Scanning Electron Microscope Images for Our Sharpening Protocols

Size: px

Start display at page:

Download "Scanning Electron Microscope Images for Our Sharpening Protocols"

Isabel Lucas
5 years ago
Views:

1 Knife grinders Scanning Electron Microscope Images for Our Sharpening Protocols SEM images are by courtesy of Todd Simpson. We use two main lines of sharpening protocols: blades of certain types of steel we do on Japanese wheels; and others on CBN wheels. Our typical sharpening routine is to set edge and shape bevel edge-leading on a grit #1000 wheel, then refine the edge on a sequence of paper wheels with progressively finer diamonds. By SEM data, there is a great difference in the edge formation along these two lines of sharpening. JAPANESE WHEELS The JIS grit 800 (ISO/FEPA 1200) Japanese wheel produces an edge width in the range of 0.5 micron, narrow and resembling isosceles triangle with little or no convexity of the bevel near the apex. There is significant variation in the apex width along the edge. Edge-on view image of the edge set on a Japanese stone, JIS grit

2 Focused Ion Beam (FIB) cross-section image of the same edge 2

3 CBN WHEELS The grit 1000 (ISO/FEPA) CBN wheel produces an edge width in the range of 0.1 micron with pronounced convexity of the bevel near the apex. Similarly to Japanese wheels, there is significant variation in the apex width along the edge. Edge-on view image of the edge set on a diamond plate, grit 1000 (ISO/FEPA) Focused Ion Beam (FIB) cross-section image of the same edge 3

4 This difference effects the way we refine edge on paper wheels with diamond paste in the next step of our sharpening protocol. After the Japanese wheel we hone at +0.4 degree more than the edge angle to sharpen the apex further (e.g. the edge that we set at 15 degree per side on the Japanese wheel will be honed at 15.4 degree). After the CBN wheel we hone at -0.1 degree less than the edge angle to narrow the edge on the sides by reducing convexity near the apex (e.g. the edge that we set at 15 degree per side on the CBN wheel will be honed at 14.9 degree). Having improved our sharpening protocols based on SEM data studies, we now steadily get the same or better edge sharpness as the best DE safety razors. For quality mainstream steel, from Global and up, the edge sharpness is BESS or near 0.05 micron edge apex width. For premium high-end steel, the edge sharpness is BESS or under 0.05 micron edge apex width. An edge that sharp easily passes the best hanging hair tests, and the Tally-Ho cigarette rolling paper held horizontally cross push-cut test. A priory we thought coarser grits give a thicker edge, and the purpose of working the edge through progressively finer grits is to thin the edge to make it sharper. That turned out to be an errancy. Having studied through the Todd S SEM images, it dawned upon us that the edge often well below 0.1 micron is already there even after a 300 grit stone, for sure after grit # micron is a DE safety razor edge as we know. For the 300 grit it depends on other variables, but for the CBN/Diamond #1000 edge-leading invariably. In knife sharpening we raise an even burr all along the edge to make sure that the sides of the edge have met at the apex, and now we know that the edge apex is sharp right at the burr base. Below is SEM image of a cross-section cut into the edge through the honed burr. 4

If having deburred we get an edge duller than 50 BESS, it means we've rounded the edge and worsened the initial sharpness hidden behind the burr.

5 Our desired sharpness is already there, we only have to deburr completely without rounding the very apex, and expose that 0.1 micron edge that already is there. Sharpening knives is all about deburring. If having deburred we get an edge duller than 50 BESS, it means we've rounded the edge and worsened the initial sharpness hidden behind the burr. As this became clear, the very first trial of honing off the burr at -0.1 degree less than the edge angle to spare the very apex, gave 50 BESS i.e 0.1 micron DE razor edge, and proved the concept. The rest is history. Perfect edge 5

Kota Japan Finest Edge Knife Sharpening Guide

Kota Japan Finest Edge Knife Sharpening Guide Introduction A sharp knife is a joy to work with but it is very scarce in many kitchens. When you buy a new knife, you will notice that it loses its sharpness