How to Use Ordinate Dimension in DraftSight?

Understanding Ordinate Dimensioning

Ordinate dimensioning is a method of dimensioning that provides a clear way to present the location of features on drawing layouts based on their distances from a specified reference point, known as the datum. This technique is particularly valuable in engineering and drafting as it emphasizes precise placement relative to a common origin, which simplifies the reading and interpretation of measurements.

Setting Up the UCS Origin

Before creating any ordinate dimensions, it is essential to establish the correct User Coordinate System (UCS) origin. To initiate the process:

1. Position your cursor over the desired datum point on your drawing (this could be a hole, edge, or other specific feature).
2. Use the command to move the UCS origin to that point. This will ensure that all subsequent dimensions are based on this reference, allowing for accurate measurements.

Creating Ordinate Dimensions

Once the UCS origin is set, you can begin adding ordinate dimensions:

1. Navigate to the Dimensions panel in the Annotate tab.
2. Activate the dimensioning command by selecting it or typing in the command shortcut for ordinate dimensions.
3. At the command prompt, type "o" to indicate that you wish to use the Ordinate command.
4. Decide if you want to avoid jogs in the leaders. If so, activate Ortho mode by pressing [F8]. This will keep your dimensions aligned appropriately.
5. Click on the feature that you wish to dimension. This point will serve as the location for the ordinate dimension.
6. Next, specify where you’d like the leader line to end by clicking at your desired endpoint. The dimension will now display the distance from the datum to the point you specified.

Modifying Existing Ordinate Dimensions

If changes are necessary for existing ordinate dimensions, follow these steps:

1. Select the ordinate dimension that you wish to edit.
2. Access the Leader tab, and from there, choose the option for Ordinate chain if you want to chain multiple dimensions together.
3. Make any additional adjustments as needed, such as modifying the leader or changing dimensional values.

Types of Dimensioning in Drafting

Be aware that there are multiple types of dimensioning techniques, including:

• Chain Dimensioning: Measures distances sequentially from one point to the next.
• Parallel Dimensioning: Places dimensions parallel to the feature being measured.
• Combined Dimensioning: Integrates different dimensioning methods for clarity.
• Progressive Dimensioning: Lists dimensions in a series to indicate incremental measurements.
• Dimensioning by Co-ordinates: Uses coordinate values for precise location.
• Equidistant Dimensioning: Measures equal distances across features.
• Repeated Dimensions: Displays the same dimension multiple times for emphasis.

Each method serves a unique purpose depending on the specific project requirements.

Understanding the Datum Origin

The datum origin acts as the central point from which all ordinate dimensions are measured. This reference point is established at the UCS origin. It’s crucial to remember that only one datum origin can be assigned to any part, which maintains consistency across the entire drawing.

FAQ

1. What is the difference between ordinate and baseline dimensioning?
Ordinate dimensioning measures distances directly from a datum to feature points, while baseline dimensioning relates multiple measurements to a single baseline reference for added clarity.

2. Can I edit an ordinate dimension once it has been created?
Yes, you can select an existing ordinate dimension and modify its properties or values using the dimension editing tools available in your software.

3. When should I use ordinate dimensioning over other methods?
Opt for ordinate dimensioning when precise location relative to a common origin is crucial, particularly in scenarios where many features depend on the same reference point for clarity and accuracy.