Machine element Drawing, Machine drawing.pptx

Machine Element Drawing

1. MACHINE DRAWING

2. Principle of Drawing To provide the correct information about drawings to all concerned people , the drawing must be prepared, following certain standard practices , as recommended by Bureau of Indian Standards (BIS). Sheet Size- For a reference size A0 having a surface area of 1 X = 841 mm and Y = 1189 mm.

3. Drawing Sheet Size Assembly Drawing Working Drawing

4. Title Block – Title of the drawing Sheet number Scale Symbol, denoting the method of projection Name of the firm / institute Initials of staff drawn, checked and approved.

5. Borders & Frames – Minimum 20 mm for size A0 & A1. Minimum 10 mm for size A2, A3, A4. Centering Marks Metric reference graduation Grid reference system Trimming mark

6. Types of lines and their applications

7. Types of lines and their applications

8. PROJECTION SYSTEMS

9. PROJECTION SYSTEMS 1. First angle system 2. Third angle system First Quadrant Third Quadrant - European country - ISO standard - Canada, USA, Japan, Thailand

10. ORTHOGRAPHIC PROJECTION 1 st angle system 3 rd angle system

11. ORTHOGRAPHIC VIEWS 1 st angle system 3 rd angle system Folding line Folding line Folding line Folding line  

12. ORTHOGRAPHIC VIEWS 1 st angle system 3 rd angle system Front View Front View Right Side View Right Side View Top View Top View

13. First angle system Third angle system PROJECTION SYMBOLS

14. S c ales The various types of scales used in machine drawing are Full scale 1:1 Reduced scale 1:X Enlarged scale X:1 The standard scales are given in Table

15. Dimensioning As far as possible, dimensions should be placed outside the view. Should be taken from visible outlines, not from hidden lines. Dimensioning to a centre line should be avoided except when the centre line passes through the centre of a hole. Each feature should be dimensioned only once in a drawing. Placed on the view or section that relates most clearly to the corresponding features. Each drawing should use the same unit for all dimensions, but without showing unit symbol. Minimum dimensions should be placed to define a whole part. No features of a part should be defined by more than one dimension in any one direction.

16. Elements of Dimensioning Dimension line — It is a thin continuous line terminated by arrowheads touching the outlines, extension lines or centre lines away from outline by 8 mm . Extension line (Projection line) — It is a thin line drawn outside and along the outline. There should be a gap of about 1 mm between the extension line and the outline. Leader line —One end of the leader terminates either in an arrowhead or a dot. The arrowhead touches the outline, while the dot is placed within the outline of the object. The other end of the leader is terminated at a horizontal line Arrowhead — An arrowhead is placed at each end of a dimension line. Its pointed end touches an outline, an extension line or a centre line. The length of arrowhead should be about three times its maximum width. The triangle of the arrow should be completely filled in.

17. Methods of indicating Dimensions Aligned system, and Unidirectional system. Aligned system — In the aligned system, the dimensions are placed above the dimension lines and may be read either from the bottom or from the right side of the drawing Unidirectional system — In the unidirectional system, all dimensions are placed with respect to the bottom of the drawing, irrespective of the disposition of the dimension line. In the system, the dimension lines are broken to insert their dimensions . This system is preferred for big drawings specially when it is not convenient to read the dimension from the right side or any other direction.

18. Symbols & Joints Welding Symbols

19. Limits , Fits and Tolerance The system in which a variation in dimensions is accepted is called the limit system. The allowable deviations are called tolerances. The relationships between the mating parts are called fits.

20. Tolerance : The permissible variation of a size is called tolerance. It is the difference between the maximum and minimum permissible limits of the given size . Limits: The two extreme permissible sizes between which the actual size is contained are called limits. The maximum size is called the upper limit and the minimum size is called the lower limit. Deviation : It is the algebraic difference between a size (actual, maximum, etc.) and the corresponding basic size. Actual Deviation: It is the algebraic difference between the actual size and the corresponding basic size. Upper Deviation: It is the algebraic difference between the maximum limit of the size and the corresponding basic size. Lower Deviation: It is the algebraic difference between the minimum limit of the size and the corresponding basic size .

21. S are then ap Tolerances HOLE BASIS SYSTEM, SHAFT BASIS SYSTEM In working out limit dimensions for the three classes of fits; two systems are in use, viz. , the hole basis system and shaft basis system HOLE BASIS SYSTEM: In this system, the size of the shaft is obtained by subtracting the allowance from the basic size of the hole. In this system, the lower deviation of the hole is zero. The letter symbol for this situation is ‘ H ’. SHAFT BASIS SYSTEM: In this system, the size of the hole is obtained by adding the allowance to the basic size of the Shaft. plied to each part. In this system, the upper deviation of the shaft is zero. The letter symbol for this situation is ‘ h ’.

22. Method of placing limit dimensions Method 1

23. Method 2

24. Method 3

25. Types of Fits 1. Clearance Fit – It is a fit that gives a clearance between the two mating parts.

26. Types of Fits 2. Transition Fit – This fit may result in either an interference or a clearance, depending upon the actual values of the tolerance of individual parts.

27. Types of Fits 3. Interference Fit - If the difference between the hole and shaft sizes is negative before assembly; an interference fit is obtained.

28. Schematic Representation of Fits

29. Surface finish The geometrical characteristics of a surface include, Macro-deviations, Surface waviness, and Micro-irregularities. The surface roughness is evaluated by the height, R t and mean roughness index R a of the micro-irregularities.

30. Surface Roughness Symbols

31. Machine Symbols: The basic symbol consists of two legs of unequal length, inclined at approximately 60° to the line, representing the surface considered. This symbol may be used where it is necessary to indicate that the surface is machined, without indicating the grade of roughness or the process to be used A. Basic symbol. B. Material Removal is Not Allowed C. Removal Of Material Is Allowed D. Special surface characteristics

32. Indication of Surface Roughness

33. Indication of Surface Roughness

34. Classification of Drawing Machine Drawing- Pertaining to machine parts or components. presented through a number of orthographic views. Size & shape of component is fully understood.

35. Production Drawing – Referred as working drawing. Should furnish all dimensions, limits & special finishing processes such as heat treatment, honing, lapping, surface finish, etc. Title should also mention the material used for the product, number of parts required.

36. Part Drawing- Detailed drawing of a component to facilitate its manufacture. Follows principles of orthographic projection Assembly Drawing- - A drawing that shows the various parts of a machine in their correct working locations.