How do you sharpen for the best BESS score?

[Twindog]

The theory is that the force to initiate the cut is greater than the force to complete the cut, so the goal is to penetrate a few microns, or maybe tens of microns and then the fibre cleaves. ...

Just thinking out loud.

So if it's the initiating of the cut that is most important, it would seem that a fairly coarse and very acute edge -- say 10 degrees inclusive sharpened with 400-grit diamonds and followed by polishing the edge with high-grit stones (5,000 grit plus) and then stropped with .25 diamonds would be a good strategy.

The coarse edge would contain a lot of very sharp teeth that might initiate the cut easily -- like it's easier to push a pointy knife tip into a tomato than it is to push cut into the tomato with with the edge.

It doesn't seem like the edge width at the shoulders (BTE) would help much, but the angle of the edge would. And I'd guess that the sharpness of the apex would be more important than the angle.

 

[HeavyHanded]

Just thinking out loud.

So if it's the initiating of the cut that is most important, it would seem that a fairly coarse and very acute edge -- say 10 degrees inclusive sharpened with 400-grit diamonds and followed by polishing the edge with high-grit stones (5,000 grit plus) and then stropped with .25 diamonds would be a good strategy.

The coarse edge would contain a lot of very sharp teeth that might initiate the cut easily -- like it's easier to push a pointy knife tip into a tomato than it is to push cut into the tomato with with the edge.

It doesn't seem like the edge width at the shoulders (BTE) would help much, but the angle of the edge would. And I'd guess that the sharpness of the apex would be more important than the angle.

IIRC, closeups of the cut ends showed imprints in the media from scratch pattern/edge irregularity almost all the way through.
Only the last 10-20% snapped clean.

 

[ToddS]

IIRC, closeups of the cut ends showed imprints in the media from scratch pattern/edge irregularity almost all the way through.
Only the last 10-20% snapped clean.

Yes, that's why I described it as "the theory."

 

[Natlek]

IIRC, closeups of the cut ends showed imprints in the media from scratch pattern/edge irregularity almost all the way through.
Only the last 10-20% snapped clean.

That scratch pattern should help to get better score on test ? I mean on less contact/friction with media ?

 

[Glenn Goodlett]

Dude (Deadboxhero) already said the test media will be pulled taught to 100 grams of force as measured with a spring scale.

Seems like one would need to use the pivot thingy so as not to introduce a draw to the cut.

The best I ever got was about 100 BESS but that is with a knife I actually use at 18 dps.

You guys that get 40 and below have some deal with the devil or something. That's like magic to me.

 

[000Robert]

Dude (Deadboxhero) already said the test media will be pulled taught to 100 grams of force as measured with a spring scale.

Seems like one would need to use the pivot thingy so as not to introduce a draw to the cut.

The best I ever got was about 100 BESS but that is with a knife I actually use at 18 dps.

You guys that get 40 and below have some deal with the devil or something. That's like magic to me.

According to their instructions, you just pull the test media until it is straight with no sagging inside the cutout for it. Then snug the nut up. That's it! It's actually pretty simple.

 

[000Robert]

IIRC, closeups of the cut ends showed imprints in the media from scratch pattern/edge irregularity almost all the way through.
Only the last 10-20% snapped clean.

I don't see any "snapping" in the photo that I took a while ago except for maybe right at the bottom edge. I need to get a better camera.

 

[HeavyHanded]

Yes, that's why I described it as "the theory."

Also, the original test media had no spec'd tension or means of reliably loading it. Pre-loading will def increase the snap effect.

The pics did show (IIRC, really need to find the thread that had the micrographs) what looked like jacket material...

 

[HeavyHanded]

That scratch pattern should help to get better score on test ? I mean on less contact/friction with media ?

You'd think any irregularity would increase friction. There might be a beneficial trade-off when it comes to initial penetration, but the contact area is mighty small to begin with. Personally I didn't have good luck with coarse edges - good scores started at about a 600 grit finish.

 

[ToddS]

Also, the original test media had no spec'd tension or means of reliably loading it. Pre-loading will def increase the snap effect.

The pics did show (IIRC, really need to find the thread that had the micrographs) what looked like jacket material...

Don't bother, I deleted those micrographs when EOU declined to work with me.
There is a cladding layer, but it didn't appear to cut any differently from the core.
It was very obvious from those micrographs that the blade penetrated by repeated stop-start motion, but that may be a result of the prototype design having it sit right at the critical force between adding weights. I don't think you can apply force that slowly/carefully with the production version.

 

[HeavyHanded]

Don't bother, I deleted those micrographs when EOU declined to work with me.
There is a cladding layer, but it didn't appear to cut any differently from the core.
It was very obvious from those micrographs that the blade penetrated by repeated stop-start motion, but that may be a result of the prototype design having it sit right at the critical force between adding weights. I don't think you can apply force that slowly/carefully with the production version.

Now that you mention it I do recall there being a chatter effect to many of the cuts, as well as evidence of twist tension being released.

 

[Diemaker]

Don't bother, I deleted those micrographs when EOU declined to work with me.
There is a cladding layer, but it didn't appear to cut any differently from the core.
It was very obvious from those micrographs that the blade penetrated by repeated stop-start motion, but that may be a result of the prototype design having it sit right at the critical force between adding weights. I don't think you can apply force that slowly/carefully with the production version.

Everything really makes it sound like the test media is Plastic Optical Fiber. Mention of a cladding really narrows it down. How many fibers like this have a cladding? I know POF does. I would bet the start-stop motion was all in the fiber and not the cutter, think of the mass difference for acceleration-deceleration. I would also bet that the highest force needed for the cut would be at the initiation.

I expect this fiber to be sensitive to notching, especially if it is under tension. So the best scrore will be with the keenest edge possible.

 

[000Robert]

Also, the original test media had no spec'd tension or means of reliably loading it. Pre-loading will def increase the snap effect.

The pics did show (IIRC, really need to find the thread that had the micrographs) what looked like jacket material...

The BESS test media looks to me like a single strand of black polymer of some sort. And it is not supposed to be under tension. You only put enough tension on it to keep it straight in the groove, which takes nearly nothing. Putting 100g of tension on it is not the way you are supposed to tension it.