This article is written primarily to advise our newer and less experienced members of the importance of this often overlooked but vital piece of equipment. If your gouges or chisels aren’t sharp, you can not expect to cut your piece of wood effectively and likewise, if your grinding wheel isn’t “sharp” you can not expect to cut the steel of your tools effectively when sharpening them, it is as simple as that.
If you magnify the surface of a grinding wheel you see millions of minute carborundum particles with very sharp edges all stuck together and having equally minute gaps between each one. It is these sharp edges of carborundum that grind or cut the steel of your tools away and leave you with a cutting edge. The steel that is removed during sharpening is seen as red sparks and the majority of it shows as black dust underneath the wheel. The rest of it however gets stuck in the gaps between the carborundum particles and hides their sharp edges, and also, some of these sharp edges are blunted or worn smooth. The end result of this is patches of black or silver seen on the surface of the wheel, and a wheel that rubs the tool instead of cutting it so the tool gets hot and turns a lovely shade of blue. This is the time to re sharpen or dress your wheel and it is very simple providing that you have the means to do it.
Most turners use a long square stick of carborundum called a Devil Stone, they are easily obtained from tool suppliers and cost about 6.00. You simply switch on the grinder, rest the stone on the tool rest, touch it on one edge and move it across the front of the wheel. The surface of the wheel is removed taking with it the embedded metal and the blunt particles and leaves a new surface of clean, sharp edges that cut again. Don’t overdo it though, just enough to get rid of the black or silver patches because obviously, every time you sharpen or dress the wheel you make it slightly smaller and the more you do it the sooner you will have to buy a new one. The other important thing is to make sure that you move the devil stone in a straight line so that the front of the wheel ends up flat, and not concave or convex, most important when you come to sharpen a tool such as a skew that requires a straight edge. It is also very important to protect your eyes when dressing the wheel because the dust that comes off it will do serious damage to your eyes if it gets in there, so please remember to wear goggles.
A lot is written in adverts about grinding wheels, extolling the virtues of each one but remember, the writers of the adverts also sell the wheel so they would wouldn’t they. Claims are made that “our wheel keeps the tool cooler and cuts cleaner” but in my long experience, all wheels will cut almost as well as each other providing that they are dressed and the way to keep the tool cool is to grind slowly and gently. I have a grinder that was sold with a grey wheel on one end and a white wheel on the other and I use both wheels equally, some tools I grind on one and some on the other. I can honestly say that I find no difference in the sharpness of tools ground on one wheel or the other and the only time they turn mildly blue is when I press too hard or the wheel needs dressing. Others may have different views but those are mine, so why pay much more for a white or red or a ruby wheel than a common grey one when they will all cut well if treated well. Also, after 5 years of moderate usage, my wheels have only been reduced by dressing them from 6 to 5 1/2 inches diameter so don’t get sucked in by all of this hype and change them un-necessarily.
Fred Harris.
GRINDING WHEELS AND THEIR CARE