ceramic=9 or thereabouts) and more abrasive the material, the more it will leave a mark. One steel that is slightly harder than the next will remove some material from the softer one. Not much, but enough to make a difference.

One more thing before signing off, an observation I made (again) this past week. My stainless steel kitchen knives were beginning to stain ever so slightly from all the work they do. I got out the steel polish (related to what I use on my strop) and polished up the sides of the blades till they looked just like new. Wow, that a difference that made when slicing tomatoes etc! It brought home once again the knowledge that had been on vacation for a while that the blade that follows the edge through whatever you're slicing can cause a lot of drag. The more highly polished that is, the more it will assist the sharp edge in making kitchen work less of a chore.

Sam
 
Are all kinds of things that fall into this hobby. After observing Kydex scratching satin polished steel, but not brightly polished steel, it makes one wonder a lot more about plastic deformation etc. Even in my test with the steeling, the steel takes all manner of abuse as well as working the knife edge. What was most interesting is the direction of the scratches in the surface treatment on the 'steel' made a big difference in how it burnished. I also noticed over time (and have seen a similar effect on my Washboard edges when burnished/polished with plain paper) that steeling/burnishing has the most notable improvement on an edge that has been freshly ground and has high and low points - makes it a lot easier for the 'steel' to flow the metal into a finer edge. Once its been flattened out a few times it becomes a lot tougher to form a truly acute cutting edge with this method.

Was very fun to do this one - of all my short "photo essays", this and the '$6 carbide scraper' are the ones that were most informative to me.

Martin
 
After all this Martin, what is the best steel in your opinion? It seems a "regular" smooth (not grooved) knife steel?
 
awestib said:
After all this Martin, what is the best steel in your opinion? It seems a "regular" smooth (not grooved) knife steel?
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It should look "smooth" to the unaided eye, but have very fine microscratches running lengthwise - maybe in the 1500-2000 grit range.

For softer steels you can use a heavy grooved steel like a file, and follow up with the finer 'steel' to put on the finishing edge.
 
David Martin said:
Thanks HH, for this information into a look at steeling and what it does to an edge. So, just a few light strokes, not the numerous pounding I observe most meat cutters doing. This helps to maintain the edge not hurting it as some put forth. DM
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A bit late to this party but here goes. I was a meat cutter for fifteen years in a Packing House. After sharpening with a Norton India Stone, all that was necessary to keep a good edge was a few swipes on my homemade steel made from a rat tail file. This steel was very fine - smoothed with 400 grit emory cloth. Then magnetized. The knives used were Russell Boning Knives so probably medium quality steel.
 
My hat is off to you ^ as I know you guys Really work in those places and under harsh conditions. Did you use a edge leading stroke or edge trailing when steeling? I like the shape of a Russell 6" boning knife. I would say the hardness of that knife is like 55-56 rc. DM
 
Heavy Handed,

I thought that I was the only person on this forum that was nutty enough to use "dry,shaving of facial hair" as a test of sharpness.:p

It's good to know there is a kindred spirit here!:D:):D
 
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