The simplest and basic dressing process is to use a white aluminum oxide dressing stick. Maximum exposure is necessary to optimize the wheel performance. Because of the many grades of carbides, ceramics and other hard materials, the grinding process does not always allow the wheel to stay open and exposed. The same with CBN BORAZON® wheels. There are so many steel alloys over Rockwell C 54 and so many wheel bonds, particle sizes, and hardnesses, that it is sometimes necessary to dress a CBN wheel.
NOTE: One of the biggest misconceptions is that dressing reduces the life of the wheel. A loaded wheel grinds with greater grinding pressure and therefore gets a lower grinding ratio. A well dressed wheel grinds with lower grinding pressure and produces more parts in less time, and will last longer. This results in greater productivity and greater profits.
USE THE PROPER GRIT TYPE, AND GRIT SIZE DRESSING STICK For wheels with a mesh size of 270 and coarser, use a DIT Type A 220 Grit Stick. For wheels with a mesh size of 320 and finer, use a DIT Type AF 320 Grit Stick.
Generally, an aluminum oxide stick is used for dressing polyimide, resin, and some vitrified bonded wheels. Silicon carbide sticks are used on metal, some vitrious-metal, and vitrified bonded wheels. An SC 80 Grit Stick for wheels with a mesh size under 220, a SCF 320 Grit is for mesh sizes 320 and finer.
Black silicon carbide sticks are harder than aluminum oxide. Still some operators prefer aluminum oxide even on tougher bond systems. Since there are so many different grinding wheels and applications, i.e. wet, dry, and grit sizes, one has to determine which is the most effective stick. When dressing VITRIFIED BONDED SUPER ABRASIVE WHEELS, extreme care must be used. Dress very lightly and use a maximum 1" length of stick. Vitrified bonds have a built in porosity.
SOAK THE DRESSING STICK IN WATER Use only a stick which is thoroughly soaked. A soaked, wet abrasive stick does not grind away as easily as a dry powdery one. Because it is wet, you will have greater control of the removal of the wheel bond. Also, with a wet stick you will not get abrasive dust all over yourself and the machine.
DRESS AT NON-GRINDING SPEEDS Before pushing the stick into the wheel, turn off the power. As soon as the power is turned off, shove the stick STRAIGHT into the wheel until it skids to a stop. As the wheel slows down, it acts softer and therefore it will erode easier and is more controllable. Or, if possible, with a "grinding" speed control, reduce RPM to 1,000 SFPM (Surface Feet Per Minute). the power. As soon as the power is turned off, shove the stick STRAIGHT into the wheel until it skids to a stop. As the wheel slows down, it acts softer and therefore it will erode easier and is more controllable. Or, if possible, with a "grinding" speed control, reduce RPM to 1,000 SFPM (Surface Feet Per Minute).
DO NOT MOVE THE STICK SIDEWAYS In tooth type steel saw blades there are gullets, some larger... some smaller. A grinding wheel is similar. Larger mesh sizes have more clearance... smaller mesh sizes have less chip clearance. By moving the stick sideways, the bond on the side of the particle will be eroded. This will weaken the particle bond. Only plunge for optimum results.
TRUE AND DRESS/CONDITION YOUR CBN AND DIAMOND WHEELS With CBN BORAZON® the wheel must grind more concentrically to consistently make the correct size chips. Even if a wheel is dressed open at the factory, when they are mounted, they will need truing and dressing.
HOW GRINDING CAN BE ENHANCED
A "GRINDER" VARIABLE SPEED CONTROL changes the speed of the grinding wheel to a lower RPM. This makes the wheel act softer and opens up the chip clearance.
AN AIR JET ABRASIVE DRESSING SYSTEM automatically optimizes the exposure of the particle.
A WAX STICK, which has abrasive in it, dresses open a wheel while it is grinding a part.
A MOTORIZED DEVICE trues and dresses at the same time (German made Roll II).
A DIAMOND CUP WHEEL OR ROLL trues and dresses at the same time the parts are being ground (Continuous Dress).
A COMPUTER AIDED GRINDING SYSTEM MONITOR senses the energy level of the grinding process and changes the infeed rate and RPM automatically.
DRESSING COATED (PLATED) DIAMOND WHEELS A marginally effective way of cleaning out scale and swarf is to use an A 220 Grit Stick for 220 mesh and coarser wheels.
DRESSING COATED (PLATED) CBN BORAZON® WHEELS is NOT effective in dressing out a steel loaded wheel. Usually a loaded coated wheel cannot be opened up!
Get the answers to your
grinding questions. Call our
Certified Abrasive Engineers.
Harry G. Sachsel C.A.E.