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Jon Magill wrote a really great article for the Spring 2008 edition (Vol 23, #1) of AAW's "American Woodturner". In the article titled, Build an Overhead Drive (pages 30-31), he wrote: Cutters must be sharp! You will never achieve a reflective cut off the tool, which is always the goal in OT, if your cutter is not sharp. I once read that you can never get a better finish off of your tool than the finish on the tool itself. In other words, unless your cutter has a mirror finish, you cannot expect to produce a mirror finish on your work.
With regards to sharpening, the method outlined by J.H. Evans in Ornamental Turning, Chapter VI (1903) is:
Oilstone Powder is very hard to find these days. One can find it occasionly on eBay or other similar sites, but similar products are available from clockmaker suppliers. One which offers such powders is Ernst Westphal. I have not done any testing with ornamental tools, but products like Kent Grit Diamond Lapping Paste Polishing Compounds should be usable. They are oil based and come in grits from 40 microns, all the way down to 0.25 microns. When used with paper wheels on a grinder, they are very effective for polishing knife edges to be better than razor sharp. Another source of guidance is Turning and Mechanical Manipulation, Vol. 3 by Charles Holtzapffel, chapter XXXII (1850). The Sharpening Handbook is intended to also be a good resouce for data about sharpening fly cutters. There is information on both round rod cutters, and traditional cutters. This site is especially useful if you are looking to use a Tormek grinder. The Accu-Finish machine has been used for years by machinists, and is also used by some ornamental turners. These machines use diamond wheels, or a ceramic lapping wheel with a diamond spray. This is a really great machine, especially as it has a built-in goniostat, but it can be a bit expensive. The video to the left shows a demonstration of one that was given at the 2018 Ornamental Turners International Symposium. I've found the Tormek grinder to meet my needs, though I did have to make some of my own jigs. |