I got an email from a fellow asking about what type of mounted stones I used for working with aluminum. I figured it would be good to share the information here also. Here's a copy of the answer that I sent him.
Hi Darrell,
These mounted stones are all on .125 shanks. They come in 3 grades that I know of, coarse, medium and fine. They are categorized by their colors, brown, blue and white. Generally I use the blue grade. They also are made with varying shapes, cylindrical, conical, disc type etc., and they also come if a multitude of sizes. For instance you can get the conical ones starting at about .125 at the tip and .187 where they are bonded to the shank. They go up form there in many different steps. I have a single point diamond dressing stone that I use for my bench grinder and if I need a certain shape I just spin it and reshape it with the dressing stone.
Most of the tool suppliers, Enco, Travers etc carry them. Most of the time I buy mine from a local tool and die supply business.
For cutting aluminum I have a stick of cutting lubricant. It's a green waxy substance that keeps the aluminum from sticking to the stone. The piece I have I've had for years. You just spin the stone and rub it on the stick. Once the grains are coated you can grind quite a bit of material.
I hope this answers your question.
George