You can only work to the limit of whatever milling machine or lathe you purchase will allow. NO ONE, nut even a very skilled tool maker, can compensate for a low quality machine. Typical things to look for are, hardened & ground "V" type ways, steel gears in the headstock, accurate vernier dials on the carriage, compound & tail stock, a cam lock type spindle nose, hard steel chuck, a spindle that can except 5-C collets, etc., etc.
Jim Allen