【正文】 the cutting speed is normally measured in m/s. The feed motion f is provided to the tool or the workpiece and, when added to the primary motion, leads to a repeated or continuous chip removal and the creation of the desired machined surface. The motion may proceed by steps or continuously. The feed speed vf is defined as the instantaneous velocity of the feed motion relative to the workpiece (at a selected point on the cutting edge). For mining and drilling, the feed f is measured per revolution (mm/rev) of the workpiece or the tool。 engagement) is the distance that the cutting edge engages or projects below the original surface of the workpiece. The depth of cut determines the final dimensions of the workpiece. In taming, with an axial feed, the depth of cut is a direct measure of the decrease in radius of the workpiece and with radial feed the depth of cut is equal to the decrease in the length of workpiece. In drilling, the depth of cut is equal to the diameter of the drill. For milling, the depth of cut is defined as the working engagement ae and is the radial engagement of the cutter. The axial engagement (back engagement) of the cutter is called ap. The chip thickness hi in the undeformed state is the thickness of the chip measured perpendicular to the cutting edge and in a plane perpendicular to the direction of cutting. The chip thickness after cutting (i. e., the actual chip thickness h2) is larger than the undeformed chip thickness, which means that the cutting ratio or chip thickness ratio r =h1/h2 is always less than unity. Chip Width The chip width b in the tmdeformed state is the width of the chip measured alo ng the cutting edge in a plane perpendicular to the direction of cutting. For singlepoint too! operations, the area of cut A is the product of the undeformed chip thickness h l and the chip width b (., A = h1b). The area of cut can also be expressed by the feedf and the depth of cut a as follows: H1=f sink and b = a/sink Where k is the major cutting edge angle (i. e., the angle that the cutting edge forms with the working plane). Consequently, the area of cut is given by A =fa 。 that is, fzis the displacement of the workpiece between the cutting action of two successive teeth. The feed speed vf(mm/rain) of the table is therefore the product of the number of teeth z of the cutter, the revolutions per minute of the cutter n, and the feed per tooth(vf=nzfz). A plane containing the directions of the primary motion and the feed motion is defined as the working plane, since it contains the motions responsible for the cutting action. In turning the depth of cut a (sometimes also called back 11 0. 125mm is economical on both diameter and length of turn. Metalcutting processes are extensively used in the manufacturing industry. They are characterized by the fact that the size of the original workpieee is sufficiently large that the final geometry can be circumscribed by it, and that the unw anted material is remo ved as chips, particles, and so on. The chips are a necessary means to obtain the t in the economy of the parts machined on the automatic screw less than 1 000 parts may be more economical to set up on the turret lathe than on the automatic screw machine. The cost of the pans machined can be reduced if the minimum economical lot size is calculated and the proper machine is selected for these quantities. Since surface roughness depends greatly upon material tumed, tooling, and feeds and speeds employed,minimum tolerances that can be held on automatic tracer lathes are not necessarily the most economical tolerances. In some cases, tolerances of 177。s fingertips with produ