9 Dimensioning in Drawings

 

Dimensioning

TOPICS

Introduction

Dimensioning components Dimensioning object’ s features Placement of dimensions.

Introduction

ENGINEERING DESIGN

PROCESS

Sketches of ideas

Design a part

Create drawings

Contractor or Manufacture

RESULT

Multiview Drawing

Dimensioning

TRANSFERRED INFORMATION

Shape,Size, Location

1. 1. Sizes and locations of features
      
   2. Material’s type
      Non-graphic information
      These informations are such as:

      DEFINITION

      Dimensioning is the process of specifying part’ s information by using of figures, symbols and notes.

      DIMENSIONING SYSTEM

2. Metric system : ISO and JIS standards
   

    

   Examples 32, 32.5, 32.55, 0.5 (not .5) etc.
   

   1. Decimal-inch system
      

      Examples 0.25″ (not .25″), 5.375″ etc.
      

   2. Fractional inchsyste Dimensioning Components

DIMENSIONING COMPONENTS

Extension lines Dimension lines

(with arrowheads)

Leader lines

Drawn with

4H pencil

Dimension figures Notes :

• local note
  
• general note
  

Lettered with

Note:All Construction lines should be with H or HB Pencil

2H pencil.

indicate the location on the object’s features that are dimensioned.

indicate the direction and extent of a dimension, and inscribe dimension figures.indicate details of the feature with a local note.

Recommended Practices

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.

COMMON MISTAKE

Visible gap

Do not break the lines as they cross object lines.

COMMON MISTAKE

Continuous

Dimension lines should not be spaced too close to each other and to the view.

COMMON MISTAKE

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. c

When there is not enough space for figure or arrows, put it outside either of the extension lines.

Angular dimension in degree with a symbol “o” place behind the figures (and if necessary minutes and seconds may be used together).

Length dimension in millimeters without

specifying a unit symbol “mm”.

The JIS and ISO standards adopt the unit of

The dimension figures are placed so that they are readable from the bottom and right side of the drawing.

1. Aligned method
   

    

   The dimension figures are placed so that they can be read from the bottom of the drawing
   

2. Unidirectional method
   

Place the notes near to the feature which they apply, and should be placed outside the view.

Always try to read horizontally.

10 Drill

LOCAL NOTES

COMMON MISTAKE

10 Drill

Too far

10 Drill

≈ 10mm

Dimensioning Practices

THE BASIC CONCEPT

Dimensioning is accomplished by adding size and location information necessary to manufacture the object.

Clear Complete

Facilitate the

• manufacturing method
  
• measurement method
  

This information have to be

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.

To dimension an angle use circular dimension line having the center at the vertex of the angle.

COMMON MISTAKE

ANGLE

Arcs are dimensioned by giving the radius, in the views in which their true shapes appear.

The letter “R” is always lettered before the figures to emphasize that this dimension is radius of an arc.

orfor

The dimension figure and the arrowhead should be inside the arc, where there is sufficient space.

Move figure outside

R 62.5

R 58.5

R 6.5

Size dimensions are diameter and depth. Location dimension must be located from its center lines and should be given in circular view.

Placement of Dimensions

1. Extension lines, leader lines should not cross dimension lines.

 

3. Extension lines of internal feature can cross visible lines without leaving a gap at the intersection point.

WRONG CORRECT

 

4. Do not use object line, center line, and dimension line as an extension lines.

 

5. Avoid dimensioning hidden lines.

6. Place dimensions outside the view, unless placing them inside improve the clarity.

 

6. Place dimensions outside the view, unless placing them inside improve the clarity.

JUST OK !!! BETTER

 

7. Apply the dimension to the view that clearly show the shape or features of an object.

8. Dimension lines should be lined up and grouped together as much as possible.

 

9. Do not repeat a dimension.