A CBN conical hone, supplied as a blade only, tapering from 19 to 9mm diameter. Blade length is 152mm. The CBN abrasive is a fine grit (Grade D25, equivalent to approximately 600 grit in conventional grit sizes). The blade is of pressed steel and of approimately semi-circular cross-section.
Producers of grinding wheels and special tooling using CBN abrasives to give youir tools the finish they deserve in the shortest time possible.
Although we in the woodworking "industry" have done much to improve the performance of our sharpening systems over the years, especially in regard to the grinding wheels which we use (remember when folk tried to sharpen HSS on grey wheels!!), there has been little in the way of change in the fundamentals of the abrasive grinding materials we use. A introduction into the market by Diamet & The ToolPost a few years ago changed that, calling upon expertise which has been in the domain of engineering manufacturing but which remained unattainably pricey for non-industrial use until now.
That development is the use of CBN grinding wheels. CBN grinding wheel for sharpening of woodturning tools.
What is CBN? The acronym "CBN" (a trade mark of General Electric Corp.) stands for Cubic Boron Nitride: a ceramic grain almost equalling diamond in hardness but which can be used for sharpening High Speed Steel (the material of which most turning tools are now made). The suitability of CBN for grinding HSS is important because, despite attempts to use it, diamond is not a suitable abrasive grain to use when grinding tools on a high speed dry wheel as it affects the steel at relatively low temperatures - well within the range of temperature achieved when grinding, even briefly. These outstanding wheels, which have an almost indefinite life if treated with respect, are used in place of a normal granular wheel on a 6" or 8" high speed grinder.
Thanks to the nature of the bonding between the CBN grains and the supporting steel hub, the wheels can be used dry, without coolant. Very little pressure need be applied to sharpen the tool, the weight of the tool alone being enough in many case. Unlike normal grinding wheels, there are virtually no sparks produced and the wheel and the tool remain significantly cooler than is the case with conventional wheels.