RE Stropping

[Sadden]

In a previous thread someone mentioned that a strop , irregardless of the substrate , always removed toothiness. So today I did some testing , just for my own interest and got some interesting results I thought I would share.

I have a brand new Cold Steel Warcraft Tanto (CPM 3V) , Factory edge , never used except to cut some paper for testing purposes. My goal was to see how a strop would affect this factory refined toothy edge. I suspect that cold steel finished this knife on some kind of coarse diamond belt. 600-800 maybe? Unlike traditional cold steel knives this one was not shaving sharp. Currently I've only been working the one side of the bevel just so I can look back on the factory bevel and compare.

So I grabbed my Kangaroo Leather Strop , and some 15micron CBN. This is all brand new stuff , never used. Applied the CBN in a sterile setting , and spread it using a sterile glove. (I had to change gloves several times as I was also applying my 9 , 4 and 2 micron CBN on separate strops). So now we have a clean strop loaded with nothing but 15micron CBN.

Took it to the EP and my new knife and started working on one side. Within 5 minutes I had formed a burr. Yes I formed a burr using a strop. The finish on this WC Tanto must be really quite coarse as even after significant work not all the factory scratches are removed. Im not chasing a mirror , nor am I even trying to sharpen the knife. Although the edge is improving significantly compared to the factory edge. FWIW , the 15micron is equal to about a 1k shapton , plenty toothy.

I think that its pretty evident that stropping is all about the compound , with the substrate playing a minor role* until you get to the really fine stuff where the abrasive in leather is actually coarser than the compound your trying to use (below 1/10th of a micron). A quality compound may cost more. But cost per use is much lower compared to cheap "compounds" and "improvised compounds". If you don't know what the abrasive is and how much of it your getting then don't buy it. Period.

Heres some pictures , these actually have very little to do with what I was talking about above , but they clearly show how much metal is being removed by a strop. Loaded with a quality compound. Ken Schwartz' CBN in this case.

Bare Roo


Compound applied (9Micron Here)


And compound applied and then used (the 15 and the 9 looked identical after being applied to the strop this merely illustrates metal being removed from the blade)


*So long as you are using a firm substrate with little give , and the substrate has an inherently finer natural abrasive than the compound being used. Such as Kangaroo Leather Balsa , or Nanocloth which has no abrasive until you load it , and will not affect an edge without a compound applied to it.

 

[HeavyHanded]

There needs to be a second phase to this test before drawing conclusions. The stropped edge (and it could stand to have the stropping treatment done a few times. No harm if its not rounding anything) should be verified as having had a flat bevel before starting. A handful of passes on a relatively fine hone and see how the scratch pattern is developing should tell you plenty. And then the same test after multiple stropping operations, and see how the curve of the bevel compares to a flat fine diamond plate or ceramic stone. If the stone reveals a flat plane from shoulder to apex - success. Raising a burr does not indicate a flat plane.

 

[ksskss]

"There needs to be a second phase to this test before drawing conclusions. "

There needs to be a clearly stated premise to test before a conclusion can be made. If we take the premise that a burr can be produced using a strop as the thing to be proved or disproved, and further that the rate of burr formation is related to the particle size of the compound on the strop, then I fail to see the relevance of whether the edge is flat or has some degree of convexity. Indeed one must specify the degree of convexity if you feel it is a relevant parameter, which I feel is not a relevant parameter. A precision guided device like an EdgePro, WEPS, etc produces an edge with less convexity than freehand sharpening as the degree of angle control is greater. A very thin strop with less give such as a kangaroo strop or a thin sheet of paper, both supported on a flat surface, will only produce convexity proportional to the control of the angle relative to the abrading surface. On the other hand if the strop is powered, such as a leather belt on a belt grinder with a flat platen for support, using a light touch, one generates a very small amount of convexity. If the slack portion of a leather belt is used one generates a great deal of convexity, roughly proportional to belt tension and forces applied through the knife against the substrate. Using a coarse grit such as a 15 micron particle of CBN in ALL of these instances, I have been able to generate a burr. So in my experience the radius of curvature of the edge is not a relevant variable. Even if starting with a flat grind and converting it to a convex grind or vica versa, in all instances I have been able to produce burr. Of course when comparing bench stropping to powered stropping the total length of stropping in inches during the procedure is typically far greater with powered stropping, more than satisfying the requirement of doing stropping a few times.

Indeed, in my testing, one can produce burr with much finer compounds than 15 microns on a strop (using the term in the most generic sense). This is done at a proportionally slower rate of course with finer compounds and is more related in time to the work required. If the edge is very close to having the two sides meeting, burr formation will occur more rapidly immediately after the two sides have met. If the previous burr is removed by tearing it off as opposed to abrading it off, the gap will be larger and the time required to produce a subsequent burr will take longer.

---
Ken

 

[HeavyHanded]

"There needs to be a second phase to this test before drawing conclusions. "

There needs to be a clearly stated premise to test before a conclusion can be made. If we take the premise that a burr can be produced using a strop as the thing to be proved or disproved, and further that the rate of burr formation is related to the particle size of the compound on the strop, then I fail to see the relevance of whether the edge is flat or has some degree of convexity. Indeed one must specify the degree of convexity if you feel it is a relevant parameter, which I feel is not a relevant parameter. A precision guided device like an EdgePro, WEPS, etc produces an edge with less convexity than freehand sharpening as the degree of angle control is greater. A very thin strop with less give such as a kangaroo strop or a thin sheet of paper, both supported on a flat surface, will only produce convexity proportional to the control of the angle relative to the abrading surface. On the other hand if the strop is powered, such as a leather belt on a belt grinder with a flat platen for support, using a light touch, one generates a very small amount of convexity. If the slack portion of a leather belt is used one generates a great deal of convexity, roughly proportional to belt tension and forces applied through the knife against the substrate. Using a coarse grit such as a 15 micron particle of CBN in ALL of these instances, I have been able to generate a burr. So in my experience the radius of curvature of the edge is not a relevant variable. Even if starting with a flat grind and converting it to a convex grind or vica versa, in all instances I have been able to produce burr. Of course when comparing bench stropping to powered stropping the total length of stropping in inches during the procedure is typically far greater with powered stropping, more than satisfying the requirement of doing stropping a few times.

Indeed, in my testing, one can produce burr with much finer compounds than 15 microns on a strop (using the term in the most generic sense). This is done at a proportionally slower rate of course with finer compounds and is more related in time to the work required. If the edge is very close to having the two sides meeting, burr formation will occur more rapidly immediately after the two sides have met. If the previous burr is removed by tearing it off as opposed to abrading it off, the gap will be larger and the time required to produce a subsequent burr will take longer.

---
Ken

The assertion I made was that stropping on a conformable leather strop will produce a finer scratch pattern (less toothy) than one would get with a similar abrasive on a hard surface, and this conformable nature will round the cutting plane. One sheet of paper over steel, glass or stone, in this case constitutes a "hard surface". Even boiled leather is not as hard, and would have to be treated with a polymer or wax etc to make it hard enough that undesirable convexing wouldn't occur, or that the particle in question will make an apex profile that would be "toothy", and this treatment will effect how the abrasive functions. This is relevant for long term maintenance, especially of a "toothy" edge. Lacking from this discussion is what a toothy edge is, we might all be describing he same thing from different baselines. Also lacking is a general agreement on what constitutes "stropping" - for the purposes of this discussion I'm talking about veg tanned leather, with or without casing, and in the context of maintaining a toothy edge, or even creating one in the first place.

One can certainly get a burr to form at almost any level of polish with enough pressure and especially if some loading has occurred, as long as the backing is hard. On conformable leather the particle needs to be larger than what one could use on a harder surface.

IMHO every two degrees or so/side yields a noticeable loss of cutting efficiency, whether the grind is flat or convex, so a rounding of 2-3 degrees/side makes a loss of 6 degrees overall - big difference between 24 and 30 inclusive, or 30 and 36, on most tools.

Stropping on a powered belt is not the same as repeated hand stropping, steel elongation and burr formation are greatly influenced by speed.

The level of conxexity only an issue if it becomes progressive or was undesirable from the start, as I stated the conformable strop, even thin leather, will remove more material from the apex than from the back bevel due to it expanding to fill its previous space. Certainly less and less pressure will reduce this tendency and also the abrasive will then bite with less and less authority - taking its toothy edge with it. Either way, IMHO it is not an efficient method of creating or maintaining that sort of edge compared to other options. There are other forms of stropping I mentioned in the first response - waterstones, jointer stones, paper over a stone etc. Can one pound a square peg through a round hole? When there's work to be done, get comfortable with the right tool for the job, don't force a tool you're comfortable with to fill a role it isn't good at. Leather is king for making a smooth push cutting edge, no argument.

 

[Obsessed with Edges]

(...) One can certainly get a burr to form at almost any level of polish with enough pressure and especially if some loading has occurred, as long as the backing is hard. On conformable leather the particle needs to be larger than what one could use on a harder surface.

Agreed.

I managed to create a burr big enough to catch my thumbnail, by stropping on a bare piece of plywood yesterday. No compound at all. So I completely agree, it's more about pressure (which is greatly affected by hardness/softness of the backing), and less about the compound.

The aggressiveness of a given compound will vary widely, depending on the softness vs. hardness of the substrate into which it embeds. This is easy to see when comparing the black marks left by swarf on ordinary veg-tanned leather (let's say ~7 oz.) vs. a wood strop, using the same compound. 1 micron diamond is a good test for this, and it's why I started using it on balsa for more 'bite', and stopped using it on leather, which tended to over-polish (w/edge-rounding) with the same compound. Even 'soft' balsa will make a given compound work much more aggressively than on ordinary leather of any appreciable thickness. A particle of a given size can't dig nearly as deep into the steel, if it's being compressed/absorbed into a soft footing, under the pressure of the blade, at the same time. When it doesn't dig as deep, it's effectively performing to a finer (polishing) degree, and less able to leave the 'teeth' we might hope to create.


David

 

[ksskss]

We are substantially in agreement on any number of points, but of course we are a bit apart on others, so it is worth further discussion and synthesis of our ideas. Thanks for the effort of your response.

"The assertion I made was that stropping on a conformable leather strop will produce a finer scratch pattern (less toothy) than one would get with a similar abrasive on a hard surface, and this conformable nature will round the cutting plane."

Ignoring the statement that a cutting plane is rounded - therefore it is no longer a plane, I get the jist of the statement. In large measure this fineness is indeed due to the 'give' of conformability of the substrate, but what is relevant is that the particle embeds more in the more conformable substrate. Thus if you have a particle of say 15 microns on a very hard substrate, infinitely hard for discussion's sake, all 15 microns are 'sticking out'. If it is very soft the particle more deeply embeds in the substrate and only 'peeks' out, so it effectively acts as a smaller particle but with a wider radius than a smaller particle on a harder surface. There is the other factor that if you are using a very hard substrate there is more of a tendency for the particle to roll around on the substrate. This produces a different sort of scratch pattern when the particle is more affixed to the platen or substrate. Now if you have a hard surface with many 'pores' smaller than the particles applied well now you have a hard surface with smaller amount of the individual particles exposed.

But this is a minor effect compared to the consistency that the edge is held to the abrasive surface. Indeed most freehand sharpeners will introduce more convexity due to movement variability, both on hones and strops.

"One sheet of paper over steel, glass or stone, in this case constitutes a "hard surface""

Exactly! Now this is why Kangaroo leather excels in this regard. It is the thickness of an index card so it presents a "hard surface", compared to thicker leathers like horse and cow leather. Please contact me for a sample for you to test this yourself. The surface texture is also finer and less abrasive than horse or cow leather, making it the 'tool for the job' moreso than thicker substrates. Here we have a point of potential agreement. Thicker substrates DO round edges more as there is more distance for 'give' just like a stack of paper 'gives' more than a single sheet.

"Lacking from this discussion is what a toothy edge is, we might all be describing he same thing from different baselines. Also lacking is a general agreement on what constitutes "stropping" - for the purposes of this discussion I'm talking about veg tanned leather, with or without casing, and in the context of maintaining a toothy edge, or even creating one in the first place."

Agreed. Toothy and stropping are both poorly defined terms and result in endless confusion. Stropping is classically referring to leather strips used for horses historically, however some interpret it a just leather strops and some more broadly including all sorts of substrates. Further some refer to the edge trailing motion associated with using leather strops, so one sees discussion of stropping on stones, paper etc. Others only associate stropping as neither restricted to leather or the motion, but rather particle size, so the notion of stropping on say an 80 micron particle is excluded. So if one is using edge trailing strokes only on a stone, this is stropping? Going in both directions is honing? Using a 30,000 grit stone edge trailing is stropping as is putting a stropping compound on the stone.

As you can see this is a hopeless mess. So in more precise discussions such as this I simply prefer the more inclusive term abrasion and simply defining the substrate, grit, particle type and other aspect of the abrasion process.

.....

 

[ksskss]

(continued)

Toothy is similarly messy. Simply looking at the level of finish of the bevel isn't enough although that is commonly what is described. If you break off the burr - eg with running it through felt wood, etc, you create a surface at what was the edge that is quite toothy. It is a fracture plane and will be completely different than the toothiness of an edge properly formed at the same grit where the edge is not left in this broken off state.

Now when you get into natural stone scratch patterns the concept of toothiness reaches yet another level of complexity in terms of describing the toothiness of an edge. But that's a bit outside the bounds of the current topic.

"One can certainly get a burr to form at almost any level of polish with enough pressure and especially if some loading has occurred, as long as the backing is hard. On conformable leather the particle needs to be larger than what one could use on a harder surface. "

Yes burr formation is increased with increased pressure and that is easier to produce on a harder surface. But even on a slack surface burr formation can occur, albeit with more time and/or pressure. As I previously mentioned this is largely due to particles embedding more easily on softer substrates and thicker substrates.

It is probably worth a bit of off topic discussion regarding stones. You can't consider them all as being of equal hardness. Indeed the mud on the stone presents an interesting issue here. Thicker mud will produce more edge convexity than thinner mud and, especially for single bevels, produce a higher degree of conformability on irregular surfaces such as many single bevels with less than a perfectly coplanar surface. Interestingly you can modulate this by taking mud from a stone and applying it to a paper strop, presenting a harder surface than the original stone presents if the paper is backed by glass or a softer surface if the paper is backed by your finger tip of neoprene for instance.

"IMHO every two degrees or so/side yields a noticeable loss of cutting efficiency, whether the grind is flat or convex, so a rounding of 2-3 degrees/side makes a loss of 6 degrees overall - big difference between 24 and 30 inclusive, or 30 and 36, on most tools."

Well it yields a different geometry. The result is more or less desirable depending on the task. IF you require a more robust edge, this can even be desirable. So if a flat grind is failing for the task at say 10 degrees per side - chipping or rolling for instance, slightly increasing the angle can be to advantage. You see this with hamaguri grinds and with flat and convex microbevels. Of course cutting efficiency is also largely codependent on the level and type of finish for the task as well. It simply needs to be taken into account in determining optimal edge geometry. But yes on a softer more conformable substrate edge rounding can occur and should be considered. Now if you are performing precision stropping, one useful trick is to determine the angle at the edge of the edge by determining the angle where the edge bites into the substrate (gently, so as not to damage the stone/strop) whether it be a strop or soft stone and go slightly more acute than that. This will produce edge thinning on both a strop and stone, giving you a more acute angle and polishing behind the edge. Here you are approaching the edge and not at risk of producing unwanted premature burr formation.

Of course if you hone or strop at the angle of the 'edge of the edge' you inherently tend to go to steeper and steeper angles. Avoiding this is a matter of technique. You often see freehanders doing this with a series of stones, producing an ever more obtuse convex edge as they escalate to finer grit stones. You need to be cognizant of what final angle at the edge of the edge you wish to produce - convex or flat grind.

"Stropping on a powered belt is not the same as repeated hand stropping, steel elongation and burr formation are greatly influenced by speed. "

Yes there is a continuum here. If I use a variable speed grinder, mine is capable of moving the leather or other belt at speeds as slow as a hand bench strop or of course far faster. Speed is certainly a relevant variable for rate of burr formation at a given grit and one I can control with the setup I have, duplicating hand stropping at the low speeds. Not quite sure what you are referring to regarding steel elongation (heat effect?)

Regarding your summary paragraph, again many points of agreement making an edge - convex or flat - get less and less acute from rounding from it's optimal geometry is undesirable. Using thin leather or paper over a hard backing allows you far greater control of your edge geometry allowing you both the option for thinning and not increasing final angle geometry. What is the right tool for the job? Now this gets interesting. Would a stone with an abrasive content - even a hard stone - that doesn't cut as quickly through an abrasion resistant steel vs an abrasive like CBN or diamond that has a more rapid cutting rate on say a belt grinder be the ideal tool? I can easily get an edge sharper and faster on abrasion resistant steels on a belt with CBN or diamond than one can get with a stone. I can also take that same stone that won't effectively cut through high vanadium content steels and 'dope' the slurry with CBN or diamond and make it perform considerably better. The right tool can be a topic of endless discussion

---
Ken

 

[Sadden]

Hmmmm , well I've been thinking on this for a little bit , I tried taking some pictures to better illustrate what I am talking about but lets clear the air on a couple things in the meantime.

In this particular experiment. I was only trying to prove that a strop can create a toothy edge. I one-upped myself by raising a burr with an EP Strop.

The strop that was used was Kangaroo Leather , and not Cowhide or Horsehide or an old leather belt (as many here recommend). The reason I use kangaroo on 14 out of my 23 strops (the other 9 being nanocloth with 3 or 4 more roo strops to come) , is that it much thinner than all the aforementioned leathers. And when Ken makes these strops he stretches it as thin as possible. This minimizes compression and therefore convexing. This also applies to nanocloth , but it has even less give than roo and has no inherent abrasive. I use very light pressure , so any amount of micro convexing has been significantly reduced. Do my edges that I strop have some microconvexing? Maybe? Aside from being extremely difficult to prove one way or another , it actually has nothing to do with my original purpose behind this experiment. Again , all I wanted to prove was that a strop can in fact create a toothy edge. Ken also offers , 30 , 45 , 80 , 200 and even 300 micron CBN. Im just tickling the surface on this.

Ken makes a good point regarding terminology and how its all very vague and muddy. To me , an 8k shapton is "toothy" , while many call that polished. And 16k and 30k Start to develop polish. And above 30k becomes "sticky" sharp. I can treetop hairs off an 8k shapton.....

Im going to be adding some coarser compounds to my lineup in the near future , so I will be revisiting this. Hopefully tomorrow I will have my Camera working so I can take some pictures and illustrate the difference between Kangaroo Leather and veg tanned leather. My pictures with my cell phone looked fine , until I got them onto the computer to look at............

 

[stitchawl]

..................... Hopefully tomorrow I will have my Camera working so I can take some pictures and illustrate the difference between Kangaroo Leather and veg tanned leather.

Is your leather from the belly cut or the shoulder? Makes a VERY big difference in its properties. Will this be properly processed veg tanned leather or straight from the shop? By 'properly processed' I mean cased and rolled for about 15-30 minutes. Makes a VERY big difference.

Properly prepared leather for strops shouldn't be much more compressible than Oak or Maple. But then, proper stropping pressure shouldn't be enough to compress any but the softest surfaces in the first place, except at the micron level, or we're doing it wrong.


Stitchawl

 

[Sadden]

Im going to have to do some.digging and see what i can come up with. I have a buddy who does leatherworking so it might be worth a call to him.

 

[HeavyHanded]

We are substantially in agreement on any number of points, but of course we are a bit apart on others, so it is worth further discussion and synthesis of our ideas. Thanks for the effort of your response.

You are very welcome, I try not to spend too much effort defending my personal preferences - have learned a great deal and discarded even more. I frequentIy get drawn into supporting other people's assertions more than my own. I also try not to speak in terms of absolutes - everything is in context when it comes to most aspects of sharpening.

........But this is a minor effect compared to the consistency that the edge is held to the abrasive surface. Indeed most freehand sharpeners will introduce more convexity due to movement variability, both on hones and strops.

Most freehand sharpeners go to great lengths to reduce this tendency down to a bare minimum, and at least learn to identify and restrict this to predictable tolerances. When you can go from one mechanism to another and back again with very little or no visible indication of edge convexity especially along the apex, you're doing well. This a very good indication that the method under consideration is suitable for long term, predictable use, and that your technique is strong. If you choose to induce some convexity, that's fine. When its an unintended by product, no longer fine.

..........As you can see this is a hopeless mess. So in more precise discussions such as this I simply prefer the more inclusive term abrasion and simply defining the substrate, grit, particle type and other aspect of the abrasion process.

Yes, basically there are

Grinding - fixed abrasive, hard surface
Lapping -loose abrasive, hard surface
Sanding - fixed abrasive, conformable surface
Burnishing - no or minimal abrasive, hard surface

And the grind direction for the bulk of the finishing work (leading, parallel, trailing, and at what angle relative to the cutting edge)

Of course now the discussion shifts to areas of overlap such as stropping, muddy stones, slurries, loosely bound abrasives in a "softer" vitreous or resin binder etc

And characteristics of various abrasives, shape, friability, relative hardness

And how they are fixed to their respective backing surface. IMHO this is an often overlooked area - it took a lot of experimentation to come up with a binder that worked better on paper than what was commercially available for polishing - generally stearin but can include all manner of carriers and vehicles. The presence of these in the right proportion can make a mediocre or poorly performing abrasive into a powerhouse. The inverse is also true.

Also included in this, as it becomes an increasing factor to be managed with higher stock removal rates on a limited surface area - how to deal with metal removed during process. This is where I find leather to fall short for more aggressive stock removal - its not feasible to throw out pieces of kangaroo leather with any frequency. On a limited working surface, the presence of swarf can significantly impede abrasive action and rate. Now we are cleaning the leather and possibly changing its characteristics relative to the abrasive we dose it with. For the purposes of the discussion, we can assume freehand, unpowered activities?





....

 

[HeavyHanded]

-----

.......Toothy is similarly messy. Simply looking at the level of finish of the bevel isn't enough although that is commonly what is described. If you break off the burr - eg with running it through felt wood, etc, you create a surface at what was the edge that is quite toothy. It is a fracture plane and will be completely different than the toothiness of an edge properly formed at the same grit where the edge is not left in this broken off state.

Now when you get into natural stone scratch patterns the concept of toothiness reaches yet another level of complexity in terms of describing the toothiness of an edge. But that's a bit outside the bounds of the current topic.

Again, for purposes of discussion we should assume a clean edge, formed by abrasion, burnishing, or both. Also, if the edge was formed with a trailing or leading stroke and what sort of post abrasive finishing was used/needed to get to a clean edge. Included must be considerations of consistency/repeatability and relative cost. For purposes of discussion is always difficult to pin down, as many people seem to think of a simple formula where the abrasive size determines edge width, which is not the case. So unfortunately we're stuck with a looser definition that has to include the presence of irregularities along the cutting line when viewed in profile and/or when viewed from above, and how pronounced these irregularities are. More loosely even, maybe defined as an edge that has cutting advantage (requires less pressure) when draw cutting over a more uniform edge at the same inclusive angle and profile. Still room for wide interpretation, and a very subjective term when applied across a variety of preparation methods. Have to remember, this entire discussion started with a very casual question about making an edge a little more bitey.

Yes there is a continuum here. If I use a variable speed grinder, mine is capable of moving the leather or other belt at speeds as slow as a hand bench strop or of course far faster. Speed is certainly a relevant variable for rate of burr formation at a given grit and one I can control with the setup I have, duplicating hand stropping at the low speeds. Not quite sure what you are referring to regarding steel elongation (heat effect?)

I am speaking of the tendency of steels to exhibit greatly reduced elongation before failure at higher testing speeds, and also making a bold assumption that this property relates somewhat to burr formation. A burr, at least in part (theoretically), forms as a result of tug-of-war between properties of the steel and the qualities of the particular abrasive (shape, pressure) or cutting tool. Am not the first person to note that an edge prep'd at high speed on a belt will look and perform differently than an edge prep'd by hand with the same belt. Likewise there will be a lesser tendency to form larger burrs at high speed. On a high speed polishing operation, there is also less tendency for the bevel to sink into the substrate. Difficult to draw conclusions across methods, even when using the same abrasive and substrate.

-----

 

[HeavyHanded]

....... The right tool can be a topic of endless discussion
---
Ken

I totally agree with this. From my viewpoint I strive for a few guiding principles:

The entire process should be repeatable with a high degree of consistency.

It should require the fewest number of steps to be managed, and the largest margin of error possible for each step.

It should work well with the intended use of the tool - ie, a handful of strops not practical for backpacking, fine in the kitchen - a bench sander not practical for an axe in the field, perfectly acceptable for a shop tool.

It should be inexpensive while maintaining effectiveness.

To keep this entire conversation in context, it arose from a response to someone looking for a bit more aggressive edge. IMHO, the advice to simply try his existing abrasives on a harder backing, or stopping at the stone and using plain strops at a bare minimum, is far more practical then spending a bunch of coin on kangaroo and CBN when we don't even know if the gentleman is using high carbide content steel.

Not so much an issue of what can work, but of what works with the largest margin of error and least fuss - what someone reading along can attempt on their own. FWIW, in my first response in the other thread, I mentioned using black emery on leather, so am not fanatically opposed to the practice. Over time however, I find it doesn't work well and one has to go back to the stones more often than they might using other methods. The leather "tames" the abrasive - whatever it happens to be (why it works so well for finer polishes), and increased pressure to restore/maintain the tooth will increase rounding. I've demonstrated this to myself using very thin leather over stone - not as thin as the 12pt card stock thickness of kangaroo, but approx 2mm boiled and stretched. The amount of convexity at the apex can be considerable with the slightest amounts of give under some circumstances.

Anyone familiar with my posts knows straightaway that I'm a big proponent of experimentation and NOT taking other people's word without some testing of their own. By all means, anyone reading this or curious about how to make various edge strategies should try a bunch of options and see for themselves - there are a ton of variables to play with. Have fun, but take notes....


ETA: had to bust my reply up into pretty small pieces, what is the total character count for a post anyway? I can't recall ever going over.

 

[Magnaminous_G]

Why would you put compound on kangaroo leather?

 

[Sadden]

Why would you put compound on kangaroo leather?

Because its the smoothest , thinnest , finest grained with the smallest silicates of any other leather (including equine). It compresses the least inducing the least convexing possible making it ideal for stropping. It takes especially well to the fine compounds.


I had to get a new charger for my camera so some new pictures will be coming in a couple days.

 

[HeavyHanded]

I'd love to see the science behind this. Natural silicates present in organs and skin are already mighty fine, if I'm not mistaken, beyond reach of an optical microscope at sub .2u, also water soluble. Most are present as forms of silicic acid IIRC, and not as silica dioxide. I'm not disputing anything, but would love to see a research paper on this topic if anyone can link to it.

 

[Sadden]

There are some SEM images floating around somewhere. I might have to see where I can dig up the link. Your right on the money as far as silicate size , this is why compounds below 0.1micron need to be used on nanocloth , which has no abrasives.

 

[HeavyHanded]

Wouldn't you need a SEM to see a difference in finish luster with compounds under .25u? Optically, there should be no visible change, even at 1000x. Another consideration, those natural silica are embedded in the leather (assuming they're present as an oxide), not just pressed into the top. They can't be acting at anything like a .2u abrasive. I'm just ruminating here...

 

[Magnaminous_G]

I dunno. I think putting compound on Kangaroo leather is like putting A1 sauce on a Lawry's prime rib.

 

[stitchawl]

The amount of natural silicates in leather is a direct result of the food the animals have been eating. Kangaroo feeding on grass would have no greater concentration of natural silicates than horse or cow fed on grass. Most cowhide comes from animals that have been raised for food, fed synthetic diets to increase size and weight quickly, rather than allowed to graze the North 40 before being harvested for meat, which is why horsehide tends to have a greater concentration of silicates than commercial cowhide. Horsehide and kangaroo hide have roughly the same concentration of natural silicates.

However.......

Proper preparation of the leather (i.e. casing and pounding/rolling, etc.,) forces the natural silicates to the surface of the leather, increasing the concentration found there. This is true regardless of the animal hide used. If you start with a thicker hide and prepare it correctly, there will be a higher concentration of silicates in the surface of the hide. If you use a thin split of kangaroo hide that has NOT been prepared before splitting, there would be far LESS natural silicates on the surface than if you were to use a hide of full thickness and case/pound it and THEN split it.

Unprocessed Kangaroo hide that has been split will have LESS silicates on the surface than a thick cow hide that HAS been properly processed. And, being properly processed, that cowhide will be extremely dense with no appreciable surface flexing to round an edge.

You DO get to tell people that you are using Kangaroo hide though... That should account for something.

As for putting compounds on top of Kangaroo... well... that makes absolutely no sense at all. Unless one is using a compound smaller than .01 micron, all you are doing is covering up the tiny natural silicates with something larger, and we all know that doesn't do much good!


Stitchawl