Anyone that has had experience grinding knows that not every grind job benefits from the use of coolant. From one side you would think that adding the cooling and lubricity of coolant will lead to less wheel breakdown, however, this is not always the case. Coolant in fact can lead to faster build up on your wheel, allowing the particles to fill the voids in your cutting surface faster. Once you loose the porosity in your grinding wheel, it causes the wheel to get pushed away from the material you are grinding rather than removing material. Of course many factors play a role in the speed at which that happens; from wheel grit and RPM to the length of cut and the composite of the wheel.