Is there a ʼFilletʼ tool for rounding 3D edges in Rhino?

Short Answer

Yes — Rhino 3D has a FilletEdge tool for rounding 3D edges on polysurfaces and solids. This is the most common professional method for adding edge radii to joined 3D geometry in Rhino. It works best on clean, well-joined solids. Small or complex fillets can still fail on tight geometry.

What You Need to Know Before

Warning: FilletEdge often fails on messy joins, tiny edge segments, or imported geometry with bad tolerances. A very common issue is trying to fillet after heavy trimming, which creates fragmented edges that Rhino cannot solve cleanly.

How-to

• Command: FilletEdge

• Shortcut: FilletEdge

• Quick Steps:

  1. Run FilletEdge from the Command line or Solid menu, then select the polysurface or solid you want to round.
  2. Click the edges to fillet, then set a Radius in the command options.
  3. Turn on Preview if available, confirm options like ChainEdges=Yes when needed, then press Enter to create the rounded edges.

Variables & Settings

• Key Setting: ChainEdges

  This option lets Rhino automatically continue the fillet across tangent-connected edges. It speeds up selection on clean solids, but on complex models it can grab more edges than intended, so review the preview carefully before accepting.

Why it Fails

• Cause 1 (Geometry): The radius is too large for the available face width, or the selected edges run into tight corners and tiny trimmed surfaces.
• Cause 2 (layers/Locks): The object is on a locked layer or part of a referenced workflow where the target geometry cannot be edited normally.
• Cause 3 (Command/Logic): FilletEdge is being used on unjoined surfaces or poor imported geometry when FilletSrf or rebuild/cleanup work is actually required first.

Quick Fix & Best Practice

• Quick Fix: Run ShowEdges to find naked or bad edges, then use Join or repair the geometry before trying FilletEdge again with a smaller radius.
• Manager’s Verdict: Use FilletEdge for production-ready solids with clean topology. Avoid leaving fillets until after excessive trimming or imported model edits, because edge quality drops and failure rates increase.

FAQ

Can Rhino fillet open surfaces too?
Yes, but for separate surfaces FilletSrf is often the better tool.

Why does FilletEdge preview work but fail on Enter?
Because the final surface intersection may collapse at corners or tight transitions.

Can I fillet several edges at once in Rhino?
Yes, use ChainEdges or manually select multiple edges in one FilletEdge operation.

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