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A machine taper is a system for securing cutting tools or toolholders in the spindle of a machine tool or power tool. A male member of conical form (that is, with a taper) fits into the female socket, which has a matching taper of equal angle. Almost all machine tool spindles, and many power tool spindles, have a taper as their primary method of attachment for tools. Even on many drill presses, handheld drills, and lathes, which have chucks (such as a drill chuck or collet chuck), the chuck is attached by a taper. On drills, drill presses, and milling machines, the male member is the tool shank or toolholder shank, and the female socket is integral with the spindle. On lathes, the male may belong to the tool or to the spindle; spindle noses may have male tapers, female tapers, or both. == Explanation == Machine tool operators must be able to install or remove tool bits quickly and easily. A lathe, for example, has a rotating spindle in its headstock, to which one may want to mount a spur drive or work in a collet. Another example is a drill press, to which an operator may want to mount a bit directly, or using a drill chuck. Virtually all milling machines, from the oldest manual machines up to the most modern CNC machines, utilize tooling that is piloted on a tapered surface. The machine taper is a simple, low-cost, highly repeatable, and versatile tool mounting system. It provides indexability, as tools can be quickly changed but are precisely located both concentrically and axially by the taper. It also allows high power transmission across the interface, which is needed for milling. Machine tapers can be grouped into self-holding and self-releasing classes. With self-holding tapers, the male and female wedge together and bind to each other to the extent that the forces of drilling can be resisted without a drawbar, and the tool will stay in the spindle when idle. It is driven out with a wedge when a tool change is needed. Morse and Jacobs tapers are an example of the self-holding variety. With self-releasing tapers, the male will not stick in the female without a drawbar holding it there. However, with good drawbar force, it is very solidly immobile. NMTB/CAT and HSK are examples of the self-releasing variety. For light loads (such as encountered by a lathe tailstock or a drill press), tools with self-holding tapers are simply slipped onto or into the spindle; the pressure of the spindle against the workpiece drives the tapered shank tightly into the tapered hole. The friction across the entire surface area of the interface provides a large amount of torque transmission, so that splines or keys are not required. For use with heavy loads (such as encountered by a milling machine spindle), there is usually a key to prevent rotation and/or a threaded section, which is engaged by a drawbar that engages either the threads or the head of a pull stud that is screwed into them. The drawbar is then tightened, drawing the shank firmly into the spindle. The draw-bar is important on milling machines as the transverse force component would otherwise cause the tool to wobble out of the taper. All machine tapers are sensitive to chips, nicks (dents), and dirt. They will not locate accurately, and the self-holding variety will not hold reliably, if such problems interfere with the seating of the male into the female with firm contact over the whole conical surface. Machinists are trained on keeping tapers clean and handling them in ways that prevent them from being nicked by other tools. CNC tool-changing cycles usually include a compressed-air blast while one toolholder is being swapped with the next. The air blast tends to blow away chips that might otherwise end up interfering between the toolholder and spindle. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Machine taper」の詳細全文を読む スポンサード リンク
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