How to Dress a Bench Grinding Wheel?
Before you start dressing a bench grinder wheel, make sure you check your grinding wheel dressing tool and grinding wheel for cracks by visual inspection and performing the ring test (we discussed this in the article about grinding wheels and grinding). After you are certain that the grinding wheel doesn’t have any cracks in it and isn’t dangerous, check the tool rest next. It should be as close to the grinding wheel as possible, just enough to have it run freely. Ideally would be leaving 1/16 of an inch between the tool rest and the wheel.
As the grinding wheel wears down, you’ll need to adjust the rest and move it closer. This is important, because if you leave a lot of space between the rest and the wheel, you are risking damaging your tools and more importantly, a serious injury. Namely, your dresser might get caught by the wheel and get pulled under it, causing your fingers or hand to raise and get hurt on the high-speed wheel. Also, spin the wheel with your hand just to see if it’s solid and not wobbly.
A lot of grinders have a spark-guard that has the purpose of keeping the sparks from wrapping around following the wheel spin and landing on your workpiece or your face. The spark-guard should also be adjusted really close to the wheel – 1/16 of an inch would also be ideal. In case your grinder doesn’t have a spark-guard, be even more careful. Some dressers, like the star dresser for example, will cause a lot of sparks to fly around, so safety glasses (a full facial protection along with the safety glasses is the ultimate protection!) are a necessary piece of protective gear.
Silicon carbide or aluminum oxide dust is the kind of dust you wouldn’t want to have in your lungs. Since even acute silicosis is a serious disease, make sure you invest in high-quality mask that you’ll use every time you dress. In case you like to keep your shop or a garage clean (and you probably do), cover your other machinery before you begin to avoid getting the abrasive dust all over other tolls and machines. Maintaining a clean work area is also important for cutting down on the likelihood of an injury.
Another very important note: do not wear long sleeves while dressing the grinding wheel as your shirt or a jacket can get caught in it. Same goes for long hair (if you have it, pull it back) and gloves – believe it or not, gloves can be an extremely dangerous piece of equipment when working on a bench grinder (unless you’re using a dresser with a longer handle) as they can get trapped between the wheel and the tool rest. Always take extra precautions like turning your grinder on while standing next to it and not in front of the wheel.
After you’ve taken all necessary precaution measures and got geared up, you’re ready to begin. The procedure is more or less completely the same for all discussed bench grinder dresser types: diamond dressers, dressing sticks and star dressers. Truing and dressing is performed by holding it against the rotating grinding wheel surface and moving it back and forth across the wheel face.
Turn on the grinder and allow the wheel to reach full RPM. Start by positioning the dresser off center to one end of the wheel. If you’re using a star dresser, you’ll place its legs behind the rest, apply the head of the dresser containing discs or cutters with force on the surface of the grinding wheel and you’ll run the tool back and forth. In case you are using a wide-face diamond dresser, you’ll apply its whole face with a light pressure against the whole surface of the wheel and move it back and forth just a bit. The dressing stick is also placed against the wheel face and moved back and forth. As for the single point diamond dressers, they are placed in a holder, point set at 10 to 15-degree angle pointing toward the direction of wheel rotation (make sure you turn the tool frequently 20-40 degrees to maintain a sharp point).
The whole process of dressing is not labor-intensive and will take about five minutes. Wheels should be trued & dressed just enough to establish concentricity or to expose new sharp abrasive grains to the workpiece. The process is over after you get a nice flat surface of the wheel that looks brand new.
IMPORTANT: Don’t forget to adjust the tool rest back to 1/16 of an inch away from the grinding wheel after you’re done dressing it.