Quantifying Sharpness
Using a Knife Sharpness Tester
Knife Sharpening Is Now a Measurable Process!
You Can't Improve What You Don't Measure!
Want Sharper Edges? Hair Shaving Sharp Edges? Me Too!! You should expect professional results from the Professional Knife Sharpening Service near you. Since I began making and sharpening custom knives, I'm most satisfied with the final edge I put on the blades. My system and tools give precise, repeatable results and shaving sharp edges. BUT, these edges have in the past been tested using anecdotal measurements. For example, "does it shave hair? How easily?" or "Will it slice phonebook paper? How smoothly?" I wanted an instrument that would permit "Quantifying Sharpness"!
This type of opinionated quality control doesn't sit well with me, a machinist who is accustomed to measuring features with instruments with .0001" (one ten-thousandth of an inch) resolution. No sharpness test produced a number against some scale, one that everyone could relate to. And since there was no finite measurement of knife sharpness, there was no process of Quality Assurance or Quality Control other than shaving a nearly naked arm and slicing paper. "How hard is this edge pulling the hair it shaves?" is an anecdotal result, not a number I can share with other folks and have them KNOW how sharp my (your) edges are. I had been searching to find something that could measure the sharpness of edges and put a NUMBER on that edge sharpness. Enter the new Edge On Up sharpness testers!
From the Edge on Up website: "The standard used to determine the sharpness of knives is called the BESS: Brubacher Edge Sharpness Scale. This scale was developed by Mike Brubacher, owner of Edge-On-Up. He has a background in sensor and test development in various industries. In 2012 he started developing a standard that could measure the sharpness of knives and needles. The result is the BESS standard that experts and enthusiasts quickly adopted as one of the most user-friendly methods to determine the sharpness of a knife."
This little instrument uses a certified and calibrated synthetic test medium, a "wire" (some calibrated plastic) similar to a heavy fishing line, and a weight scale with 1 gram of resolution. The knife is pushed gently into the test media being held by the sharpness tester until the edge severs the "wire". The instrument reads the force required to cut the wire in grams, and that is the BESS score. What's more, the BESS score correlates directly to the edge radius (yes, radius. No edge can be sharpened to a perfect apex). So if your sharpened edge rates 85 BESS, it tells you the edge radius of that blade is 85 nanometers (a human hair diameter is 60,000-100,000 nm, or .002-.004")
The BESS knife sharpness scale in the picture above gives comparative results. For example, a block between 250-350 on that scale is notated as "new high-end cutlery edges". Another block between 150-200 says "utility razor blade". Another roughly between 25-75 is noted as "double edge razor blades". The knife I carry every day for a "box opener" needs a touch up, it just checked 208. To check out a quick little video from "Sharpening Supplies" of how simple this instrument is to operate, just click HERE!
Measuring the actual sharpness, of sharpened knives on the BESS Scale helps me inspect, control and refine my sharpening process to the point where I'll be comfortable saying I'm delivering your custom kitchen knives that are as sharp as anyone in the country. Now, I know I'll never get to the 50 gram level of a razor blade, and you shouldn't want me to. There are a couple of reasons. One, knives are much thicker than razor blades, with far more obtuse primary and secondary bevels, and that negatively affects the force required to cut the media. Two, an edge as keen and sharp as a razor would not hold up well in the kitchen, in the sheath, on the cutting board, or in the pocket. I'm thinking the right place to be for kitchen knives will be around the 135-175 mark (VERY sharp utility razor range), and probably about 150-200 for hard use outdoor knives. (Incidentally, that knife in my pocket at 208, still shaves hair, but it pulls too much!)
I'm pleased to address knife sharpening again in the quest to improve quality overall. I settled on my sharpening system, stones, and strops early on in the shop setup. Since then I haven't really looked at it, because I was slicing phone book paper and comfortably shaving arm hair, and the process is by hand and FAST!! If Quantifying Sharpness gets us a few more points on the sharpness scale, I think we'll all be winners! To learn more about "How I Sharpen Your Knife", CLICK HERE!
To Make an Appointment for Knife Sharpening Near you, CLick Here!
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More FREE Learning:
Quantifying Sharpness Part III
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Thanks for reading,
Keith