When precision is non-negotiable, using machinery and tools that are correctly balanced contributes to a successful end product. This certainly rings true with any grinding operation. Correct handling and balancing of grinding wheels are crucial for both optimal performance and safe operation. Incorrect wheel mounting can lead to poor workpiece finish and bearing failure of the grinding machines. Before mounting any grinding wheel and to ensure that the best results are achieved, there are some factors that need to be considered, including a range of safety checks.
The specification of the grinding wheel must be relevant to the material that will be ground, and the speed on the machine must match the speed marking on the wheel. A thorough visual inspection and subsequent ring test will clearly indicate if the wheel is safe to mount for grinding. When a wheel is lightly tapped with a suitable wooden or plastic tool on the left and right side of the vertical centerline, a clear ping sound will be audible. If a dull sound is heard, the wheel is not suitable for mounting.
When mounting a grinding wheel, plus size bores are to be mounted with minus tolerance flanges to ensure a certain “play” of the grinding wheel’s bore and the flange shoulders. There are two ways a grinding wheel is mounted, either directly onto the machine spindle or onto a removable set of flanges, each having their own way to be mounted. Always ensure that care is taken with regards to the location of the arrow marked on the wheel, as it indicates the heaviest part of the wheel.
When mounting a wheel directly onto the machine spindle, the mounting arrow needs to point to the bottom (6 o’clock). Allow the wheel to settle onto the spindle before the retaining nuts are tightened. This enables the oversize bore to settle down on the shaft / flanges shoulder. The heaviest part of the wheel will be on the outermost point of the grinding wheels’ eccentricity and needs to be trued away to get the wheel into balance.
If you are mounting the grinding wheels onto a removable set of flanges, set the back flange horizontally onto a table or floor, then place the wheel bore onto the flange shoulder. Add the outer flange, insert a couple of bolts and nip lightly, allowing play between the wheel and flange. Raise the wheel vertically with the mounting arrow to the top (12 o’clock), allowing the flange shoulder to rest on the lighter side of the wheel. Insert the remaining nuts and tighten lightly. The heaviest part of the wheel will be on the outermost point of the grinding wheels’ eccentricity and needs to be trued away to get the wheel into balance.
Regardless of the procedure used, the retaining nuts must be torqued to the machine manufacturers values, and should be done diagonally / transversely to ensure even tightening.
The wheel is now ready to be mounted onto the grinder. Dress or true the high spots from the heavier part of the wheel first - a crucial step in contributing to a balanced mounted wheel. After this, the wheel’s lightest point needs to be marked. This is done by mounting the wheel on a static balancer. Remember to mark the lightest point with chalk.
Using flanges with two balancing weights, fit the weights symmetrically to either side of the top half of the balancing ring in relation to the chalk mark. Balance the wheel by moving the weights downwards at the same time and symmetrically in relation to the chalk mark until the wheel comes to rest. Rotate the wheel to ensure it remains at rest in whatever position you put it in. If it still rotates, continue to move the weights until you can lock the weights into position.
A Flange with three balancing weights has a slightly different procedure. Fit one balancing weight onto the center directly opposite the chalk mark (heaviest part of the wheel) and lock it into position. Fit the other weights symmetrically at either side of the center line of the flange, near to the top. Move these weights at the same time and symmetrically downwards until balance is achieved. Lock these two weights into position.
Finally, the wheel is now ready to be mounted onto the grinder. Ensure that the machine spindle is clean before the wheel is mounted. Remember to torque the flange bolts with a torque wrench.
A test run is always recommended after mounting a grinding wheel. During the start-up phase, idle speed is used, during which an optical and acoustic assessment is done. Before starting with the grinding process, the wheel needs to be dressed.
Following these recommendations can help avoid any serious injury or damage to the machine, and help improve on your overall grinding time and surface finish of the workpiece.
Grinding Techniques have locally been manufacturing specialised abrasives since 1981. With our local Research and Development Team, all products are continually tested and evaluated to ensure that optimum performance is achieved during application whilst adhering to all the international safety standards as set out by OSA and ISO.