Chamfer¶

In one sentence: Bevel selected edges of a Part shape with a flat angled cut, replacing the sharp edge with an angled face.

Overview¶

Workbench: Part · Menu: Part → Chamfer
Toolbar: Part Modeling · Shortcut: none

Chamfer creates a Part::Chamfer object that replaces selected sharp edges with flat angled faces. It is the "bevel" operation — the flat-cut equivalent of the rounded Fillet.

Intuition¶

Where a Fillet rounds an edge with a circular arc, a Chamfer cuts it with a flat diagonal face. Chamfers appear in:

Machining — an entry chamfer on a threaded bore guides a bolt into the thread.
Electronics — PCB corner chamfers prevent solder bridges.
Aesthetics — chamfered edges give a product a faceted, angular look.

The most common chamfer is equal-distance: both faces are cut back the same distance (producing a 45° chamfer). Unequal distances produce other angles.

When to use it¶

Entry chamfers on bores and counterbores.
Decorative edge bevels on mechanical or consumer products.
Replacing filleted edges where a flat face is specifically required.

When NOT to use it¶

Rounded edge — use Fillet.
Inside a Part Design Body — use Part Design Chamfer.

Step-by-step walkthrough¶

Select the shape in the model tree.
Part → Chamfer.
In the Chamfer dialog, the shape's edges are listed.
Select the edges to chamfer.
Set the Size (chamfer distance from the edge).
Click OK.

Parameters¶

Parameter	Type	Default	Description
Shape	Part object	—	The solid to chamfer
Edges	Edge list	—	Edges to chamfer (selected in dialog)
Size	Distance	1 mm	Distance of the chamfer cut from the edge (equal both sides)
Size2	Distance	—	Second distance for unequal chamfer

Python API¶

import FreeCAD as App

doc = App.newDocument()

box = doc.addObject("Part::Box", "Box")
box.Length = 30; box.Width = 20; box.Height = 15
doc.recompute()

# Parametric chamfer on all 12 edges
chamfer = doc.addObject("Part::Chamfer", "ChamferedBox")
chamfer.Base = box
# Tuple format: (edge_index, start_size, end_size)
chamfer.Edges = [(i, 1.5, 1.5) for i in range(1, 13)]
doc.recompute()

print(f"Chamfered volume: {chamfer.Shape.Volume:.2f} mm³")

Common mistakes and pitfalls¶

Same failure modes as Fillet

Co-planar seam edges from Boolean operations will cause chamfer failures. Run Refine Shape first.

Chamfer size must be smaller than adjacent face

If the chamfer size exceeds the width of an adjacent face, OCCT fails. Reduce the size.