In Dual Grit Sharpening, you sharpen the first side of the edge with a coarse stone, and work the second side of the edge up to a fine stone, leaving the 2 edge finishes combined at the apex. Usually, the edge forms best using all edge-trailing strokes, and some stropping is often required to clean up the edge from unhelpful amounts of burr.
My Preferred Sharpening Gear for Dual Grit Edges at the time of this entry are:
- Coarse Side - 250-400 grit CBN or Diamond plate (e.g. Spyderco, or DMT) for high aggression, though Norton Crystolon Coarse (SiC) works well too, especially for more conventional/lower carbon steel, or thinner edges
- Fine Side - Soft water-stone (using SueHiro Cerax 3K atm, also good results from King 6K) OR fine resin-bonded/OCB diamond water-stone (e.g. Venev) on steel with more than 3% Vanadium)
- Strop - I do 3-10 strokes on flat denim loaded with Mother's Mag & Aluminum polish for low-mid Vanadium steels, and 30+ light strokes of fine (sub 1 micron) diamond on flat leather for high Vanadium Steel
- Note: I have also had very good aggression results from UltraFine Ceramics (Spyderco, Fallkniven) on fine side of edge, but these seem to require a little more stropping to remove fine feather-burr
The sharpening method seems to extend working-edge functionality and aggression significantly (the most outstanding test result to date being a roughly 50% increase in wear resistance in Pete's CPM MagnaCut test - link in thread). However, as all things are a trade-off, it seems that this long lasting aggression may come at a cost of slightly reduced push-cutting/shaving efficiency and a slightly less durable apex for impact tasks (at least in my testing so far).
The most up-to-date picture of my sharpening method right now is also linked in thread if you want more specifics, and I am working with the folks at Spyderco to conduct testing on a range of different steels in an effort to find sharpening protocols that are optimized for each specific category of steel, and perhaps some specific steels that benefit from one particular method, stone, or abrasive combination.
I have created this topic to offer what knowledge I have to anyone on the forum, and I am most happy to respond to questions (sharing what I do and don't know).
This is a place for people to share their experiences, ideas, and questions - so that I/we can troubleshoot how to get the longest possible life out of your knife edges for the least work.
Fire at will...