The behaviour of chip on rake face of the tool caught the attention of many investigators because it was found that the value of coefficient of friction at tool chip interface is very high. It has been established that the normal stress on the interface due to the cutting force reaches such a high value that yielding occurs and the [...]
The following points highlight the top five theories on mechanics of metal cutting in the industries. The theories are: 1. Ernst-Merchant Theory 2. Merchant Theory 3. Stabler Theory 4. Lee and Shaffer Theory. 1. Ernst-Merchant Theory: According to this theory: This is based on the assumptions: (i) That expenditure is minimum in the process, i.e., shear will take plane in [...]
The following points highlight the four main types of chips formed during metal cutting. The types are: 1. Discontinuous Chip 2. Continuous Chip 3. Continuous Chip with Built Up Edge 4. Inhomogeneous Strain-Chip. Type # 1. Discontinuous Chip: These chips are small segments which adhere loosely to each other and form slightly larger length. Discontinuous chips are formed when the [...]
In this article we will discuss about the meaning and geometry of chip formation from metals in the industries. Meaning of Chip-Formation: In any machining operation, the material is removed from the workpiece in the form of chips, the nature of which differs from operation to operation. As the form and dimensions of a chip from any process can reveal [...]
The following points highlight the six main factors affecting metal cutting in the Industries. The factors are: 1. Velocity 2. Size of Cut 3. Tool Geometry 4. Tool Material 5. Ductile Materials 6. Forces Involved in Metal Cutting. Factor # 1. Velocity: It directly affects the temperature at tool point. If velocity is so low that the temperature at tool [...]
For metal cutting to be effective, it is necessary that tool takes the form of a large angled wedge. This tool must be driven asymmetrically into the work material, to remove a thin layer from a thicker body. The layer removed must be thin so that imposed stress on tool and work is within limits. Further a clearance angle must [...]
In orthogonal cutting, the tool approaches the workpiece with its cutting edge parallel to the uncut surface and at right angles to the direction of cutting. Thus tool approach angle and cutting edge inclination are zero. The study of forces acting on a tool during the process of metal cutting is necessary for making the analysis of the process on [...]
Some of the devices that have been used to measure such small deflections by dynamometer are described below: Device # 1. Dial-Indicator: This is the simplest form of deflection measuring device and can measure accurately upto 25 x 10-4 mm when functioning properly. These should be rigidly mounted on some suitable stand. However, dial- indicators are subjected to striking and [...]
The following are the characteristics of strain rings: i. Strain-rings provide high ratio of sensitivity to stiffness at the same time having adequate stability against buckling. ii. A ring can be easily produced and is simple to mount. iii. The fact that the inside is always in an opposite state of strain from the outside, allows four active arms to [...]
Tool geometry concerns with the basic tool angles, i.e. angles ground on tool to make it efficient in cutting. A single point tool has only one cutting edge and is most widely used in industries. It is designed with sharp edges to minimize rubbing contact between tool and work-piece. Factors like cutting tool life, surface finish on work-piece, force required [...]