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"!
I have a problem with the way knife sharpness is traditionally tested. Shaving hair or slicing paper only answers a "yes" or "no" quality question. As a machinist, I'm used to being able to measure features with instruments that have a resolution of one ten-thousandth of an inch or less. Unfortunately, there's been no such thing as a standard measurement for knife sharpness that everyone can relate to. This means that there's no real way to ensure the quality of a knife's sharpness beyond simply testing it by shaving a nearly naked arm or slicing paper. While this may give you an idea of how sharp the knife is, it's not a quantifiable measurement that you can share with others. That's why I was excited to discover the Edge On Up sharpness testers. The company uses a standard called the Brubacher Edge Sharpness Scale (BESS) to measure the sharpness of knives. The BESS was developed by Mike Brubacher, the owner of Edge-On-Up, and has become one of the most user-friendly methods for determining 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 think 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!
More FREE Learning:
Quantifying Sharpness Part III
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Thanks for reading,
Keith