RRB Junior Engineer / DMS / CMA 2019 · Question 3454 of 3719
Explanation: Milling is a process of producing flat and complex shapes with the use of a multi- point (or multi-tooth) cutting tool. The axis of rotation of the cutting tool is perpendicular to the direction of feed, either parallel or perpendicular to the machined surface. Milling is usually an interrupted cutting operation since the teeth of the milling cutter enter and exit the workpiece during each revolution. There are two basic types of milling operations: Down milling: It is also called as Climb milling. When the cutter rotation is in the same direction as the motion of the workpiece being fed. The cutting force is maximum at the beginning and minimum at the end of the cut. In down milling, the cutting force is directed on to the work table, which allows thinner parts to be machined without susceptibility to breakage. A better surface finish is obtained. Up milling: It is also called as Conventional milling. In which the workpiece is moving towards the cutter, opposing the cutter direction of rotation. The cutting force is minimum during the beginning of the cut and maximum at the end of the cut. In up milling, the cutting action tends to lift the workpiece and hence, A proper fixture is required in this operation.
Source: RRB JE 2019 (CBT 2) (ME) Previous Year Paper (31 Aug 2019) — prepp.in solved-paper PDF (answer key with explanations) · reliable-secondary
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