Difference between revisions of "Sharpening Equipment"
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Latest revision as of 19:08, 9 May 2019
Any tool with a sharp edge needs to be sharpened periodically. Working with dull tools quickly becomes frustrating, and is actually more dangerous than working with sharp tools.
Bench grinders are the quickest and most economical way to get into power sharpening hand-held tools.
Although somewhat harder to find, "low-speed" bench grinders are considered to be a better choice. Low speed is a relative term as they turn in the neighborhood of 1750 RPM. Most bench grinders turn approximately 3600 RPM. The slower speed helps to keep from burning the cutting edge of the tool.
Unless purchased from a specialty seller, a bench grinder comes with stone wheels as standard. The standard wheels tend to be very economical and not particularly well suited to sharpening lathe and other hand-held tooling.
Replacement stone wheels are available in a number of grits and hardnesses. They also have an RPM rating. Finally, they are available in a number of materials.
The higher the number of the grit, the finer the ground surface will be. To some extent, this can affect the quality of cut on the workpiece, and can affect the amount of sanding required.
Hardness of the wheel is indicated by a letter. The further up the alphabet, the harder the wheel will be. The wheel needs to be soft enough to be friable, but hard enough to lave a relatively long life. Softer wheels sharpen with less heat buildup which helps to protect the temper of the metal in the tool. Softer wheels also continually shed particles of the grinding compound, which continues to refresh the grinding edge on the wheel.
The drawback to a softer wheel is that it needs to be trued more often. Truing the wheel means shaping the grinding surface of the wheel to be flat and parallel to the tool rest on the grinder.
In recent years, cubic boron nitride (CBN) wheels have become popular with woodturners. The wheels have a thin layer of CBN cutting abrasive around the outside of a steel or aluminum wheel. The advantage is that the size of the wheel never changes. In addition, the wheel never needs to be trued. The biggest disadvantage of a CBN wheel is the initial cost of the wheel. Some bench grinders have difficulty starting steel CBN wheels due to their greater mass.
Wet grinders turn relatively slowly in relationship to bench grinders. Wheel speed is well under 1000 RPM. Typically, there is one sharpening wheel on the machine and the other side has a honing wheel made of leather or some other materiel that can be charged with honing compound to polish the tool after it is ground. The wheel runs in a tank that is filled with water. The water serves to cool the tool as it is sharpened.
The most well known wet grinder is the Tormek brand. Jet makes makes one as well and there are other brands available, including Grizzly. Harbor freight features one in their catalog occasionally.
Tormek has a line of jigs that fits their sharpener.
Some experienced turners sharpen their tools freehand, but many of us need to use a jig of some sort that holds the tool at the correct angle to the wheel to be able to sharpen it evenly and repeatably across the bevel of the tool.
The jig can be purchased or made by the turner in his/her shop.
A common jig for a bench grinder is the Wolverine sharpening jig by Oneway tools. To sharpen gouges, the Vari-Grind accessory is a valuable addition to the tool.