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Surface feet per minute (SFPM or SFM) is an imperial and American customary unit of speed, being the number of linear feet that a location on a rotating component travels in one minute. Its most common use is in the measurement of cutting speed (surface speed) in machining. It is a unit of velocity that describes how fast the cutting edge of the cutting tool travels. It correlates directly to the machinability of the workpiece material and the hardness of the cutting tool material. It relates to spindle speed via variables such as cutter diameter (for rotating cutters) or workpiece diameter (for lathe work). SFM is a combination of ''diameter'' and the ''velocity'' (RPM) of the material measured in feet-per-minute as the spindle of a milling machine or lathe. The faster the spindle turns, and/or the larger the diameter, the higher the SFM. The goal is to tool a job to run the SFM as high as possible to increase hourly part production. However some materials will run better at specific SFMs. When the SFM is known for a specific material (''ex 303 annealed stainless steel = 120 SFM for high speed steel tooling''), a formula can be used to determine spindle speed for live tools or spindle speeds for turning materials. In a milling machine, the ''tool'' diameter is substituted for ''stock'' diameter in the following formulas when the cutter is revolving and the stock is stationary. Spindle Speed can be calculated using the following equation: :〔 ==See also== * Speeds and feeds 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「Surface feet per minute」の詳細全文を読む スポンサード リンク
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