Thanks for bringing that to our attention, I should have mentioned not to use just a single layer. I like rags for the top layer because grinding swarf does not bounce off, like it does on a smooth or hard surface. The rags provide a labyrinth to trap particles,and the oil is sticky, oil can not be used where sparks are generated, you don't want to start a fire. Unless the motor is totally enclosed, fan cooled, (TEFC), it must be protected, always including the shaft so nothing gets past the seals or into the bearings.