Rhino 3D Tip: Configure Document Units and Tolerances Before Modeling

Set your file’s units and precision before modeling—everything else gets cleaner, faster, and more reliable.

Start every project with the right template

• Use File > New and pick a template that matches your deliverable (e.g., Small Objects – Millimeters, Large Objects – Inches).
• Templates preconfigure units, tolerances, and annotation styles, saving time and reducing risk.
• Need more templates? Create your own and SaveAsTemplate for repeatable standards across teams. If you’re standardizing across offices, consider centralizing templates—licensing and deployment help available via NOVEDGE.

Set Units and Tolerances (type “Units”)

• Units: Choose the unit system your downstream tools expect (CNC/laser: often mm; AEC: inches/feet; rendering: any, but be consistent).
• Absolute tolerance: Aim for 10–100× smaller than your smallest modeled detail. Practical starting points:
  • Jewelry/3D printing (mm): 0.01 mm
  • Product design (mm): 0.02–0.05 mm
  • General inches workflow: 0.001–0.01 in
  Too tight = slow operations and heavy files; too loose = fails to Join/Boolean and leaks at export.
• Angle tolerance: 0.25° for surfacing, up to 1° for general work.
• Model vs display: Distance display precision only affects readouts; it does not change model accuracy.

Dimension styles and readouts

• In Document Properties > Annotation Styles, align units with your model and audience.
• Inches users: consider Architectural units with fractional precision (1/16" or 1/8") and appropriate rounding.
• For manufacturing drawings, keep decimal places consistent with tolerance expectations (e.g., 0.00 or 0.000 in; 0.01 or 0.001 mm).

Changing units mid-project (when you must)

• Run Units and choose whether to scale geometry. If moving inches → mm, Yes, scale usually preserves real-world size.
• After switching, re-evaluate absolute tolerance in the new unit. Example: 0.001 in ≈ 0.0254 mm—often too tight for large scenes.
• Check blocks and linked files for unit mismatches; audit with BlockManager. For team workflows and CAD exchange setups, see procurement and integration options at NOVEDGE.

Interoperability tips

• Match collaborators’ units to avoid cumulative rounding and scaling errors.
• Before exporting STEP/IGES/DXF/STL, confirm the target unit in the exporter to prevent silent rescaling.
• STL for printing: model in mm, keep absolute tolerance near 0.01–0.05 mm, and mesh/export at comparable settings.

Grasshopper considerations

• Grasshopper inherits document units. Set units first; otherwise, slider values and domain assumptions won’t match intent.
• After a unit change, revisit numeric inputs, panel notes, and bake targets to avoid scale surprises.

Quick checklist

• Pick the right template (units, scale, tolerance).
• Set Absolute tolerance relative to the smallest feature.
• Use sensible Angle tolerance (0.25°–1°).
• Align annotation styles with shop/clients.
• Lock standards into templates and share with your team.

Need licenses, training, or deployment guidance for a unit-consistent Rhino environment? Explore NOVEDGE for Rhino solutions and expert assistance.