How to dimension a drawing properly
Good dimensions let someone make or build from your drawing without measuring it. Bad ones leave gaps, contradict each other or clutter the drawing. A few simple rules fix most problems.
START DRAWING — FREEDimension what matters to the person using it
A builder needs overall sizes, wall positions and openings. A fabricator needs hole centres and edge distances. Ask what they will measure from, and dimension from that.
Run dimensions in chains or from one datum
Either chain them end to end along a wall, or measure everything from one edge (a datum). Do not do both for the same feature — a size given twice can disagree.
Keep them outside the shape
Place dimension lines just outside the object where possible, lined up in neat rows. Keep the smaller dimensions closest to the object and the overall size outermost.
Use the right type
In BenCAD's dimension tool: linear for lengths, radius (R) for arcs, diameter (Ø) for circles and holes, angular for angles, and arc length along curves. Mark hole centres with centre marks.
Add notes for what dimensions cannot say
Materials, finishes and "all dimensions in mm" go in notes or leaders, not squeezed onto dimension lines.
Questions
Should I dimension in millimetres or metres?
Millimetres are standard on UK construction and engineering drawings. Write "All dimensions in mm" in the title block.
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