Effect of the Kangaroo Tail Strop on Sharpness

cudgee said:
I have never seen the washboard system before. Very interesting, what is your opinion of this system?
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The Washboard works on similar principles as a serrated contact wheel on a belt grinder - the reduced footprint makes the contact areas more aggressive, the non-contact areas have greatly reduced tendency to dub or round the edge.

On the washboard the textured teeth actually compress the paper at the contact points, allowing materials like wet/dry and regular copy paper to take on characteristics of a stone. This increased spot pressure also reduces chance of glazing the abrasives on wet/dry. It can maintain a flatter edge bevel than wet/dry over a steel plate at greater then 2x the applied force.

Used with plain paper you can apply enough force to actually burnish low carbide steels without chance of drawing the edge out. Used with compound and paper, it can refine and repair an edge with a great deal of latitude in terms of applied pressure. On the site I show how it is able to sharpen an edge with a great deal of wear, using only paper and compound.

Edges stropped with it are effectively more coarse/toothy than ones done with the same honing compound on paper over a smooth hard surface (steel plate). The failure mode if pressing too hard is the apex fracturing off, rather than the apex dubbing over.

No longer for sale (ran out of all my stock), but hope to get back up and running in the near future.

Serrations
Serrations are uniformly spaced grooves cut at an angle across the face of the wheel. The belt is now effectively supported by the "lands" or uncut portion of the wheel face. This reduces the effective area of contact of the abrasive with the work and makes the wheel more aggressive than a smooth face wheel of the same hardness. The narrower the lands and wider the grooves, the more aggressive the wheel becomes.
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https://www.emisupply.com/catalog/article_info.php?articles_id=14&<osCsid>
 
I have definitely noticed that stopping increases my edge. I was always worried a hanging strop would cause the edge to round though I am sure I must be missing something.
 
Just like a regular strop, it depends on the angle of the knife to the surface, whether is on a board or a hanging strop.
 
j_d said:
I have definitely noticed that stopping increases my edge. I was always worried a hanging strop would cause the edge to round though I am sure I must be missing something.
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Do not use any honing compounds at all on the hanging strop, and let the burnishing work. As we know, the burnishing displaces metal not abrading it.
With burnishing we do not risk abrading off the ultra-sharp apex of the edge, no risk of "rounding the edge".

After Todd Simpson showed us in the Scanning Electron Microscope what a plain hanging strop does to the edge, we use no honing compounds, no abrasives on our Kangaroo hanging strop. Micro-convexity imparted by the hanging strop makes the edge stronger, improving the edge retention.
 
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Another example of wire edge removal by plain hanging strop in the stropping step of our video How We Sharpen Japanese Knives on Tormek - jump to 12:50
 
Does a hanging strop perform differently from a flat strop used at a slightly elevated angle? How/why?
 
Typically, firm strops are used pasted for abrasive stropping, while the hanging strop is used plain (w/o any honing compound) for finishing.

Both are to remove the root of the burr. The burr root is a scientific term, you may hear some call it the base of the burr. We take a blade to the strop having removed the bulk of the burr by other means of honing, AFTER we cannot palpate the burr (cannot feel it by brushing the finger across the edge).

Hanging strop is more pliant, "giving in", than a firm strop.
The firm leather strop is compressible only to a degree, and even in high-angle stropping can shape the root of the burr into the wire edge.
While the hanging strop "wraps" over the edge apex - this difference explains why the hanging strop removes the root of the burr better.

We define wire edge as a product of burr honing, when the burr root is shaped into an edge rather than deburred.

In our sharpening, knives of low HRC ductile knife steel often show residual burr even after high-angle honing on a rock-hard felt wheel, leather or paper wheel with fine diamonds - finishing these blades on the plain hanging strop helps to clean the apex of the burr root, and we can see instant improvement of sharpness on the tester.
Contrary to them, knife steels that are prone to form "negative burr" can be cleanly deburred with firm stropping at the edge angle or a little higher than edge angle, using the finest abrasive.

But I haven't done a comparison of plain firm to plain hanging stropping as this makes little sense in view of what we know about the burr formation and removal.
 
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wootzblade said:
But I haven't done a comparison of plain firm to plain hanging stropping as this makes little sense in view of what we know about the burr formation and removal.
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I thought I was understanding until I got to this line. I would be quite interested in this comparison and I don't see why it doesn't make sense. I have a hanging strop but I only use it on razors where the spine acts as an angle guide. I wonder if there is a reason to develop the technique to use it on other blades rather than just using a paddle strop either freehand or on a jig. Using a more compressible leather seems like a simpler route if "wrapping" is needed?
 
Mr.Wizard said:
I thought I was understanding until I got to this line. I would be quite interested in this comparison and I don't see why it doesn't make sense. I have a hanging strop but I only use it on razors where the spine acts as an angle guide. I wonder if there is a reason to develop the technique to use it on other blades rather than just using a paddle strop either freehand or on a jig. Using a more compressible leather seems like a simpler route if "wrapping" is needed?
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My logic is straightforward here: if the firm strop with a fine abrasive not always removes the wire edge, why would plain firm strop do.
 
I don't know. Why would a hanging (plain) strop? Why would a hanging strop do something that a flat strop does not if the edge is made to interact with it at the same angle and pressure? I would really like to know if you see the same improvement using the 'roo strop pulled tight over a wooden board or block, but obviously I cannot compel you to try it. Anyway, thanks for the report and encouragement to experiment with hanging strops. My horsehide strop is very stiff by comparison though so I don't know if I will get the same effect.
 
In my experience, a plain strop at/near the bevel angle will never remove a foil, unless it is folded over first (by cutting into wood or plastic, for example). Alternatively, if you strop like you are buttering toast, it will break it off nicely.

If you are seeing an improvement with just handful of stropping strokes at the bevel angle, it's almost certainly the lubrication effect.
 
ToddS ToddS I am happy to see you join the conversation. Is a bare flat strop at elevated angle sufficient to remove a foil burr or is there something special about a hanging strop?
 
There is no functional difference between a hanging strop and a flat strop. The curvature of the hanging strop is orders of magnitude larger than the curvature associated with convexity/microconvexity of the bevel - it simply plays no role in that.

The advantage of the hanging strop is that it allows you to find the angle by adjusting the tension on the strop and the downward force on the blade. This is particularly important for a straight razor as it allows us to increase the angle without raising the spine.

Very thin foils can easily flop back and forth without damage, so to remove those you need to bend them further down into the apex where they are thick enough to break.
 
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