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A trick my machinist instructor showed me for getting the tool on center was to place a steel ruler against the stock and bring the tip of the tool up against it to hold it. If the ruler is leaning out toward you above the bit, the tool is too low, if leaning away, too high. When the tip of the tool holds the ruler perfectly straight up and down, the tip is on center.
Formula for RPM:
(Cutting Speed of material X 4) divided by diameter of the workpiece. Rule of thumb: Mild steel, 100 surface feet per minute cutting speed with HSS Cast iron, half of that. Aluminum, of course,can be turned much faster. Usually, carbide tools can turn twice as fast as HSS. HSS is far more practical for making special tools for cutting O ring grooves and such. Grind HSS with aluminum oxide wheels. Grind carbides with silicon carbide. These break down quickly by design to keep the cutting surface of the wheel as sharp as possible to cut the hard carbide. If you try to grind carbides with an aluminum oxide wheel, you will just glaze the wheel and create a lot of heat. Knurling: Use a feed of at least .025" - .040" A deep cut and light feed is the best way to remove stock quickly. A parts washer pump, a five gallon drum and some coolant hose is a simple and quick way to provide cutting lubricant to the tool. Emulsifiable cutting oil is not terribly expensive. It will improve surface finish immensly and prolong tool life. A good book to learn with is Technology of Machine Tools by Krar, Oswald and St. Amand, ISBN 0-07-035425-1, published by McGraw Hill.
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