Sharper than a razor. What does that actually mean? For years, woodworkers, chefs, and knife nerds relied on the "thumbnail test" or shaving arm hair to see if a blade was ready. It’s subjective. It’s messy. Honestly, it’s kinda dangerous if you’re tired and your hand slips. That's where the Edge on Up sharpness tester changed the game by turning a "feeling" into a hard number.
I remember the first time I used a BESS-certified tester. I had a chef's knife that I thought was screaming sharp. I’d spent twenty minutes on a 6000-grit waterstone. It felt smooth. It sliced paper like butter. Then I put it on the test medium. The number flashed: 245. I was crushed. In the world of Edge on Up, 245 is "utility razor" territory. It wasn't even close to the "high-end cutlery" range I was aiming for.
That’s the thing about this tech. It doesn't care about your ego or how much you spent on your stones. It measures the force in grams required to cut through a specific, standardized synthetic filament.
The BESS Standard: Not Just a Random Number
You’ve probably seen the term BESS everywhere if you’ve looked into these machines. It stands for Brubacher Edge Sharpness Scale. Mike Brubacher, the brain behind Edge on Up, realized that the industry lacked a universal language for sharpness.
Without a scale, "sharp" is just an opinion.
The scale generally runs from 0 to 2000. A double-edge razor blade sits somewhere around 50. A butter knife? You're looking at 2000+. Most people aiming for a high-performance kitchen edge want to see something under 200. If you hit 150, you're doing great. If you hit 300, you’ve got work to do.
The mechanism is deceptively simple. You have a base unit with a load cell. You bridge a piece of certified test filament over a small gap. You lower your blade onto that filament. The sensor records the peak weight at the exact millisecond the filament snaps.
It’s precise.
Why Your "Paper Test" is Failing You
We’ve all done it. You grab a piece of notebook paper or a phone book page (back when those existed) and slice. If it doesn't snag, it's sharp, right? Well, sort of. Paper is a composite material. It has fibers, glues, and varying thickness. You can cheat a paper test by changing the angle of the slice or the speed of your hand.
The Edge on Up sharpness tester eliminates the "human flick."
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Because the machine measures downward pressure—not a slicing motion—it reveals the true geometry of the apex. If you have a wire edge or a burr that’s just folded over, a paper test might still feel okay. But the BESS tester will catch it. The filament won't break cleanly, or it will require significantly more force because the edge is technically "rounded" by that tiny flap of metal.
Different Models for Different Needs
Edge on Up doesn't just make one box. They have a lineup that scales depending on how much of a data nerd you are.
The Edge on Up Industrial (EUA) is the workhorse. It’s built for heavy use, often seen in professional sharpening shops or manufacturing plants. It samples at a high rate, meaning it’s very accurate at catching that peak force moment.
Then there’s the Log 2000. This one is great because it can actually talk to your computer. You can plot graphs. Why would you want a graph of a knife cut? Because it shows the "crush" before the "cut." For researchers or serious custom knifemakers, that data is gold.
Most hobbyists end up with the Edge on Up PT50 series. It’s portable. It’s battery-operated. It fits on a cluttered workbench without being a nuisance.
Honestly, the "best" one is whichever one you will actually use. If you have to spend ten minutes setting it up, you'll go back to the thumbnail test. The PT50A is usually the sweet spot for most guys.
The Secret Variable: The Test Filament
Here is something people get wrong all the time: you can't just use fishing line.
I’ve seen guys on forums trying to "calibrate" their machines with 4lb test monofilament. Don't do it. The BESS filament is a very specific, synthetic material designed to have zero "give" and a consistent breaking point. If you use a different medium, your numbers are meaningless. You can’t compare your 300 to someone else’s 300.
The filament comes in two main types: the clips and the rolls.
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- The Clips: These are pre-tensioned. You just slide them into the holder. They are incredibly consistent but cost more per test.
- The Roll: This is a spool of filament you tension yourself using a weighted fixture. It’s way cheaper in the long run. If you're testing twenty knives a day, get the roll.
Understanding the "Burr" Trap
One of the most enlightening things about owning an Edge on Up sharpness tester is learning about the ghost burr.
You sharpen a knife. It feels incredible. You test it: 160 BESS. Amazing.
Then you slice one piece of cardboard and test it again.
Suddenly, it's 450 BESS.
What happened? You didn't dull the steel on one piece of cardboard. What you actually had was a "wire edge"—a microscopic ribbon of metal that was perfectly aligned but not structurally sound. The first test cut through it, or the cardboard ripped it off, revealing the true, blunter edge underneath.
Without the tester, you’d go to work with that knife and wonder why it felt "off" after five minutes. With the tester, you realize your deburring process needs work. You realize you need to spend more time on your leather strop or your ultra-fine ceramic.
Nuance in the Numbers
Don't get obsessed with getting to 0. It’s impossible, and frankly, a 50 BESS edge on a camping knife is a bad idea. It’ll chip the second it hits a knot in a piece of wood.
Sharpness is a trade-off with durability.
- 150-250: Ideal for high-end kitchen knives.
- 300-400: Perfect for an Every Day Carry (EDC) pocket knife.
- 400-600: Where most factory knives (even expensive ones) land out of the box.
If you get a brand new $300 pocket knife and it tests at 550, don't be surprised. Manufacturers often prioritize a "toothy" edge that feels sharp to a thumb but isn't actually refined.
Real-World Application: The Professional Sharper
If you run a sharpening business, an Edge on Up sharpness tester is basically a marketing machine.
Think about it. A customer brings in a dull pile of Henckels. You test them in front of the customer. "These are at 800 BESS, basically a spatula."
You sharpen them. You test them again. "Now they’re at 180."
You’ve just given the customer empirical, scientific proof of the value you provided. You aren't just a guy with a grinder; you're a technician. It builds immediate trust. Plus, it helps you catch mistakes before the customer gets home. If one knife in a set comes up at 350 while the others are 150, you know you missed a step on that specific blade.
Limitations and Human Error
The machine isn't magic. It's a scale.
If you "slam" the knife down onto the filament, the impact force will spike the reading. You have to be steady. Slow. Imagine you’re trying to cut a hair without moving it.
The angle matters too. If you tilt the knife, you're increasing the surface area of the cut, which increases the force required. You have to keep the blade perfectly vertical. Most Edge on Up testers come with a fulcrum or a guide to help with this, but it still takes a bit of practice to get "repeatable" results.
If you test the same spot on a blade three times and get 200, 205, and 198, you're doing it right. If you get 200, 450, and 120, you need to work on your technique.
Actionable Steps for New Users
So, you just unboxed your tester. What now?
First, calibrate it. Most units come with a calibration weight. Use it. Every time. Don't assume it stayed accurate in the box.
Second, test a control. Grab a fresh, brand-new utility razor blade (the kind for a box cutter). It should consistently hit between 150 and 200. This confirms your machine and your technique are in the right ballpark.
Third, map your edges. Don't just test the middle of the knife. Test the heel, the belly, and the tip. Usually, people are great at sharpening the belly but neglect the last inch near the handle or the very tip. The tester will expose those weak spots immediately.
Finally, keep a log. Whether it’s in a notebook or the Edge on Up software, track your progress. You’ll start to see patterns. You might realize that your 1000-grit diamond plate actually produces a better "working edge" than your 8000-grit waterstone for certain steels.
The Edge on Up sharpness tester isn't just a gadget. It's a teacher. It forces you to be honest about your skills and gives you the data you need to actually get better. Stop guessing if your knives are sharp. Know they are.
Next Steps for Accuracy
To get the most out of your testing, ensure your test medium is stored in a cool, dry place, as extreme humidity can slightly affect the tension of the synthetic filament. Always wipe your blade with a microfiber cloth before testing to remove any residual honing oil or metal dust that could cause a "slip" on the filament, resulting in a false low reading.