Dimensioning unit 2
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This document provides guidelines for dimensioning engineering drawings in 3 sentences: Dimensioning involves specifying an object's size, location, material, and other information using extension lines, dimension lines, leader lines, and notes to facilitate manufacturing and measurement. Key guidelines include placing dimensions outside views for clarity, using aligned or unidirectional methods for dimension figures, and noting radii, holes, chamfers, and rounded ends according to manufacturing needs. The document demonstrates best practices and common mistakes to avoid for clear and complete dimensioning of drawings.
Dimensioning unit 2
- 1. UNIT 2 Dimensioning Subject : Basics of Engineering Graphics - Diploma Sem 2
- 2. Contents Introduction Dimensioning components Dimensioning object’ s features Placement of dimensions.
- 3. DEFINITION Dimensioning is the process of specifying part’ s information by using of figures, symbols and notes. This information are such as: 1. Sizes and locations of features 2. Material’s type 3. Number required 4. Kind of surface finish 5. Manufacturing process 6. Size and geometric tolerances
- 4. DIMENSIONING COMPONENTS Extension lines Dimension lines (with arrowheads) Leader lines Dimension figures Notes : - local note - general note Drawn with 4H pencil Lettered with 2H pencil.
- 5. indicate the location on the object’s features that are dimensioned. EXTENSION LINES
- 6. EXTENSION LINES Leave a visible gap (≈ 1 mm) from a view and start drawing an extension line. Extend the lines beyond the (last) dimension line 1-2 mm. Visible gap COMMON MISTAKE
- 7. Do not break the lines as they cross object lines. COMMON MISTAKE Continuous EXTENSION LINES
- 8. Dimension lines should not be spaced too close to each other and to the view. 11 34 Leave a space at least 2 times of a letter height. 16 35 DIMENSION LINES Leave a space at least 1 time of a letter height.
- 9. DIMENSION FIGURES The height of figures is suggested to be 2.5~3 mm. Place the numbers at about 1 mm above dimension line and between extension lines. COMMON MISTAKE 11 11 34 34
- 10. 16.25 16.25 or DIMENSION FIGURES When there is not enough space for figure or arrows, put it outside either of the extension lines. 1 Not enough space for figures Not enough space for arrows 1 1
- 11. The JIS and ISO standards adopt the unit of Angular dimension in degree with a symbol “o” place behind the figures (and if necessary minutes and seconds may be used together). DIMENSION FIGURES : UNITS Length dimension in millimeters without specifying a unit symbol “mm”.
- 12. 1. Aligned method 2. Unidirectional method The dimension figures are placed so that they are readable from the bottom and right side of the drawing. The dimension figures are placed so that they can be read from the bottom of the drawing. Do not use both system on the same drawing or on the same series of drawing (JIS Z8317) DIMENSIONING METHOD
- 13. 30 30 30 30 EXAMPLE : Dimension of length using aligned method.
- 14. 30 30 30 30 3030 30 30 EXAMPLE : Dimension of length using unidirectional method.
- 15. 45o 45o 45o 45o EXAMPLE : Dimension of angle using aligned method.
- 16. 45o 45o 45o 45o 45o 45o 45o 45o EXAMPLE : Dimension of angle using unidirectional method.
- 17. LOCAL NOTES Place the notes near to the feature which they apply, and should be placed outside the view. Always read horizontally. 10 Drill COMMON MISTAKES 10 Drill ≈ 10mm 10Drill Too far
- 18. THE BASIC CONCEPT Dimensioning is accomplished by adding size and location information necessary to manufacture the object and component. Clear Complete Facilitate the - manufacturing method - measurement method This information have to be
- 19. L L S S S Designed part EXAMPLE To manufacture this part we need to know… 1. Width, depth and thickness of the part. 2. Diameter and depth of the hole. 3. Location of the holes. “S” denotes size dimension. “L” denotes location dimension. S L L
- 20. ANGLE To dimension an angle use circular dimension line having the center at the vertex of the angle. COMMON MISTAKE
- 21. FILLETS AND ROUNDS Give the radius of a typical fillet only by using a local note. R6.5 If all fillets and rounds are uniform in size, dimension may be omitted, but it is necessary to add the note “ All fillets and round are Rxx. ” NOTE: All fillets and round are R6.5 Drawing sheet R12 unless otherwise specified. NOTE: All fillets and round are R6.5
- 22. f xx Use leader line and local note to specify diameter and hole’s depth in the circular view. HOLES : SMALL SIZE xx Drill, Thru. 1) Through thickness hole f xx Thru. or xx Drill. or or
- 23. f xx, yy Deep HOLES : SMALL SIZE or xx Drill, yy Deep Hole’s depth Use leader line and local note to specify diameter and hole’s depth in the circular view. 2) Blind hole
- 24. f xx Use extension and dimension lines Use diametral dimension line Use leader line and note HOLES : LARGE SIZE
- 25. COMMON MISTAKE f xx f xx f xx Rxx f xx HOLES f xx
- 26. CHAMFER Use leader line and note to indicate linear distance and angle of the chamfer. S S q For a 45o chamfer S SCS or
- 27. ROUNDED-END SHAPES R12 f 12 21 5 Dimensioned according to the manufacturing method used. Center to Center Distance
- 28. ROUNDED-END SHAPES R12 21 5 12 Dimensioned according to the manufacturing method used. Center to Center Distance
- 29. ROUNDED-END SHAPES Dimensioned according to the manufacturing method used. R12 21 12 16
- 30. ROUNDED-END SHAPES R12 27 12 Dimensioned according to the manufacturing method used. Tool cutting distance
- 31. ROUNDED-END SHAPES Dimensioned according to the standard sizes of another part to be assembled or manufacturing method used. 25 Key (standard part)
- 32. ROUNDED-END SHAPES Dimensioned according to the standard sizes of another part to be assembled or manufacturing method used. 20
- 33. 1. Extension lines, leader lines should not cross dimension lines. POOR GOOD RECOMMENDED PRACTICE
- 34. 2. Extension lines should be drawn from the nearest points to be dimensioned. POOR GOOD RECOMMENDED PRACTICE
- 35. 3. Extension lines of internal feature can cross visible lines without leaving a gap at the intersection point. WRONG CORRECT RECOMMENDED PRACTICE
- 36. 4. Do not use object line, center line, and dimension line as an extension lines. POOR GOOD RECOMMENDED PRACTICE
- 37. POOR GOOD 5. Avoid dimensioning hidden lines. RECOMMENDED PRACTICE
- 38. POOR GOOD 6. Place dimensions outside the view, unless placing them inside improve the clarity. RECOMMENDED PRACTICE
- 39. JUST OK !!! BETTER RECOMMENDED PRACTICE 6. Place dimensions outside the view, unless placing them inside improve the clarity.
- 40. 7. Apply the dimension to the view that clearly show the shape or features of an object. POOR GOOD RECOMMENDED PRACTICE
- 41. 8. Dimension lines should be lined up and grouped together as much as possible. POOR GOOD RECOMMENDED PRACTICE
- 42. 9. Do not repeat a dimension. POOR GOOD RECOMMENDED PRACTICE
- 43. References • http://www.engineering108.com/pages/Engineering _graphics/Engineering_graphics_tutorials_free_dow nload.html • A text book of engineering graphics- Prof. P.J SHAH • Engineering Drawing-N.D.Bhatt • Engineering Drawing-P.S.Gill