A very quick and close look at 'steeling'

Hi bluntcut,

Thanks! I think I understand what you're saying now, and I think I agree. This where a picture is literally worth a thousand words (or at least a few hundred!). :)

bluntcut said:
According to the definition of work-hardening - you're right. :saturn:I was thinking more in line of tempering where steel lattice configuration changes rather than inter-lattice or grain level deformation. For example: cpm-m4 become harder with temperature going up (to certain point before softening occurs).
Click to expand...

Actually, you may be surprised (I certainly was). Here's a thread about "Unwanted Tempering Whilst Sharpening." The main posts in this thread, are by the metallurgist Roman Landes who wrote a book about metallurgy and knife performance. Most unfortunately, the book is written in German, with no plans for an English edition. Some knife enthusiasts, as Cliff Stamp, have read Landes' book (I guess he knows German?).
http://www.hypefreeblades.com/forum/viewtopic.php?f=3&t=391

The basic points that are made in that thread:
(1) Grinding generates heat, a lot of heat. This can be measured by placing temperature sensors in a workpiece and then literally grinding all the way to the sensor.
(2) Heat generated by grinding flows from the surface into the main bulk of the metal.
(3) The knife edge itself is very very thin; heat generated near the knife edge has almost no where to go, and so can become concentrated. This can raise the temperature of the edge a lot. Apparently, enough to cause unwanted tempering of the steel in a tiny area that includes the very edge of the knife.

Personally, I found this very surprising, even as a physics major who has had to do homework problems on the heat equation. I wish that thread in www.hypefreeblades.com had continued the discussion, especially with Roman Landes' commentary, but the thread is rather short. Landes does point to books and research papers about this, but they are all in German, which makes them too difficult for me to read (I know virtually zero German). :(

If any of you know German, and are technically inclined, then we would just love it if you could read some of the references and report back to us.

Short of that, I'm hoping to read some textbooks (in English) on abrasive machining, tribology, polishing, metallurgy and cutting. But that is a ton of material.... I won't be able to report back on that anytime soon; at least I don't think I will be able to. :rolleyes:

Metallurgy has not only been studied, it has been studied intensively for centuries (by blacksmiths and scientists). In the modern era, literally billions of dollars of advanced research have been applied to understanding metals. If you're an amateur (like me), it is okay to ignore all that for fun, and just say,"Hey, I'm doing my own research/experiments for my own amusement!" I do this a lot; mess around with stuff for my own amusement, and ignore whether nor not I'm doing actual new research; if it is fun and interesting to me, personally, that is all that really matters. This is perfectly fine and wonderful! :)

But if you are more serious, if you are willing to put hours and hours of work into trying to do scientific sharpening tests, and are using advanced equipment (such as high-powered microscopes), and have spent many man hours thinking about what actually happens at a knife edge, well... to you (and to myself) I would say:

It is a good to stand on the shoulders of giants.

Sincerely,
--Lagrangian

P.S. Someone please give me a pile of money, so I can get on a plane and fly to whatever country metallurgist Roman Landes is in, and get him to have lunch and dinner with me. Just kidding... :) But darn it, I wish we had a real metallurgist to talk to. Landes will sometimes post the forums, but not that often. I don't know, but I imagine he finds it too tiring to communicate with all the fan-boy types.

P.P.S. Here is a list of technical and semi-technical resources. I can't recommend many of them, because I have not read them, but here are specific books I'm interested in:

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General Material Science at the level of popular science:

_Why Things Break_ by Mark Eberhart (2003)
http://www.amazon.com/Why-Things-Break-Understanding-World/dp/1400047609
Note: Contains zero math, fun to read. Highly recommended.

_The New Science of Strong Materials_ by J. E. Gordon (2006)
http://www.amazon.com/Science-Materials-through-Princeton-Library/dp/0691125481/ref=pd_sim_sbs_b_1
Note: Slightly dated, but very good. Some high-school math.

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Technical book(s) on Cutting:

_The Science and Engineering of Cutting_ by Tony Atkins (2009)
http://www.amazon.com/The-Science-E...sr_1_sc_1?ie=UTF8&qid=1337470500&sr=8-1-spell
Note: Reading this now. Looks to be at the undergraduate level; seems to mostly use high school math (up through trigonometry and a little calculus).

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Knife Sharpening:

_Experiments on Knife Sharpening_ by John D. Verhoeven (2004)
http://www.mse.iastate.edu/fileadmin/www.mse.iastate.edu/static/files/verhoeven/KnifeShExps.pdf
Note: Free. Almost zero math beyond a couple of angle calculations. A ton of fascinating electron microscope pictures of knife edges.

_The Complete Guide to Sharpening_ by Leonard Lee (1995)
http://www.amazon.com/The-Complete-...=sr_1_1?s=books&ie=UTF8&qid=1337473100&sr=1-1
Note: Not really technical (zero math). From the perspective of a wood-worker; has a chapter on the microscope details of how wood is cut, and the formation of wood chips / wood shavings. Mostly practical information about details of how wood-working tools actually work, and how best to sharpen them. Pretty interesting, but I got tired about 2/3rds of the way in, reading about the nth type of wood tool (chisel, saw, knife, gouge, file, planer, scraper, burnishing the scraper,... etc.), and it's various details. But if you love cutting wood, especially in a wood-shop, definitely check this out. Written by the president of http://www.leevalley.com/ which sells woodworking tools.

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Technical books about grinding, cutting, and polishing of metals:

_Tribology of Abrasive Machining Processes_ by Ioan D. Marinescu (et al.) (2005)
http://www.amazon.com/Tribology-Abr...=sr_1_1?s=books&ie=UTF8&qid=1337470658&sr=1-1
Note: Very expensive. Trying to find this in a library. Looks to be technical at the undergraduate and possibly the graduate level.

_Handbook of Lapping and Polishing_ by Ioan D. Marinescu (et al.) (2006)
http://www.amazon.com/Polishing-Man...=sr_1_1?s=books&ie=UTF8&qid=1337470753&sr=1-1
Note: Probably written at the level as _Tribology of Abrasive Machining Processes_ or higher; looks like a collection of review papers at the research level.

_Handbook of Machining with Grinding Wheels_ by Ioan D. Marinescu (et al.) (2006)
http://www.amazon.com/Machining-Man...=sr_1_2?s=books&ie=UTF8&qid=1337470753&sr=1-2
Note: Probably at a level similar to _Tribology of Abrasive Machining Processes_.

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Metallurgy:

_Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel_ by John D. Verhoeven (2005)
http://www.feine-klingen.de/PDFs/verhoeven.pdf
Note: Free and downloadable!

_Steel Metallurgy for the Non-Metallurgist _ by John D. Verhoeven (2007)
http://www.amazon.com/Steel-Metallurgy-Non-Metallurgist-J-Verhoeven/dp/0871708582/ref=pd_sim_sbs_b_1
Note: Not free, but looks interesting. Seems to be highly recommended by www.HypeFreeBlades.com

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YouTube: (Technical)

Metallurgy Class Lectures on Youtube from the University of Oxford, presented by Professor H. K. D. H. Bhadeshia:
https://www.youtube.com/user/bhadeshia123/videos?view=1

Books associated with Bhadeshia's class, many of which are freely downloadable:
http://www.msm.cam.ac.uk/phase-trans/books.html
Note: These are technical books, some at the undergraduate level, some at the research level. Some are modern research, and some are seminal papers or books in the history of metallurgy.

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YouTube: (For fun and/or only semi-technical (no math)):

Microscope video of cast iron being machined:
https://www.youtube.com/watch?v=XZh6WGR16q0

"Slow motion of what happens in the cut. Different coatings, different materials."
https://www.youtube.com/watch?v=mRuSYQ5Npek&feature=BFa&list=FLles5SBnY2MP8RwytEAsitQ

"This old movie shows a magnified (~100x) moving image of machining steel with a zero lead angle about a +30° rake angle and about 5° relief (clearance) angle and formation of a BUE (Built up edge). It also has a cartoon showing how the BUE formation damages the finished machine surface."
https://www.youtube.com/watch?v=-Tf...DvjVQa1PpcFN8IeIXg9wYBIcVnT4jZO2dRm-KIwpN76w=

And a educational tutorial that simulates grains and dislocations using solder-balls between two glass plates, which are "annealed" by vibrations from an ultrasonic speaker:
https://www.youtube.com/watch?v=oBb...DvjVQa1PpcFN8IeIXg9wYBOxogYKZhfD8e6H3q7hiBUk=

Video of a steel sample undergoing martensite transformation (!!):
https://www.youtube.com/watch?v=OQ5...DvjVQa1PpcFOFwjqw2BNOW4L5b3kOBOvbOtFf5IAkvLE=

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Forging vs. Stock Removal:

_The Lowdown on Forging_ by Kevin R. Cahsen (2004).
http://cashenblades.com/images/articles/lowdown.html

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Hardness and Hardness Testing:

http://www.gordonengland.co.uk/hardness/
Notes: Excellent website about what Rockwell Hardness _really_ is. Also goes over Vickers Hardness, Brinell Hardness, and several other types of hardness scales, and has some tables for approximate conversion between hardness types.

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Deburring:

_Deburring and Edge Finishing Handbook_ by Laroux K Gillespie (1999)
http://www.amazon.com/gp/product/0872635015/ref=ox_sc_act_title_10?ie=UTF8&m=ATVPDKIKX0DER
Note: Gillespie has several other books on machining, finishing, and deburring. I don't know which one is best.
http://www.amazon.com/Hand-Deburring-Increasing-Shop-Productivity/dp/0872636429/ref=ntt_at_ep_dpt_3
http://www.amazon.com/Mass-Finishing-Handbook-LaRoux-Gillespie/dp/0831132574/ref=ntt_at_ep_dpt_4

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HypeFreeBlades.com has a list of books they recommend for learning metallurgy:
http://www.hypefreeblades.com/bib.html
 
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This thread ought to be stickied .. Very good read!

HH,

Stropping fast and slow will result differently due to cold hardening is new to me. Have always been thinking it's abrading the metal with smaller particles (compound).

I guess it will be very difficult to check due to human inability to maintain exact angle when moving fast vs moving slow. That's one of the reason beginner usually is advised to go slowly, and Taiji is also practiced slowly :D to make the movement accurate.

The result might be inaccurate, with the heat factor as well (Lagrangian post on tempering the edge). So many variables, not to mention the most gross of all: whether the edge has been fully apexed before (always my problem :) lol).
 
Lagrangian, now I know where you're getting your information and background. It is, imo, some of the best posted here in recent memory.

Something to keep in mind about steeling. I think that Verhoeven and Jaranich are steeling by holding the steel/rod 90 degrees to the edge and sliding the steel along the edge, where most people I see use a steel by holding it and making swipes/slicing motions along the steel. This will have an effect on what happens at the edge. I have just started some experiments on steeling myself, and will post on it when I'm done.

Something else to remember is effect of the very small cross sections we are dealing with when discussing the edge and it's contact area with a steel. Just as an example, say you use about 0.0625 pounds (1 oz, very light) when steeling. Lets say that gets spread over 10 square microns. This is just an example, but somewhat in the ball park, since very sharp edges are about 1 micron wide or less. The pressure/stress at the contact point is well beyond the strength of any steel I know. Also, even 1095 steel tempered at just 400 degrees F has 1-2 percent ductility. Not very much, but enough that there can be some measurable plastic deformation, especially on the level that microscopes would be able to see.

HH, you REALLY make me want a digital microscope. I have a hand held one that goes to 40x maximum.

The only thing I can say for certain on my own steeling experiments is that on soft steels, it can greatly extend the life of an edge before going back to the stones. This was confirmed on a blade in the low 20's HRc. Once the edge stopped shaving, I was able to bring it back to basically it's original sharpness for about 3-4 more rounds of cardboard slicing. Granted, my hardened blades in the experiment have not been steeled yet, and are still shaving after several rounds of cardboard, but you get the idea. From my experiments, I think steeling is an excellent way to maintain an edge without having to go back to the stones and remove considerably more metal. The condition placed on this statement is that you have to steel in time to do some good. There is a considerable window where steeling will work well, but if you miss it, you have to go back to the stones. For kitchen knives, where steeling is most common, the first time the edge fails to start a cut on the first or second slice across a tomato or such is the time to steel, and lightly. Heavy steeling will make serrated blades out of high hardness kitchen knives and cabinet scrapers with nice burnished burrs out of soft knives. As an illustration, see where Lee recommends burnishing high speed steel lathe scrapers to form a polished hook for turning. This is in The Complete Guide to Sharpening referenced above. These steels have little ductility, but will still form a durable hook for this type of cutting.
 
stoffi said:
Heavyhanded,

I interpret your images not as if the steel has been squashed out, but rather, that the metal has been polished in another direction than the sharpening lines (perpendicular) and with a fine medium (the steel). I don't believe you could actually squash the metal as you're suggesting, since the steel is too hard to deform with such little force and especially since it is supported by the surrounding steel. It's sort of like insisting on squashing out the back of a metal pan by caressing it with another one. However, a burr or rolled edge will definitely align back into place, because there is less supported metal to "grab hold of", or shove around; just as it is easy to bend soft sheet metal around -- but it would be harder to squash it out. You'd need to hammer it hard.
Click to expand...

I should have included a bit more about my test method. While polishing my test steel I removed it from the handle and left it that way. The steel was placed across the block I use for my stones, and the steeling path was nearly identical to my grinding path, not perpendicular. In the pics there is an almost complete lack of what could be called abrasive tracks through the affected areas. 5 passes with a DMT EEF or Spyderco EF wouldn't refine an existing grind pattern from a fine Crystalon stone to that extent, and certainly not without burr formation or abrasive tracks cut into the existing pattern, both of which are absent. If it were an abrasive action, one could use a steel to restore a very dull edge - this is not the case. Combine that with the complete lack of felt friction when running it along the steel and I can only come to one conclusion based on what I can observe - the subsequent refining is a product of plastic deformation/flow and not an abrasive refining action. It is my belief that all refining at the high end recruits a certain amount of plastic flow to accomplish its end, be it stropping, backhoning on a waterstone, running on a borosilicate platter with tincture of green (how microtome blades used to be final finished), etc...

I did attempt to realign a visibly rolled edge on my test knife prior to regrinding the apex and even using a somewhat reckless amount of pressure the roll would not fall back into place. Any realignment must be at a very microscopic level.
 
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I'm in a chatty mood tonight, so I thought I'd offer some more information on steeling, and, since Lagrangian brought it up, toughness.

Material science discusses in different places and under different circumstances three types of toughness.

Impact toughness - this is the one we are familiar with in chopping knives. It is the one measured by the Charpy and Izod impact tests. It measures the amount of energy needed to fracture the rather small sample, a 10mm by 10mm by 50mm (I think) bar, sometimes with a V notch (very tough material), a C-notch (intermediate material), and no notch (relatively brittle material). Most cutlery steels are tested without a notch, but some of the tougher ones use a C-notch. The specimen size is not fixed, and I've done several "reduces section" impact tests on samples that are thinner than the 10mm standard. This is sometimes done for lab tests of field failures when there is not enough material for full section specimens. I changed jobs, so I can't go back and look, but I don't remember a distinct correlation between energy absorbed and specimen size. I can say no reduced specimen ever stopped our Charpy hammer dead in its tracks like some full sized ones would do. It was a 300 ft-lb capacity machine.

Type 2: Tensile Toughness - I'm not sure if this is the proper name, but I'll use it here. It's a measure of the total energy absorbed by a tensile specimen before fracture, some of which is recovered when the load is removed or the specimen breaks, due to elastic stretching (deformation) of the specimen. The energy is calculated by calculating the area under the stress strain curve (force times length). Very ductile samples can absorb tremendous amounts of energy, as long as it is introduced slowly. This is the difference between this type of toughness and impact toughness.

Type 3: Fracture Toughness - This is even less mentioned than type 2. Abreviated Kic in materials texts, it is essentially the sensitivity of a material to the ever present flaws found on the surface and internally. This is where the model of the propogating crack tip is most often mentioned, and one of the causes for the confusion of early engineers that Lagrangian mentioned. Some ceramics have tensile strengths as high as common structural steels, but they cannot be tested using a normal tensile machine. The flaws in the surface and internally will magnify any uneven loading in the machine jaws and just crack the material. A three point contact test was developed for this reason, to provide tensile strengths of very brittle materials with low Kic values. Very high strength steels suffer from the same issues. Ceramics, even the relatively tough ones used in knives, have much lower fracture toughness than steels. Again, this one is concerned with what happens to the energy needed to propogate the crack, and where to put it besides using it for this purpose. Some can get pretty complicated. The zirconia used for ceramic knives is called transformation toughened zirconia. It's composition is in a region of the phase diagram that allows a stress induced transformation to happen at the crack tip. This transformation requires energy, which is no longer available to propogate the crack. This can all get very complicated pretty quickly, and I've not looked at it in detail in many years.
 
HeavyHanded said:
I did attempt to realign a visibly rolled edge on my test knife prior to regrinding the apex and even using a somewhat reckless amount of pressure the roll would not fall back into place. Any realignment must be at a very microscopic level.
Click to expand...

It's possible we could be looking at 2 different effects from what is to us the same action. The effect of steeling a freshly sharpened edge could be quite different from steeling a rolled or dulled edge. The effects could be different depending on grit used before steeling as well. I think Verhoeven noted what appeared to be the bending and plastering of a large burr up against the rest of the edge for one condition or another used in his paper. The effect was a sharper edge than before, entirely based on plastic deformation, like folding a piece of tin foil. I think this was after sharpening with relatively coarse grit, but haven't read that paper in a while.

It took some pretty hard staring, but I can just see the area near the edge that has been smoothed out at a slightly higher angle. Don't rule out adhesive wear between the steel and the edge. I don't have any idea how it might work on such light contact as we're talking about, but it could still be contributing.

I have not verfied this myself, but some users report a decrease in edge holding when knives are steeled several times before stoning. Each time it is steeled, it will need it again sooner than last time, until the edge just won't last, or finally breaks off. HH, have you noticed this on your kitchen knives?

I don't know who mentioned it, but the common steeling technique seen on kitchen videos isn't much more than randomly banging your edge into a steel at angles between 10 and 30 degrees per side.

This is an excellent thread on a very misunderstood topic. No one can say "pics or it didn't happen"

Also, since it was mentioned earlier, I don't think cold working would have a great effect on strength, with only 1-5 percent ductility left in knife steels. It happens I'm sure, but I don't see it strengthening the steel much. It could definately be a mechanism for reshaping the very cutting edge though.

Has anyone tried a nitrided steel rod? These are available from some sources and, once treated, the hardness will be greater than all but the latest super steels (68-72 HRc).
 
Lagrangian said:
Hi bluntcut,
If any of you know German, and are technically inclined, then we would just love it if you could read some of the references and report back to us.
Click to expand...

CALLING SCHMALHAUS!


He is a German that posts knife reviews here and on youtube. PM him if you want to proposition him. His youtube user name is stschmalhaus.
 
I should have included a bit more about my test method. While polishing my test steel I removed it from the handle and left it that way. The steel was placed across the block I use for my stones, and the steeling path was nearly identical to my grinding path, not perpendicular.
Click to expand...
Thank you for adding this..I have to ask at this point..depending on a preferred method, is there really a difference in effect, whether one uses a steel or a strop?
That may be vague, but what I mean is, I am recently learning how to strop, and am greatly appreciating it's value, primarily for maintaing an edge after a proper sharpening..I am at a loss now in seeing a difference in view of a steel; am I incorrect in the understanding that both are used in either the last step of a sharpening, and/or to maintain an edge until the next sharpening..so it all boils down to a preferred method for which we prefer..to strop or to steel?
 
Lively discusions conducive to learning. Operation-research (complex variables heat equation) may consider as work, now throw in experts and complexities could freeze the brain (of mine:emptiness:).

Wondering about strop? mechanically it's quite different than steeling for sure, please read 'stropping: angle plus pressure' sticky above.

Metal plastic-flow != compress != stretch, I see plastic-flow as more of surface displacement mostly along the surface. Bend copper pipe mainly resulted in compress & stretch, harden perhaps due to changed in copper structure energy potential.

btw - an easy to see plastic-flow&compression is to use your blade to gently slice cut the lip of a glass jar, which has about the same size in area of impact for rod vs bevel.
 
Barrabas said:
Thank you for adding this..I have to ask at this point..depending on a preferred method, is there really a difference in effect, whether one uses a steel or a strop?
That may be vague, but what I mean is, I am recently learning how to strop, and am greatly appreciating it's value, primarily for maintaing an edge after a proper sharpening..I am at a loss now in seeing a difference in view of a steel; am I incorrect in the understanding that both are used in either the last step of a sharpening, and/or to maintain an edge until the next sharpening..so it all boils down to a preferred method for which we prefer..to strop or to steel?
Click to expand...

I've never observed this sort of effect from stropping, not even with compound on wood, and certainly not on such a coarse edge. In my speculations about plastic flow and plain leather stropping I'm imagining it happens only at the very apex and to a much smaller degree. Also, because the steel is an entirely nonconforming surface, there is no pressure spike at the apex which could lead to rounding. So perhaps similar in some ways, very different in execution in my opinion.
 
me2 said:
I have not verfied this myself, but some users report a decrease in edge holding when knives are steeled several times before stoning. Each time it is steeled, it will need it again sooner than last time, until the edge just won't last, or finally breaks off. HH, have you noticed this on your kitchen knives?
Click to expand...

They seem to hold up pretty well aside from being tossed into a draw between use. Until quite recently all I ever used on them (for several years) was a grooved steel to refile the bevel and a smooth one to refine it. In many cases I ignored any remaining burrs or incomplete grinds etc. In fact I always assumed the smooth steel was causing/contributing to the burring when in fact it was probably just standing up the ones left from the grooved steel. The grooved steels I have are very aggressive and seem to be a softer stainless. They leave a grind pattern just as file would and it looks pretty clean at 10-15x magnification.

Until I took these pics I assumed steeling was just a very fast way to put a rather gnarly working edge on a softer knife blade - useful for industry (or my kitchen) but not the sort of thing I'd use on my pocket knives.

These are some very cheap knives - soft Chinese stainless mfg a decade ago or more yet they don't seem to show any kind of edge failure or chipping tho they do not hold a good edge for long even when sharpened with waterstones (with a full blown bevel reset etc - all fresh steel).
BTW i owe an :foot:
 on this whole topic for some of my uninformed comments made in the past re 'steeling'. :)
 
HH, Some other members had similar thoughts on this subject and posted them in the past as well. Yet, its bigger of you to recant. As more is learned on these subjects more is disspelled. Good effort. DM
 
Hi me2!

Wow, thanks for your posts! Very informative, especially your description of the different toughness types and tests. :)

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I agree that the contact area is very very tiny between a knife steel and the blade forms. The resulting pressure (force/area) is probably phenomenally high; probably higher than the yield strength of the knife steel. Not sure how to quantify this. Perhaps one of us (maybe HeavyHanded?) could take a knife with a pristine edge, and just touch the steel to the knife edge, and just move the steel parallel to it's own axis for maybe a few millimeters. This is kind of like using the steel as a "saw" upon the knife edge. The idea is to keep the contact point at the same spot on the knife without moving, and to draw the steel without changing any of the angles. There is movement, so the contact point will smear out and move due to inaccuracies in maintaining the position and contact point. I'm hoping this would be minimized by a short "saw stroke" of just a few millimeters.

I would argue the contact point should be smaller than the resulting spot on the blade. Any resulting inaccuracy in maintaining the angles and positions would mean the contact point would be moving around, and thus generate a larger spot on the blade. This isn't ideal, but at least now, we would have an upper-bound on how big the contact point could be: The contact area is likely to be smaller than the spot we see in the microscope. And ideally, if we did everything perfectly, the spot would be the same size as the contact point, except for the deformation/bending of the blade due to the steel.

It would be most interesting to see if your guess is correct, that the contact area is around 10 square microns! :)

btw, what is the engineering measurement for ductility? You mention that 1095 steel has "1-2 percent ductility." What does this mean, is that the amount of plastic stretching (permanent deformation) the material can undergo before breaking? I'm assuming it is unitless, like strain (unitless because it's basically the ratio of length after to length before).


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You mention fracture toughness, Kic. I didn't understand the description of the mechanical test for fracture toughness. Would you be able to explain it again, or point me to a tutorial about it? I'm quite curious about how it actually works.

btw, it was great to read your discussion about the different types of toughness. :)


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Hi Barrabas!

Thanks for your suggestion that I should contact the user stschmalhaus (Youtube) also known as schmalhaus. I'll send him a message. I know from his youtube channel, he's a very refined knife enthusiast, but I don't know what his background is, if he's comfortable with technical subjects. Worth an ask though!

Here is the book written by Roman Landes:

Messerklingen und Stahl ("Knife blades and steel" according to Google Translate)
Roman Landes (2006)
ISBN: 978-3-938711-04-0
s9GeZ.jpg

Description according to hypefreeblades.com: "A ground breaking work in modern applications of steel for knife edges supported by almost a century of studies on that specific topic. Thus far it is only in German."
http://www.hypefreeblades.com/bib.html


btw, stropping and steeling are rather different. Typically, the strop contains a fine abrasive (such as chromium oxide), and the strop surface is soft or at least pliable. This means a stropping actually removes steel from the knife surface, and the softness of the strop means the knife edge will become slightly convex. Steeling is different in that a smooth steel is extremely hard (harder than the knife steel) and (apparently?) does not remove any steel, and probably puts a micro-bevel on the knife edge (because one typically steels at a slightly larger angle than one sharpens at).

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Hi bluntcut

I'm using the engineer's definition of plastic flow, which is basically any deformation that is non-elastic (ie: permanent). This is a very general term.

Wikipedia lists the general types of deformation:
1. Elastic Deformation
2. Plastic Deformation (also known as plastic flow)
3. Metal Fatigue
4. Compressive Failure (which may or may not be plastic)
5. Fracture
http://en.wikipedia.org/wiki/Deformation_(engineering)
vdvfu.png


It is common for compressing and stretching to cause plastic flow; that just means the sample's shape has an irreversible change, such as a permanent bend.

Not to get too hung up on terminology though! Just when trying to talk about technical matters, I tend to use technical terminology. Not always, though, because I don't understand a lot of technical areas, and because informal understanding is also important to me.

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That's it for now. Pretty busy this weekend, so hopefully I'll have more stuff for everyone later on.

Sincerely,
--Lagrangian
 
I have no idea if these books are any good, but they are what popped up in an Amazon.com search from metallography:

_Metallography: Principles and Practice_ by George F. Vander Voort (1999)
http://www.amazon.com/Metallography...6725/ref=sr_1_1?ie=UTF8&qid=1337540279&sr=8-1

_ASM Handbook: Volume 9: Metallography And Microstructures _ by George F. Vander Voort (2004)
http://www.amazon.com/ASM-Handbook-...63/ref=sr_1_14?ie=UTF8&qid=1337540279&sr=8-14

I see that they both have the same author. If I were interested, I would probably go for the 2004 book over the 1999 book, because there are probably lots of advances in techniques (chemistry, optics, new alloys), and maybe even with computer vision to help measure and quantify stuff. I'm just guessing here; I haven't looked at the book at all.

I'm probably not going to pursue these books in the library or elsewhere. That's only because I don't have any access to fancy metallography equipment or microscopes. So as cool as it would be to learn about metallography techniques, I wouldn't be able to use them.

I list them here, in case some of you were feeling more ambitious and have more/fancier equipment.

Sincerely,
--Lagrangian
 
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HeavyHanded said:
It is my belief that all refining at the high end recruits a certain amount of plastic flow to accomplish its end, be it stropping, backhoning on a waterstone, running on a borosilicate platter with tincture of green (how microtome blades used to be final finished), etc...
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Hi HeavyHanded,

I'm curious to learn more about the microtome knife part. Could you tell us more about "borosilicate platter with tincture of green"? Is this for a metal microtome knife, or a glass one? (I assume it would not be made of diamond like some modern microtome knives?) And is the "tincture of green" something which is applied to the borosillicate platter by the user, or is manufactured into the borosilicate glass?

The simple microtomes I've heard about were simply based on concoidal fracturing of glass; the ones where you snap the glass to produce a very sharp edge. Later on, I learned about metal and diamond microtome knives, as well as the use of ultrasound to help them cut. But I know almost nothing about how metal and diamond microtomes are sharpened.

I'm just freakishly impressed by the sharpness of modern diamond microtomes. They're sharp to 0.005 microns. This is litterally 100x sharper than a modern razor (0.4 microns), and also 1/100th of the wavelength of light which ranges from 0.7 to 0.4 microns. I wish I knew how they sharpened these!

"The radius of the diamond knife edge is about 50 Ångstroms (5nm) or 30 carbon atoms and the entire length of its edge must be defect free to the same dimensions."
http://www.tedpella.com/diamond_html/diamondk.htm
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Sincerely,
--Lagrangian
 
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Tincture of green is a common soap - used to be much more common than today - used for medical prep. I still recall my first few tattoos being prepd with the stuff, has a distinctive odor. As it was described to me an armature holds a steel blade and lowers and swipes it across the spinning platter - much like a record turntable - and flips and repeats the process over and over. Fine slurries of alumox are used initially, with the finishing pass being just the platter and some soap. Not sure if this is how its currently done, my fatherinlaw retired in the 80s, and I'm not even sure if disposable blades were common (they are now). He also described disposable shaving razors as being honed on a spinning iron wheel with a slurry of fine alumox. Again, I have no idea how this is done today. He spent about 20 yrs designing cutters for industry, but chats with him about common knife sharpening do not go far. He uses a 320 grit belt sander followed by a 4000 grit Norton waterstone. Plumbing the depths of metallurgy to apply it to pocket/hunting/utility knives is not something that interests him. A shaving edge should have no tooth, a utility knife should. An edge should last long enough on its intended task to not be a bother re maintenance.
 
I like your Father-in-law's thinking on knife sharping. Ofcourse he had lots of education and experience to arrive at those conclusions. DM
 
HeavyHanded said:
Tincture of green is a common soap - used to be much more common than today - used for medical prep. I still recall my first few tattoos being prepd with the stuff, has a distinctive odor. As it was described to me an armature holds a steel blade and lowers and swipes it across the spinning platter - much like a record turntable - and flips and repeats the process over and over. Fine slurries of alumox are used initially, with the finishing pass being just the platter and some soap. Not sure if this is how its currently done, my fatherinlaw retired in the 80s, and I'm not even sure if disposable blades were common (they are now). He also described disposable shaving razors as being honed on a spinning iron wheel with a slurry of fine alumox. Again, I have no idea how this is done today. He spent about 20 yrs designing cutters for industry, but chats with him about common knife sharpening do not go far. He uses a 320 grit belt sander followed by a 4000 grit Norton waterstone. Plumbing the depths of metallurgy to apply it to pocket/hunting/utility knives is not something that interests him. A shaving edge should have no tooth, a utility knife should. An edge should last long enough on its intended task to not be a bother re maintenance.
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Hi HeavyHanded,

Thanks! Very interesting :)
Even if your father-in-law was not interested in metallurgy, he must have had very deep hands-on knowledge and very deep practical experience about how to do highly refined sharpening and cutting. I would've loved to have talked to him about cutting and sharpening in whatever context he would wish to chat about (any blades in any context, even if not everyday cutting).

I don't know much about aluminum oxide, but it appears that it comes in very fine powders. For metallography polishing, it seems to be easily purchasable in grits as fine as 0.05 microns. http://www.emsdiasum.com/microscopy/products/materials/polishing_supplies.aspx

I suppose that for an extremely refined edge (like for a microtome), one could use a softer abrasive if the grit size could not be reduced. However, since that might cut slower, it may not be a good trade-off for mass-production. There's also stuff in chemistry about "colloidal suspensions" which are sometimes created by chemical precipitation, I think. I suppose if the chemistry is done right, the precipitate particles could be super fine? I'm not sure since I'm not a chemist.
http://en.wikipedia.org/wiki/Colloid#Preparation_of_colloids

I find it interesting that they used a spinning glass disc (either a glass or iron). Glasses have no micro-crystaline structure, so they could form an ultra-smooth surface. As for iron, I'm not sure it would be as smooth, because of the metal grain structure. Fine polishing on a spinning disc reminds me of how diamonds (and other gems) are cut and polished on spinning copper wheels with diamond dust. As you've probably seen in pictures and videos, the gem is held against the wheel by a special armature and maintains a very precise angle for cutting/polishing. Technically this is a form of lapping or polishing, where the abrasives embed into the softer copper; seems quite similar to stropping in concept. For gem cutting, this method doesn't seem to have changed much over the years (decades? centuries?) which suggests, to me, that it is already a very refined technique.

Sincerely,
--Lagrangian
 
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You are correct Lagrangian. Ductility is measured 2 different ways for tensile samples. First, as you say, it is percent elongation, or how much does the specimen permanently stretch from it's original size. I have seen 25% or higher for common concrete reinforcing bars. 8 inch samples were over 10 inches long when they broke.

The other way is percent reduction in area. Ductile failure is preceded by a narrowing of the specimen in a small region where the break will occur. This is called necking. The original cross section area is compared to the reduced cross section. The percentage values tend to be a little higher than % elongation values for the same sample. 25% elongation may be 35% reduction in area, or something like that. When ductility is specified, which one to use should also be specified.

I'll have to dig into the Kic determination. It's pretty involved. The lab I use for that type of work only charges $50 for tensile tests, but characterizing Kic is $1000 or so. The test I described wasn't for Kic. It is a tensile test for material with such low Kic that it can't be placed into a normal tensile machine, where jaws or threaded inserts hold the specimens. It's basically a flat plate of the test material supported freely by 3 ball bearings, with a load applied in the middle. A fairly long equation (which I can't remeber) gives the tensile stress of the center of the specimen. You bring up a good question. I really should know how Kic is determined. We usually just looked it up in a table.

I'm also curious about how large the contact area is. My SWAG (scientific wild ass guess) had the stress at contact over 3,000,000 psi., much greater than any cutlery steel I know of, which max out at around 450,000 psi or so. Most are considerably lower than this.
 
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