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The proper use of blotters can aid in preventing wheel breakages. Blotters, by definition, are compressible washers that must be placed between an abrasive wheel and a mounting flange. These blotters are more than just cardboard or paper, but are designed to strict standards for material type, thickness, coefficient of friction, and compressibility. Use only blotters that are supplied or recommended by the abrasive wheel manufacturer.

Blotters help to assure that the flange clamping pressure is evenly distributed on the wheel. They tend to cushion the pressure of flanges against any high points or uneven surfaces. They also prevent damage to the surfaces of the flanges from the coarser abrasive surfaces of the wheel. You must therefore use one clean new blotter for each mounting flange.

Additionally, blotters provide a better coefficient of friction than would be obtained between the flanges and the wheel without blotters, thereby providing better transmission of the driving power to the wheel.

“What diameter blotter must I use when mounting a grinding wheel?” The answer is simple. The blotter must be equal to or greater than the machine’s mounting flanges. In other words, wheel blotters should NEVER be smaller than the machine’s mounting flanges. The grinding wheel is driven by the machine flanges. The forces that drive the wheel are transmitted through the bearing surface of the flanges. The surface that drives the wheel (bearing surface) must always be in contact with the side of the wheel. A flange that is larger than the wheel’s blotter will hang over the blotter and not make full contact with the side of the grinding wheel. This lack of contact (overhang) could lead to wheel slippage, uneven or increased side pressure and breakage.

The lesson is simple, use only blotters that are equal to, or larger than the machine mounting flanges. Never re-use old blotters when remounting wheels. Never use a blotter smaller than the machine’s flanges.

For additional information on this topic or any other grinding wheel safety information, please review ANSI, OSHA and literature provided by the grinding wheel and machine manufacturer. Contact IRS with any additional questions.

We’ve added the EZ Choice MRO Product Line including Bonded Abrasive Products, Diamond and cBN Wheels, Diamond Tools, Coated Abrasives, and Non-Woven Products.

Credit: Roger Cloutier, Senior Product Safety Engineer at Saint-Gobain Abrasives, Inc.