Stropping Angles

[Josh]

Now we’re doing requests… I’d be really interested what happened if you stropped a clean edge with a plain, unloaded, strop.

Yeah mark I remember the same…. It didn’t do anything. Dr. Verhoeven also showed in his paper that it basically had no effect.

– Josh

[Zamfir]

Thanks Clay!

Have you done this same testing before with balsa strops used the same way as you are using the leather for this test?

[tcmeyer]

Clay:

This investigation has got my curiosity peaked because of a recent experience. I ordered a Rikon 6X48 belt sander with a 10″ disc sander from Klingspor. When it arrived, the UPS guy dropped it in my garage and I was stumped with figuring out how to get it into the house, which was three stairs higher. It weighed about 110 lb and I’m almost 70 y/o with a 30 lb limit for my back. No heap-strong neighbors or relatives at hand. So I arranged my come-along to lift it up, but I had to pull it into the doorway under tension. With everything under strain, I reached into my pocket for my very-sharp Spydie. When I touched the 3/8″ nylon braided rope, the rope seemed to explode and the parcel dropped conveniently onto the threshold. There was absolutely no effort to cut the rope. It just parted instantly. Immediately, I began to wonder what the effect of tension was on the ease of cutting in a cord. What’s the greater variable? Tension or sharpness?

Frankly, I’ve not paid attention to your testing of sharpness, so I’m kind of sticking my nose into the mix here and won’t mind if you choose to ignore me. I don’t know the history of choosing the cord you’re testing against or the method, but I would have recommended a more homogeneous (read invariable) material and gone more in the direction of Rockwell hardness testing. Perhaps a homogeneous media like a soft plastic – maybe a high tensile strength monofilament. Choose a standard profile (like maybe 1/8″ in diameter) then measure the depth of penetration given a fixed amount of force applied. For toothy quality, do the same thing, but traverse the edge some fixed distance, as with your existing apparatus. Maybe a hi-res digital dial indicator could measure the depth of cut. As with the Rockwell scale, you might have different classes (diameters of monofilament) for an increased range of measurements.

If I’m correct in inferring from your video here that your current method requires that you fiddle with the controls while the test progresses, this is an additional variable to skew your results. The depth of cut method is the equivalent of lowering the tone arm onto your LP turntable.

For the existing apparatus, I suggest you find an appropriate coil spring. Coil springs generally have a known force to extend a known distance. Tie one end to your clamp assembly, then tie your cord to the other end and turn the knob on your clamp assembly to pull the spring/cord to the point where the spring is extended the known distance, at which point you will know that the cord is under a standard tensile force. This would be a repeatable condition and save you the need to measure it each time. Maybe measure the force to part one of the no-stretch fishing lines. Using “SpiderWire” would be an interesting twist.

Meanwhile, I’m curious about the same effect with diamond film on glass, as I’ve seen some rounding there too, but on a much lower level. The fact is that film on glass is not perfectly flat and hard. It too has some degree of compressibility. Maybe we could establish that film needs to be set back some amount too.

Now that I’ve pooped on your porch, let me say that the open discussions here are absolutely delightful. The contributors to this forum are absolute gentlemen and the sense is that we’re sharing in ground-breaking research as it’s happening. I don’t know of any other forum where people like us have that sort of opportunity. Class attracts class and I can’t thank you enough for that and for your openness to outside ideas.

[Mark76]

Zamfir, in the past I have carried out experiments with leather/balsa strops and the WE pastes (and other pastes). I found that balsa + paste works about as well as balsa + leather with regard to abrasion and “adhesive based wear”.

(Thanks Cliff, after all the discussions in the past about the definitions of stiction, burnishing etc. you seem to have provided us a proper name for the effect.)

Leather of course has more give to it and therefore works better for, e.g. convexing an edge. And the use of balsa with diamond stuff < 0.5 micron is sometimes advised against, since diamond particles this small might disappear in the crevices of the balsa. But I never tested that.

You can read about my experiments (with far lesser pics than Clay's): http://moleculepolishing.wordpress.com/category/stropping/

Molecule Polishing: my blog about sharpening with the Wicked Edge

[Gib Curry]

Interesting topic… must be important, eh?

I was curious to see what other threads piled up so many replies so quickly.

“Geometry and Kinematics of Guided-Rod Sharpeners” and “Super-polished Edges” are the other two biggies I found.

You are all so OCD, I love it.

~~~~
For Now,

Gib

Φ

"Everyday edge for the bevel headed"

"Things work out best for those who make the best out of the way things work out."

[Zamfir]

Zamfir, in the past I have carried out experiments with leather/balsa strops and the WE pastes (and other pastes). I found that balsa + paste works about as well as balsa + leather with regard to abrasion and “adhesive based wear”.

(Thanks Cliff, after all the discussions in the past about the definitions of stiction, burnishing etc. you seem to have provided us a proper name for the effect.)

Leather of course has more give to it and therefore works better for, e.g. convexing an edge. And the use of balsa with diamond stuff < 0.5 micron is sometimes advised against, since diamond particles this small might disappear in the crevices of the balsa. But I never tested that.

You can read about my experiments (with far lesser pics than Clay's): http://moleculepolishing.wordpress.com/category/stropping/%5B/quote%5D

Great articles! Those are very helpful.
What I am curious about is the effect of the angle with balsa just like Clay is showing here with the cow leather. Will the balsa convex the edge less?

What I am thinking is that if you are sharpening a knife for edc where you would normally put on a micro bevel to give the edge more durability, maybe you just sharpen it all up and keep the leather at the same angle and that automatically gives you the 2 deg more angle to give you that enhanced the durability of the edge?

Or am I totally missing the idea of the micro bevel?

From what I am understanding the main reason is to have the increased angle for more durability. Another reason would be to give it a toothy edge for specific tasks which would not be accomplished by the leather or balsa and paste.

This thread is showing the effects of the different angles in respect to the main sharpening angle using the plates first. Depending on the hardness of the material and pressure used, you would get different end angle results. I would guess that the microfiber strop, vs kangaroo, vs cow, vs balsa would all have slightly different effects. It is awesome to actually see the effects in the way Clay is able to photograph the edge cross section. That is huge in my mind in understanding what is going on.

[wickededge]

Tom,

Those are great questions and thoughts, especially about the cordage to use. I haven’t really done much with testing sharpness for draw cutting on this jig yet, was just replying to Cliff and checking the feasibility of converting the point sharpness testing machine to work with draw cutting. Normally I don’t have to juggle so much when testing, it was just awkward trying to manage the camera and fiddle with the bits I’d rigged up to see if they would work. As it’s set up now for point sharpness testing, it’s very straight forward and the material I use is ubiquitous and consistent. It’s a specific brand of Scotch tape by 3M that BassLakeDan had promoted so that we’d all be comparing apples to apples. If I can adapt the jig for draw cutting, I’ll definitely find a very consistent product as a test media. In the video, I just grabbed the only piece of string I had handy at the moment. For the tension on the string/rope, I’m pretty sure I can rig a spool on one side of the clamp that feeds across the collar, through a hole in the other side of the clamp and out to where I can attach a fixed weight so that the tension is constant. I’m imagining an alligator clip with a weight attached. It should make reloading the media after each test pretty easy. Mono-filament is a good thought. BassLakeDan was also promoting it a choice so we could all use the same thing and check each other’s results.

-Clay

[wickededge]

Zamfir – I’ll work on some tests with balsa this coming week.

-Clay

[Mark76]

Zamfir, you’ve joined this forum at a pretty nice time, when we’re experimenting with things like microbevels and stropping with heavy pressure.

But please don’t get the impression that most people do this on a regular basis. I think most WEPS users don’t apply microbevels at all and, if they strop, they do light stropping. So do I most of the time. (Althrough I do apply microbevels to some of my Japanese kitchen knives.) So when you’re starting to learn sharpening with the WEPS, I’d probably ignore these more advanced topics for a while. (In applying them, not reading about them, of course.)

Just my 2 c to set the expectations.

Molecule Polishing: my blog about sharpening with the Wicked Edge

[Zamfir]

Yeah no kidding Mark!

Thanks a ton Clay! I have now stropped with balsa and cow. It seemed way easier to get a good distribution of diamond paste on the balsa and the feedback while using it seems much better right off the bat than the leather. So I am hoping the results are good with balsa.

Seems like I always have to fiddle with the leather and add more paste to get it to have the suction like the balsa did right away and have not needed to add any more paste.

After my first experience with a microbevel on my edc I have decided to wait a while until I have better form and the stones are more broke in and I know more about them. Each knife I sharpen gets better. This last time I stropped my EDC with the 1 and .5 balsa and It seemed the sharpest it has ever been. push cut for sure.. hair popping..nope. So I looked at it with the usb scope…still a little toothy microbevel left..I mean you can barely see it but the edge is not smooth. I am going to keep sharpening and reading. Thanks guys! I am soo geeking out on sharpening now. I am going to pull out all my hunting knives and “fix” them all. Someday maybe I will get the hair popping thing down.

[Gib Curry]

Yeah no kidding……….I am going to keep sharpening and reading. Thanks guys! I am soo geeking out on sharpening now. I am going to pull out all my hunting knives and “fix” them all. Someday maybe I will get the hair popping thing down.

I’ve had my WE for over a year now. My understanding still exceeds my ability…. maybe far exceeds my abilities.

But every blade is better….

Even though my brain hurts, just gotta love the conversation….

“geeking out”…. exactly….

~~~~
For Now,

Gib

Φ

"Everyday edge for the bevel headed"

"Things work out best for those who make the best out of the way things work out."

[wickededge]

Seems like I always have to fiddle with the leather and add more paste to get it to have the suction like the balsa did right away and have not needed to add any more paste.

You might try moistening the leather before use. I really like rubbing alcohol applied via a spray bottle. It helps with the ‘stiction’. It’s also great to use when you’re applying the paste because it loosens up the paste itself, allowing better distribution and it also helps it to soak into the leather so that it doesn’t just scrape off when you’re using the strops.

-Clay

[wickededge]

Back at it again today…

I reprofiled the edge to 20 dps with the 1000# diamond plates, then stropped very lightly, just 10 strokes per side with the 14um diamond on cow leather strops, also at 20 dps. Here is the photo after stropping:

20 dps using 14um diamond and cow leather strops – very light pressure, 10 strokes per side

There is still some angle change, mostly right at the very edge. There was a very small loss in sharpness after stropping as well:

1000# 20 dps: 310
14um 20 dps: 328

It’s not much difference so my initial thought is that stropping at angle, even lightly isn’t beneficial and may be even slightly counterproductive. I’d have to do a lot more repetitions of the same test and ask others to repeat it as well before calling it a conclusion though. Another factor could be the grit which I’m using to strop. A finer grit might yield different results…

For now, I’ll move on to testing the balsa strops at angle and below angle.

*An interesting side note is that the point sharpness of the edge after the 1000# diamond plates got progressively worse with each re-profiling. I don’t believe it was sharpening technique causing the issue though I can’t be 100% sure. I was very careful but I wasn’t as diligent about keeping the plates clean. When I re-profile the blade for the balsa tests, I’ll clean the plates thoroughly. My guess though is that there is blade wear with each sharpening and I’m getting into progressively thicker portions of the blade. It may be that I’ll need to thin the blade soon.

Attachments:

• 20dps14um10lightstrokes.jpg

-Clay

[Ronald Cindia]

I seem to check this thread a couple times a day for an update. I guess that means I have a sharpening addiction!

[wickededge]

I seem to check this thread a couple times a day for an update. I guess that means I have a sharpening addiction!

Hopefully I’ll do more on it tomorrow. If not, then on Monday. 🙂

-Clay

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