TechDraw Geometric dimensioning and tolerancing
Overview
The main purpose of a technical drawing is that others understand what the designer created with what tolerances and material and how to manufacture the design. To achieve this the system of Geometric Dimensioning and Tolerancing (GD&T) was developed for defining and communicating engineering tolerances.
TechDraws' capabilities to fulfill the common GD&T standards is still limited (as of FreeCAD 0.19) but you can achieve already many things. This Wiki page will explain what is implemented and what tricks are useful.
Dimensioning
TechDraw provides several tools to create different types of dimension. Please have a look at the different dimension on how to create and modify them.
Formatting
The default format for new dimension numbers depends on the preferences options Use Global Decimals and Alternate Decimals. This specifies the number of decimals, but in every case the dimension is a floating point number. For example if the setting is to have 2 decimals, the used format specifier is "%.2f" (floating point number with 2 decimals).
The number format can be changed:
- Select a dimension in the tree
- Go to the properties tab Data and there to the section Format
- The property DataFormatSpec contains the format specifier, so change it to what you need
The syntax of the format specifier is explained here.
Examples:
- You use 2 decimals but for an angle you want to have only one decimal use the format specifier %.1f.
- You use 2 decimals but don't like that zeroes are printed. So you prefer 4 instead of 4.00. Then use this format specifier: %g. The 'g' will use the shortest possible output and thus it omits trailing zeroes. Moreover it will automatically switch to scientific notation] if necessary..
Tolerancing
TechDraw allows you to add tolerances to every dimension.
Creation
- Create a dimension in your drawing
- Select the dimension
TechDraw
- Pages: Insert Default Page, Insert Page using Template, Redraw Page, Print All Pages
- Views: Insert View, Insert Active View, Insert Projection Group, Insert Section View, Insert Complex Section View, Insert Detail View, Insert Draft Workbench Object, Insert Arch Workbench Object, Insert Spreadsheet View, Insert Clip Group, Share View, Project Shape
- Stacking: Move view to top of stack, Move view to bottom of stack, Move view up one level, Move view down one level
- Decorations: Hatch Face using Image File, Apply Geometric Hatch to Face, Insert SVG Symbol, Insert Bitmap Image, Turn View Frames On/Off
- Dimensions: Insert Length Dimension, Insert Horizontal Dimension, Insert Vertical Dimension, Insert Radius Dimension, Insert Diameter Dimension, Insert Angle Dimension, Insert 3-Point Angle Dimension, Insert Horizontal Extent Dimension, Insert Vertical Extent Dimension, Link Dimension to 3D Geometry, Insert Balloon Annotation, Insert Axonometric Length Dimension, Insert Landmark Dimension, Adjust Geometric References of Dimension
- Annotations: Insert Annotation, Add Leaderline to View, Insert Rich Text Annotation, Add Cosmetic Vertex, Add Midpoint Vertices, Add Quadrant Vertices, Add Centerline to Faces, Add Centerline between 2 Lines, Add Centerline between 2 Points, Add Cosmetic Line Through 2 points, Add Cosmetic Circle, Change Appearance of Lines, Show/Hide Invisible Edges, Add Welding Information to Leader, Add Surface Finish Symbol, Add Hole or Shaft Tolerances
- Extensions:
- Attributes and modifications: Select Line Attributes, Cascade Spacing and Delta Distance, Change Line Attributes, Extend Line, Shorten Line, Lock/Unlock View, Position Section View, Position Horizontal Chain Dimensions, Position Vertical Chain Dimensions, Position Oblique Chain Dimensions, Cascade Horizontal Dimensions, Cascade Vertical Dimensions, Cascade Oblique Dimensions, Calculate the area of selected faces, Calculate the arc length of selected edges, Customize format label
- Centerlines and threading: Add Circle Centerlines, Add Bolt Circle Centerlines, Add Cosmetic Thread Hole Side View, Add Cosmetic Thread Hole Bottom View, Add Cosmetic Thread Bolt Side View, Add Cosmetic Thread Bolt Bottom View, Add Cosmetic Intersection Vertex(es), Add an offset vertex, Add Cosmetic Circle, Add Cosmetic Arc, Add Cosmetic Circle 3 Points, Add Cosmetic Parallel Line, Add Cosmetic Perpendicular Line
- Dimensions: Create Horizontal Chain Dimensions, Create Vertical Chain Dimensions, Create Oblique Chain Dimensions, Create Horizontal Coordinate Dimensions, Create Vertical Coordinate Dimensions, Create Oblique Coordinate Dimensions, Create Horizontal Chamfer Dimension, Create Vertical Chamfer Dimension, Create Arc Length Dimension, Insert '⌀' Prefix, Insert '〼' Prefix, Remove Prefix, Increase Decimal Places, Decrease Decimal Places
- Export: Export Page as SVG, Export Page as DXF
- Additional: Line Groups, Templates, Hatching, Geometric dimensioning and tolerancing, Preferences
User documentation
- Getting started
- Installation: Download, Windows, Linux, Mac, Additional components, Docker, AppImage, Ubuntu Snap
- Basics: About FreeCAD, Interface, Mouse navigation, Selection methods, Object name, Preferences, Workbenches, Document structure, Properties, Help FreeCAD, Donate
- Help: Tutorials, Video tutorials
- Workbenches: Std Base, Arch, Assembly, CAM, Draft, FEM, Inspection, Mesh, OpenSCAD, Part, PartDesign, Points, Reverse Engineering, Robot, Sketcher, Spreadsheet, Start, Surface, TechDraw, Test Framework, Web
- Hubs: User hub, Power users hub, Developer hub