School of Mechanical Engineering
MEC 355T M1R14
Term Paper Report
Theory of metal Cutting & Merchant circle
Submited by Submited to
Harpreet Gill Mr. Manjeet Khurab
Introduction To Metal Cutting:- Manufacturing processes can be broadly divided into four categories, viz., primary (casting, forging, moulding, etc), secondary (machining, finishing, etc.), tertiary(fabricating processes like welding, brazing, riveting, etc.), and fourth level processes (painting, electroplating, etc.). Secondary manufacturing processes are as important as any other level processes. These processes involve removal of material in the form of chips or otherwise, to give the desired shape, size, surface roughness, and tolerance on the workpiece obtained from the primary manufacturing processes. The machined components can be used as it is, or one can be assembled (sometimes using fabricating processes) and if required, given an aesthetic look by electroplating, painting, etc. Metarial Removal Processes :- Material removal processes can broadly be divided into two categories: traditional and advanced (non-traditional). Each of these categories can be further sub-divided into bulk removal processes (or cutting) and finishing processes. Traditional Cutting :- Traditional cutting processes can be classified as those which produce parts having surfaces of revolution and those which produce prismatic shapes. This classification is based on the type of motion imparted to the work and tool. Cutting tools used for material removal are classified in two categories : single point cutting tool and multi-point cutting tool (cutting tools having more than one cutting edge). The following section discusses how material removal takes place by using a single point cutting tool. Similar principles are applicable to the multiple point cutting tools as well.
The process of metal cutting is effected by providing relative motion between the workpiece and the hard edge of cutting tool. Such relative motion is produced by a combination of rotary and translating movements either of the workpiece or of the cutting tool or both. Depending on the nature of the relative motion, metal cutting process is called either turning or planning or boring, etc.
For different types of operations, one needs to have different types of machine tools. For example, lathe for turning, planer for planning, grinder for grinding, etc. Some of these machines (say, lathe, boring m/c, and drill) generate surfaces of revolution whereas others (planer, milling m/c, and shaper) make prismatic (or flat surfaces) parts. With the help of different types of tools, a lathe can perform various kinds of operations.
Conventionally, the translatory displacement of the cutting edge of the tool along the work surface during a given period of time is called ‘feed’( f ), while the relative rate of traverse of work surface past the cutting edge is designated as the ‘cutting velocity’ or simply ‘speed’ (Vc). In case of single point turning, Vc is the peripheral velocity of the rotating workpiece in meters per minute. In case of slab milling, it is the peripheral velocity of the milling cutter in meters/minute.
Operation| Motion of Job| Motion ofCutting Tool|
Turning on aLathe| Rotary motion of theWork| Axial movement of the tool| Boring on aLathe| Work rotation| Axial tool movement|
Drilling on adrill machine| Fixed| Rotations as well astranslatory feed| Planning| Translatory| Intermittent Translation|
Milling| Translatory| Rotation|
Grinding| Rotary/Translatory| Rotary|
Chip Formation :
Deformation in Metal Machining :- Figure shows a schematic diagram of material deformation during cutting and subsequently removal of the deformed material from the workpiece by a single point cutting tool. Because of the relative motion between...