please assist with 150 BESS score

[hardheart]

I received a PT50A just a few days ago, and have tested 8 knives with it so far. My best scores so far are a few of my kitchen knives, 100, 97, 98.

While I wish to improve those further, my primary issue is an 20CV folder. I have tested after sharpening 3 times and always get a score in the 150-158 range. My old CATRA goniometer shows a mildly convexed (freehand) edge around 18 dps. Over the last couple days I verified that with this edge I can clean shave arm hair in both directions, tree top arm hair against the grain, shave curls off of hair, push cut rolling paper along its length (but not on the short side), filet notebook paper, and dry shave stubble from my face with very mild skin irritation (no redness or blood weeping). After cleanly slicing notebook paper and push cutting rolling paper several times, the BESS worsened to 167. After that, I did 5 passes per side on crox followed by 10 per side on plain leather, and the score went back to 154. I have looked at the edge under a cheap pocket microscope that claims 100X magnification, and it looks pretty clean. Am I dealing with a burr? I thought the scores would get much worse after cutting if so. Is the ~10% increase in force indicative of a problem? All the references I see (primarily the knife deburring pdf I just purchased as well) say the BESS score would be much lower for the other cutting "tricks" I'm doing.

Typically, my rough grinding is done on a variety of things, diamond, SiC, etc, then 800 King or 1200 Sigma Power > 4000 King > 1.0 micron diamond on leather strop block or 13000 Sigma Power > 0.5 micron diamond on leather strop block > chromium oxide on leather strop block > plain horsebutt strop block. On the stones I generally scrub until there is a palpable burr, then do solely edge leading alternating strokes to remove. The strops are all of course edge trailing.

I have the full set of DMT diasharps from XXC to XXF, I'm thinking of using the 3 micron XXF then moving to the diamond strops. Should I expect better deburring and improved BESS scores? I don't use jigs, so I'm not sure how low a score I can get. I sharpen other knives (particularly fixed blades) around 13 dps +/- natural freehand deviation, but have kept the bevel width about the same as original on this 20CV folder.

[grepper]

Welcome to the forum hardheart!

Please consider that the following is just from my own experience…

Anything around 100 is very sharp. Congrats on those edges! Unless the goal is making razor blades, 100 is plenty, if not sharper than necessary. The thing to remember is that the sharper an edge is the thinner it is. 100 is extremely thin. It does not take much to dull it. A thinner edge is more susceptible to rolling and will dull more quickly. 150 or 200 works great for general use blades. Anything sharper will quickly change to that range with little use. That said, while the blade is still super sharp it’s cool.

Take a freshly sharpened blade that is ~100 and then chop a few carrots or potatoes, etc. Then measure the sharpness again That 100 edge does not last long.

It all depends on the use. If slicing sashimi with no blade to cutting board impact is the use, the sharpness will last a long time, but with anything with resistance or cutting board impact super sharp blades will dull 50-200 points very rapidly.

If a burr has formed after grinding from both sides and the burr is completely removed I would always suspect 80-150, with 150 being on the high side. From your description of how well you sharpen I would suspect burr.

When using a microscope, lighting is everything when it comes to visualizing a burr. Use a flashlight or other directional light. Move the light in all directions; from the top, edge on, spine to edge… every direction. It makes a huge difference. From some directions the burr can completely disappear. But when it’s right the burr will reflect light. Experiment with the direction of the lighting. It makes all the difference in the world.

Try dragging the edge at 45 or close to 90 degrees to the edge across the leather on both sides of the blade. This will bend the burr and hopefully fatigue it off. Then do it again at sharpening angle to straighten and clean things up.

For me at least a guided system works best. I’m not that good at freehand. I use a Kalamazoo 1SM and a Kallyrest. Generally edges turn out 100-120. But… chopping a few carrots and they soon turn 150 or more. Just depends on the blade.

I hate it when an edge does not get as sharp as is seems it should. Generally, IMHO, burr has been the reason.

Please keep us informed if you do/or do not figure it out!

[hardheart]

Thanks for the welcome, appreciate it.

While I never lost my interest in knives, I quit buying 15+ knives a year several years ago. Before that, I was sort of one of the 'darksiders' on BF as far as seeing how sharp I could get knives. Regrinds, test jigs on kitchen scales, trying most of the natural stones out there, up to getting test mules made and run on a CATRA for an experiment. I avoided the temptation of the BESS testers for years, but now I want to see if I can get back to where I was, and if where I was, was actually any good.

I still have several dozen knives, so I have many with more utilitarian edges and will readily resharpen on a smooth or mill file, coarse SiC stone, or sandpaper. But this little sharpening obsession creeps up now and again.

I will try your suggestion about dragging across the leather. Will also try to view from a few angles with the scope as well, though the dof is poor and the plastic lenses leave much to be desired. Might go ahead and replace the usb scope I got rid of years ago when I thought I was over this, lol.

[grepper]

"But this little sharpening obsession creeps up now and again."

Haha!  I totally understand that.  I was obsessed with sharpening for many years until I figured out what I needed to know.  I too think trying for the ultimate sharpness is fun, but now that I'm old a lazy I consider blades as tools.  100-150 is good enough for me. 

While it's fun, I've found that super sharp edges, and even 100-150 don't last that long for cutlery and general purpose blades.  Edges dull.  Since you have a PT50A, try it for yourself.  Get a blade really sharp and then chop some carrots or potatoes or even some kumquats and watch what happens.  Super sharp is ephemeral.

Super sharp is super cool while it lasts, but for me at least, the extra effort ain't worth it for general purpose blades and cutlery.  Test it for yourself.  It's a fun experiment.

The problem for me is that all the knives in my house are plenty sharp.  When I have not sharpened for a while I miss it and search through the knives in hopes of finding a blade that hints at needing sharpening.  Most of the time I leave saddened and unfilled.  

I prefer a toothy edge because I've found they work best.  For 99% of cutlery, I use a super simple sharpening method:  Kally 1SM+ Kallyrest with a 150 grit Cubitron belt.  Depending on the burr, deburr wth very fine Scotch-Brite belt.  Always finish with the rough side of plain leather belt with no compound.  Edges always seem to pop out 100-130 and nice and toothy.

When I first decided to figure out sharpening I got suckered by all the literature into thinking there was some secret to sharpening.  Some secret equipment.  Secret Zen Master knowledge, secret Zen super sharpening dust, deburring with secret camel butt leather etc.  But after a lot of work, and $$$ spent, in the end I discovered the real secret... Make as small a burr as possible and remove it.  That's the big secret. 

Lots of different equipment will do a fine job of grinding an edge.  The main difference between sharpening methods I've found is efficiency and speed of getting the job done.  For me, sharpening is fun and rewarding but I don't want to spend an hour on a blade.  After trying stones on sticks, paper wheels, water wheels and by hand stones, etc., I ended up with belts and a guided sharpening rest.  Fast, effective, extremely versatile and super inexpensive for different grit belts.

This is just me but... The 'Net promotes way overthinking sharpening.  Make a tiny burr and remove it.  However you want. 

The hardest part is burr removal and understanding burrs.  Once a burr is created by grinding from both sides and it is removed the edge will be sharp.  The smaller the burr the better.  Once a burr is created additional grinding is detrimental. 

Maybe you will enjoy this post:
http://bessex.com/forum/showthread.php?t...41#pid4341

[hardheart]

Dragging some leather at ~45 degrees appears to have helped. Followed that by a few passes on the 0.5 diamond and got 103.

[grepper]

Outstanding. Sure sounds like there was still some remaining burr and you got it removed. 103 is nice and sharp.