Basic Dimensioning Practices - Los Rios Community College District · 2013. 4. 2. · EDT 310 -...

EDT 310 - Chapter 18 - Basic Dimensioning Practices 1

Basic Dimensioning Practices

Sacramento City College

EDT 310


Dimensioning Practices

Dimensional information includes

Size dimensions.

Location dimensions.

Notes.



Size Dimensions

Size dimensions provide the size of physical

features.

A feature is any physical portion or

characteristic of a part or object such as:

Diameter of holes

Width

Length

Depth


Dimensioning Shapes


Dimensioning Flat Surfaces

Dimension flat surfaces by giving measurements for each feature.

Architectural drafting - show all dimensions.

Refer to Figures 18-17, 18-18


Architectural

Style


Mechanical Style


Dimensioning Cylindrical Shapes


The diameter and the length can be

dimensioned in one view.

Use the view where the cylinder appears

rectangular.


Dimensioning Square Features

Dimensioning Square/Rectangular shapes

Dimension in views where the length and

height are shown.


Dimensioning Square Features


Dimensioning Conical Shapes

Dimensioning Cones and Regular Polygons

Conical shapes - dimension two ways:

1. Give the diameters at both ends and the

length.

2. Give the taper angle and length.


Conical Shapes #1


Conical Shapes #2


Dimensioning Regular Polygons

Regular Polygon shapes –

Dimension by giving

the distance across the flats and

the length.


Location Dimensions


Location Dimensions

Location Dimensions

Location dimensions provide the location of

physical features on the object.

Location of holes from end

Datum Dimensioning

Chain Dimensioning

Location of windows/doors in buildings


Location Dimensions

Location dimensions are used to locate features on an object.

Holes

Offsets

Location dimensions do not provide size.


Location Dimensions

Holes and arcs are dimensioned in the view where they appear circular.

Rectangular features are dimensioned to their edges.


Location Dimensions

Two types of location dimensioning systems

Rectangular coordinates and

Polar coordinates


Location Dimensions

Rectangular coordinates are linear dimensions used to locate features from surfaces, centerlines or center planes

Use DIMLINEAR command.


Location Dimensions

Rectangular

Coordinate

Location

Dimensions


Location Dimensions

Polar

Coordinate

Location

Dimensions


Location Dimensions

In architectural drafting, windows and doors are dimensioned to their centers on the floor plan.


Location Dimensions


Location Dimensions

Polar coordinates

uses angular dimensions to locate features

from surfaces, centerlines or center planes.

Use DIMANGULAR command.


Notes


Notes

Notes

Notes give information about individual or

specific features on the drawing.

Two types

Specific Notes

General Notes


Notes

Specific notes

Relate to individual or specific features on the

drawing.

They are attached to the feature with a leader line.

General Notes

Apply to the entire drawing and

Are placed together in one area of the drawing.

Exact location depends on sheet size, and

industry, company or school practice.


Notes


Dimensioning Standards



Each drafting field uses a different type of dimensioning technique

Architectural.

Mechanical.

Civil.

Electronics.



Drafters should place dimensions in accordance with company and industry standards.

Use the company standard FIRST.

When no company standard exists, use industry standards.



Dimensioning standards are used so an object designed in one place can be manufactured or built somewhere else.



ASME Y-14.5M-1994 Dimensioning and Tolerancing Standard emphasized in the textbook.

M - means metric.

1994 is the year it was published.

ASME is the American Society of Mechanical

Engineers.


Dimensioning Formats



Unidirectional Dimensioning is

“Unidirectional” means one direction.

All dimension numbers and notes are placed

horizontally on the drawing sheet.

Numbers are read from left to right when

viewed from the bottom of the drawing sheet.



Aligned Dimensioning is

Used on architectural drawings.

Horizontal dimensions are read horizontally.

Vertical dimensions are read vertically from

the right edge of the sheet.


Dimension Styles used by Particular

Field of Work


Dimensions - Mechanical

Mechanical Field.

Uses Unidirectional dimensioning

Dimensioning parts.

Dimension Characteristics

1. Uses arrowheads for terminators.

2. Dimension line is broken

3. Dimension number is centered inside dimension

line.


Dimensions - Mechanical


Dimensions - Architectural

Architectural Field.

Uses Aligned dimensioning

Dimension Characteristics

1. Uses “tic” marks for terminators.

2. Dimension line is unbroken.

3. Dimension number is centered over dimension

line.

4. Dimension is aligned with surface.


Dimensions - Architectural



Dimensioning practices depend on

Product requirements.

What are you making?

Manufacturing accuracy.

Extreme precision vs approximate dimensions.

Standards.

What dimension standards exist for your industry?

Tradition.

How has your industry dimensioned in the past?



Compare dimensioning practices for:

Automobile. (decimal inches)

Architecture. (feet, inches, fractions of inch)

Microprocessor chip. (1/10,000 to 1/100,000

of an inch

Civil. (Miles or kilometers)

Each dimension type is appropriate for that discipline.



Precision is indicated by decimal places

Automobile. (decimal inches)

3 inches vs 3.0010 inches

Architecture.

40.343245 feet (???) !!

Civil.

40.365789 miles (???) !!

Precision must be appropriate for that discipline.



The number of decimal places shown on a dimension increases manufacturing costs!

Paper weight measurements

3.0000” x 4.0000” x 2.0000”

Vs

3” x 4” x 2”


Dimensioning Circles



Circles are normally dimensioned by giving the diameter.

Per ASME standard, arcs are dimensioned by giving the radius.

AutoCAD lets you dimension a circle or an arc by giving the diameter dimension.



Diameter dimensions are produced by:

Picking the Diameter Dimension button on the

Dimension Toolbar.

OR

Picking Diameter in the Dimension pull-down

menu.

OR

Typing DDI or DIMDIAMTER at the

Command: prompt.



When you use the DIMDIAMETER command, a leader line and diameter dimension value are attached to the cursor when you pick the circle or arc.

The leader can be dragged to any desired location and length before picking where you want it to be placed. The Mtext, Text and Angle options are

available.


Dimensioning Holes


Dimensioning Holes

Holes are dimensioned in the view where they appear as circles.

To dimension holes:

Give location dimensions to the center and a

leader showing the diameter.

Use the DIMDIAMETER command to

dimension the diameter.


Dimensioning Repetitive Features


Dimensioning Repetitive Features

Repetitive features are dimensioned by:

The number of repetitions

Followed by an X, a space, and the size

dimension.

The dimension is then connected to the feature with a leader.

Refer to Figure 18-37.


Dimensioning Arcs


Dimensioning Arcs

The standard for dimensioning arcs is the radius.


Dimensioning Arcs

Use the DIMRADIUS command to place a radius command by:

Picking the Radius Dimension button on the

Dimension toolbar.

OR

Picking Radius in the Dimension pull-down

menu.

OR

Typing DRA or DIMRADIUS at the Command:

prompt.


Dimensioning Fillets and Rounds


Dimensioning Fillets and Rounds

Small inside arcs are called fillets

Fillets are designed to strengthen inside

corners.

Small arcs on outside corners are called rounds.

Rounds are used to relieve sharp corners

Dimension each one individually as arcs or as a general note.

See Figure 18-39.


Dimensioning Angles


Dimensioning Angles

Coordinate and angular dimensioning are both acceptable for dimensioning angles.


Dimensioning Angles

Coordinate dimensioning uses coordinates to specify the length of line segments to start locations of angles.


Dimensioning Angles

Angular dimensioning

Locates one corner with a dimension and

provides the value of the angle in degrees.

You can dimension the angle between any

two non-parallel lines.


Dimensioning Curves

Where possible, curves are dimensioned as arcs.

Where curves are not of a constant-radius,

Dimension them to points along the curve

using the DIMLINEAR command.

See Figure 18-40.


Dimensioning Chamfers

A chamfer is an angled surface used to relieve sharp corners.

To dimension chamfers:

Show angle and a linear dimension

OR

Two linear dimensions

Basic Dimensioning Practices - Los Rios Community College District · 2013. 4. 2. · EDT 310 -...

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