13.1 Annotation – Add Dimensions to your Drawing

The purpose of dimensioning is to provide a clear and complete description of an object. A complete set of dimensions will permit only one interpretation need to construct the object. Dimensioning should follow these guidelines:
· Accuracy: Correct values must be given.
· Clearness: Dimensions must be placed in appropriate positions.
· Completeness: Nothing must be left out and nothing duplicated.
· Readability: The appropriate line quality must be used for legibility.
There are two types of dimension representation:
1) Dimension Line: The dimension line is a thin line, broken in the middle to allow the placement of the dimension value, with arrowheads at each end. An arrowhead length is approximately 3 times of line width. An extension line extends a line on the object to the dimension line.
2) Leader: A leader is a thin line used to connect a dimension with a particular area. A leader may also be used to indicate a note or comment about a specific area.

Hierarchical dimension placement

Dimension lines are placed hierarchically in 2 to 3 levels of overall dimension; wall dimension; and opening dimension. Overall dimensions are outermost dimension lines, and measure from outside edge to outside edge. Wall dimensions are the next dimension lines towards the plan, showing exterior wall or interior partition locations.
The closest dimension lines to the plan, opening dimensions, indicate window, door, and other opening locations. These three hierarchical dimension lines are placed 1/2" from each other. The innermost dimension, the opening dimension, are 1” to 1-1/2” away from the plan, never touching it.

Dimension technique

The text of the dimension is always written on the top or left of the dimension line. Extensions lines are used to bring the dimension line a distance from the object so it is easily read and not confused as part of the object. The extension line starts about 1/16” from the edge of the object, never toughing it. And it extends about 1/8” past the dimension line. At the intersection of the extension line and the dimension line is a “tick.” The tick mark on a dimension line is an important detail and crosses at a 45 degree angle at the intersection of the dimension and extension lines. It is typically 1/8” long, however this may vary with the size and scale of a drawing.
Use your best judgment, but typically a tick mark is the length of the overlap of the dimension and extension lines (for example if you overlap the lines by 1/8” then the tick mark will be 1/8” in length). The height of dimension text is typically between 3/16" to 1/8", but not below 3/32” when printed. This assures its readability. Dimension text doesn’t touch the line. See Figure 28 for an example.

Dimensioning angled objects

The location and angle of walls need to be shown with proper dimensioning techniques. To anchor the angled walls as a unique location, they should be measured along both an x and a y axis as in a grid. This way allows construction people to lay out angled walls easily. Perpendicular dimensions to the angled walls may be added to give better dimension information.

Dimensioning curved objects

The important point in dimensioning a curve is that the builder must be able to replicate the curve from a drawing to the site. To do this, three components should be included: actual curvature, location of center point of the curve, and extent of the curve. The actual curvature is denoted as radius of the curve, which emanates from the center point for the curve. The center point of the curve should
be also dimensioned by locating it along x and y axis to anchor the point. The extent of the curve which may be only part of a full circle or half circle should be measured by giving location information on the each end of the curve related to other objects on the drawing.

How to setup dimension style for your drawing

Command: DIMSTYLE
This command will open a Dimension Style Manager. Here you can creates New Styles, sets the current style, modifies style, sets overrides on the current style and compares styles.

Current Dimension Style
Displays the name of the dimension style that is current. The default dimension style is STANDARD. The current style is applied to dimensions you create.
Styles
Lists dimension styles in the drawing. The current style is highlighted. Right-click in the list to display a shortcut menu with options to set the current style, renames styles, and deletes styles. You cannot delete a style that is current or in use in the current drawing.
List
Controls the display of styles in the Styles list. Select All Styles if you want to see all dimension styles in a drawing. Select Styles in Use if you want to see only the dimension styles currently used by dimensions in the drawing.
Don’t List Styles in Xrefs
When selected, suppresses display of dimension styles in externally referenced drawings in the Styles list.
Preview
Shows a graphic representation of the style selected in the Styles list.
Description
Describes the style selected in the Styles list relative to the current style. If the description is longer than the space provided, you can click in the pane and use arrow keys to scroll down.
Set Current
Sets the style selected under Styles to current. The current style is applied to dimensions you create.
New
Displays the dialog box, in which you can define a new dimension style.
Modify
Displays the dialog box, in which you can modify dimension styles. Dialog box options are identical to those in the New Dimension Style dialog box.
Override
Displays the dialog box, in which you can set temporary overrides to dimension styles. Dialog box options are identical to those in the New Dimension Style dialog box. Overrides are displayed as unsaved changes under the dimension style in the Styles list.
Compare
Displays the dialog box, in which you can compare two dimension styles or list all the properties of one dimension style.
Following Dimension Style Dialog Box is displayed when you select New\Modify\Override Command Button. Here you can set properties for dimension styles. Following are the different collections of properties arranged in tabs:
1. Lines Tab: Sets the format and properties for dimension lines, extension lines, arrowheads, and center marks.

Dimension Lines
Color
Displays and sets the color for the dimension line. If you click Select Color (at the bottom of the Color list), the Select Color dialog box is displayed. You can also enter a color name or number.

Linetype
Sets the linetype of the dimension line.

Lineweight
Sets the lineweight of the dimension line.

Extend Beyond Ticks
Specifies a distance to extend the dimension line past the extension line when you use oblique, architectural, tick, integral, and no marks for arrowheads.

Baseline Spacing
Sets the spacing between the dimension lines of a baseline dimension. Enter a distance.

Suppress
Suppresses display of dimension lines. Dim Line 1 suppresses the first dimension line; Dim Line 2 suppresses the second dimension line.

Extension Lines
Controls the appearance of the extension lines.
Color
Sets the color for the extension line.
Linetype Ext 1
Sets the linetype of the first extension line.
Linetype Ext 2
Sets the linetype of the second extension line.
Lineweight
Sets the lineweight of the extension line.
Suppress
Suppresses the display of extension lines. Ext Line 1 suppresses the first extension line; Ext Line 2 suppresses the second extension line.

Extend Beyond Dim Lines
Specifies a distance to extend the extension lines above the dimension line.

Offset From Origin
Sets the distance to offset the extension lines from the points on the drawing that define the dimension.

Fixed Length Extension Lines
Enables fixed length extension lines.
Length
Sets the total length of the extension lines starting from the dimension line toward the dimension origin.

Preview
Displays sample dimension images that show the effects of changes you make to dimension style settings.
2. Symbols and Arrows: Sets the format and placement for arrowheads, center marks, arc length symbols, and jogged radius dimensions.

Arrowheads
First
Sets the arrowhead for the first dimension line. When you change the first arrowhead type, the second arrowhead automatically changes to match it. To specify a user-defined arrowhead block, select User Arrow. The Select Custom Arrow Block dialog box is displayed. Select the name of a user-defined arrowhead block but the block must be in the drawing.

Second
Sets the arrowhead for the second dimension line.
Leader
Sets the arrowhead for the leader line. To specify a user-defined arrowhead block, select User Arrow. The Select Custom Arrow Block dialog box is displayed. Select the name of a user-defined arrowhead block but the block must be in the drawing.
Arrow Size
Displays and sets the size of arrowheads.
Center Marks
Controls the appearance of center marks and centerlines for diameter and radial dimensions.
None
Creates no center mark or centerline.
Mark
Creates a center mark.
Line
Creates a centerline.
Size
Displays and sets the size of the center mark or centerline.
Dimension Break
Controls the gap width of dimension breaks.
Break Size
Displays and sets the size of the gap used for dimension breaks.
Arc Length Symbol
Controls the display of the arc symbol in an arc length dimension.
Preceding Dimension Text
Places arc length symbols before the dimension text.
Above Dimension Text
Places arc length symbols above the dimension text.
None
Suppresses the display of arc length symbols.
Radius Jog Dimensions
Controls the display of jogged (zigzag) radius dimensions.
Jogged radius dimensions are often created when the center point of a circle or arc is located off the page.

Jog Angle
Determines the angle of the transverse segment of the dimension line in a jogged radius dimension.
Linear Jog Dimensions
Controls the display of the jog for linear dimensions.
Jog lines are often added to linear dimensions when the actual measurement is not accurately represent by the dimension.

Jog Height Factor
Determines the height of the of the jog, which is determined by the distance between the two vertices of the angles that make up the jog.
Preview
Displays sample dimension images that show the effects of changes you make to dimension style settings.
3. Text: Sets the format, placement, and alignment of dimension text.

Text Appearance
Controls the dimension text format and size.
Text Style
Lists the available text styles. Click the button to displays the following dialog box where you can create or modify text styles.

Text Color
Sets the color for the dimension text.
Fill Color
Sets the color for the text background in dimensions.
Text Height
Sets the height of the current dimension text style. Enter a value in the text box. If a fixed text height is set in the Text Style (that is, the text style height is greater than 0), that height overrides the text height set here. If you want to use the height set on the Text tab, make sure the text height in the Text Style is set to 0.
Fraction Height Scale
Sets the scale of fractions relative to dimension text. This option is available only when Fractional is selected as the Unit Format on the Primary Units tab. The value entered here is multiplied by the text height to determine the height of dimension fractions relative to dimension text.
Draw Frame Around Text
When selected, draws a frame around dimension text.
Text Placement
Controls the placement of dimension text.
Vertical
Controls the vertical placement of dimension text in relation to the dimension line. (DIMTAD system variable)
Vertical position options include the following:
· Centered: Centers the dimension text between the two parts of the dimension line.
· Above: Places the dimension text above the dimension line. The distance from the dimension line to the baseline of the lowest line of text is the current text gap.
· Outside: Places the dimension text on the side of the dimension line farthest away from the first defining point.
· JIS: Places the dimension text to conform to a Japanese Industrial Standards (JIS) representation.
· Below: Places the dimension text under the dimension line. The distance from the dimension line to the baseline of the lowest line of text is the current text gap.

Horizontal
Controls the horizontal placement of dimension text along the dimension line, in relation to the extension lines.
Horizontal position options include the following:
· Centered: Centers the dimension text along the dimension line between the extension lines.
· At Ext Line 1: Left-justifies the text with the first extension line along the dimension line. The distance between the extension line and the text is twice the arrowhead size plus the text gap value.
· At Ext Line 2: Right-justifies the text with the second extension line along the dimension line. The distance between the extension line and the text is twice the arrowhead size plus the text gap value.

· Over Ext Line 1: Positions the text over or along the first extension line.
· Over Ext Line 2: Positions the text over or along the second extension line.

View Direction
Controls the dimension text viewing direction.
View Direction includes the following options:
· Left-to-Right: Places the text to enable reading from left to right.
· Right-to-Left: Places the text to enable reading from right to left.
Offset from Dim Line
Sets the current text gap, which is the distance around the dimension text when the dimension line is broken to accommodate the dimension text.
This value is also used as the minimum length required for dimension line segments.
Text is positioned inside the extension lines only if the resulting segments are at least as long as the text gap. Text above or below the dimension line is placed inside only if the arrowheads, dimension text, and a margin leave enough room for the text gap.

Text Alignment
Controls the orientation (horizontal or aligned) of dimension text whether it is inside or outside the extension lines.
Horizontal
Places text in a horizontal position.

Aligned with Dimension Line
Aligns text with the dimension line.
ISO Standard
Aligns text with the dimension line when text is inside the extension lines, but aligns it horizontally when text is outside the extension lines.

Preview
Displays sample dimension images that show the effects of changes you make to dimension style settings.