 Hello friends, myself, Narendra Kartikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solapur. Now, I am going to discuss the topic, Surface Roughness Symbol. The learning outcome for this session at the end of this session, student will be able to understand the need of surface roughness symbol. Student will be able to apply the surface roughness symbol to the part drawing also. The content for this surface roughness symbol topic is likewise introduction, need of surface roughness symbol, surface roughness symbols in detail. Let us go with the first point, introduction, machine drawing and various symbols. As everybody knows that particularly engineering graphics rather the drawing is the language rather the mother tongue language for an engineers. Whatsoever the creations, designs, communications done by an engineers to the another engineer is through the means of majorly with the help of drawing itself. Whenever drawing is generated it includes the various geometries along with dimensions, conventions and various symbols. We know that particularly machine drawings is nothing but the subject delivering the various particular machine elemental drawings, detailed drawings, assembly drawings and many more. While drawing the particular such kind of part geometries it is required to be minimize the complications in the visualization of the drawing. The drawing includes the geometry, dimension and symbols means a full of particular such kind of elements into the big drawing. Now to represent the repeated geometry, to repeat the particularly standard geometries BIS conventions are there. Similarly, the very important parameter to the surface that is surface roughness symbol is also to be shown with a very specific and unified way. There should be a particularly a common kind of symbols to be used throughout the state nation rather globally. Let us go with the next point of discussion, need of surface roughness symbol. As just we had seen in general the various kind of drawings. Now let us particularly go with the type of drawings which we are going to learn or learn in the machine drawing. First production drawing, second assembly drawing and third many other drawings applications we are coming across like the drawings used for maintenance and many more. What is a part drawing? A part drawing is a drawing which is referred for manufacturing as well as for quality control checks also. Now to measure the particular dimensions along with the surface roughness you need to read whatever the values are shown in the form of symbols to the respective geometry. For the same we are going to use the surface roughness symbols for surfaces. In assembly drawing the matching surfaces are required to be shown with the particular surface roughness symbols so that after the assembly we will come to know what is the status of the surface contact and how the particular movement will be there after the assembly itself. Likewise many particular drawings purposes are solved with the means of surface roughness symbol which is shown on the drawing itself. After understanding the need of surface roughness symbol now let us go with the actual surface roughness symbols one by one. This particular symbol is nothing but a surface roughness symbol two legs are there this is called one leg another leg which is 60 degree at an angle from the ground rather than from the surface this hatched portion is nothing but a reference surface may be called as datum surface may be called as geometry surface of the part. Now this symbol is shown for the respective surface for which the surface roughness value is to be shown that means for outer peripheral side for example I need to show the surface roughness value I will mention the value at location A and this two leg drawing will be shown to the outer surface. The A is nothing but particularly surface roughness value and it is to be obtained by any production method the two legs are open this is not closed that means it represent that the surface roughness value to be achieved or achieved with the any production method. Now whenever there is a insisting that particularly surface roughness value to be achieved for this surface through only machining then the legs must be closed this legs must be closed and A once again mention that particularly surface roughness value many a times for quality checks the surface roughness value is to be measured for unmachined or wherever the material is not removed the such kind of surfaces surface roughness value is to be checked for the same the two legs will carry a one circle one circle it means the material removal is prohibited and rather particularly surface roughness must be obtained without removal of material. At this stage of the session are you able to recall share some of the example of mechanical elements where these symbols representation you had seen or used earlier in the drawing or sketches of any academic subject just enlist the same yes I think you had a recalled back that at the time of engineering graphics as well as the manufacturing processes subjects you had seen such kind of symbols and the resemblance of the same wherever it has been applied. Now these are the further more symbols we will see one by one this is the symbol A 1 to A 2 that means minimum surface roughness value to maximum surface roughness value which is allowed for this particular surface. The leg is further extended to the leader line and over which the milling the milled surface that means this surface roughness can be achieved through this particular machining method. This is the these are the two distinct kind of symbols. This symbol represent a see later over here where you can mention the sampling length for measurement of surface roughness many a time we require to check the surface roughness not for full surface but for small sample length. So this is mentioned at this location now to the right bottom side this perpendicular sign is mentioned what it exactly means that we will see in the next slide. This is one of the example how these symbols are shown this is the symbol which is used for outer surface and likewise. Let us go with the next important one surface roughness symbol which carries a full of information this is the triangle equilateral triangle extended line leader line. Now we will see the resemblance of alphabets and its position with respect to the information at location A position A roughness value in micrometers preceded by parameter symbol this is to be mentioned here. The B is nothing but just we are seeing in the last slide production method is to be mentioned like milling grinding etc. at the location C and oblique F or in bracket F many a time C stands for sample length sampling length in millimeters it is very important to remember that it is in millimeter. For this location surface roughness value other than RA micrometers so there is a surface roughness grade symbol what it means we will see that table in the next slide. So here E means machining allowance which is to be mentioned in the millimeter and the surface pattern is to be mentioned over here with the symbol. Surface roughness patterns are like this symbol parallel perpendicular cross multi-directional circular or radial according to the various kind of machining methods these are the different patterns and can be used these symbols at a particular location. As we had seen that other surface roughness value that is equivalent surface roughness grade symbol is to be mentioned that is from N12 to N1 so these later N1 to N12 has to be mentioned over there. So this is all about the particular surface roughness symbols the references are as follows machine drawing by Siddheeshwar Karnayya Shastri machine drawing by P. S. Gill S. K. Kataria and Sun's publications. Thank you.