Blend an edge

For when a rim blend takes too much, or when the edges you want are not one face's boundary.

The steps

1. Switch to Model.
2. Press Top to flatten the view. Silhouette edges then sit near the canvas border, which makes them much easier to hit.
3. Set the select mode to Edge 3 so you cannot catch a face by accident.
4. Click the edge. The blend dialog opens on it, naming the two faces that meet there.
5. Set a Size and a Reach.
6. Press Chamfer edge or Fillet edge.

Esc closes the dialog and drops the pick if you picked the wrong edge.

Reach

Three options, and this is the choice that matters.

Reach	Takes	Use for
Edge	This edge alone	When the neighbours must stay sharp
Chain	On through every tangent junction, stopping at the first corner	A boundary that runs smoothly through arcs
Loop	The whole loop this edge belongs to, corners and all	Rounding a hole

Chain is the default and is usually right. It follows the shape's natural continuity: where the geometry flows smoothly it keeps going, and where there is a genuine corner it stops.

Loop is the answer to "how do I round a hole", since a rim blend leaves holes sharp.

Size

For a chamfer, the setback along each face, giving 45 degrees. For a fillet, the radius. Greater than zero, and it accepts arithmetic.

A size that changes along the edge

Tick Taper along the edge and the size field splits into From and To, one for each end. A fillet then runs from one radius to another; a chamfer widens or runs out.

Ticking it sets the reach to Edge and keeps it there. A run of several edges has no single parameter to run the size along, so a taper only means anything on one edge.

Useful for a lead-in that starts wide and dies out, or a fillet that grows toward the loaded end of a bracket.

Both numbers must be greater than zero. To end at a sharp corner, use a small To rather than nothing.

Selecting the right edge

Edge picking is fiddly. What helps:

• Top view. The outline sits near the border and the edges are far apart.
• Edge select mode 3. Faces stop competing.
• Zoom in. The tolerance is a few pixels, so a bigger edge is an easier target.

Edges hidden behind the solid are not grabbable through it, so clicking near an outline picks the edge you can see.

It survives edits

A blend names its edge by the two faces meeting there, not by a number. Widen the plate and the chamfer is still on the corresponding edge of the wider shape.

When it refuses

That edge sits on a face the kernel could not name; blend another one. Usually a face produced by an earlier blend.

Also refused:

• A chain crossing between faces, so you cannot ask for one blend running around a boss rather than along a single face's boundary. Blend each face's boundary separately.
• A cylinder whose axis crosses the edge. No workaround.

Prefer a rim where you can

Two edge blends meeting at a corner do not mitre the way a single rim blend does, and with the fallback method they can leave a small spike. If both would give the shape you want, use the rim blend.

See also

• Blends, including the exactness note
• Rounding a body