Overview
The DogBone tool modifies polyline geometry by applying specialized DogBone-style fillets to sharp interior corners. Unlike regular fillets, DogBone corners introduce small arcs that extend outward, allowing CNC tools with circular bits to accurately cut internal right angles.
The tool serves essential roles in CNC machining, laser cutting, routing, and woodworking, where precise fitting of components (especially interlocking joints, tabs, and mortises) is required.
Why DogBones?
In CNC operations, especially with round cutting bits, internal corners can’t be cut perfectly square due to the tool’s radius. This creates a problem when mating parts need to fit into 90° cutouts. DogBone fillets solve this by adding small arcs (resembling a dog bone shape) that remove additional material and ensure perfect part fitment.
Workflow Steps
- Launch the tool
Type the command DBONE_SP or click on Dogbone from SPCAD Ribbon
- Set Radius (Optional)
Type Radius to define the fillet radius for DogBone arcs (default applies if skipped).
- Select Mode
Type Polyline to apply DogBone to entire polyline corners, or press ENTER to manually select specific line segments.
- Tool Execution
The tool automatically adds DogBone arcs at qualifying corners and replaces sharp junctions with curved reliefs.
Technical Details
- The tool identifies corners by analyzing vertex angles.
- A DogBone arc is drawn outside the interior angle, centered tangentially to both adjacent segments.
- Works with closed or open polylines, and also supports individual Line segments.
- Radius defines how far the arcs protrude—a larger radius = more material removed.
- All arcs are constructed in the current UCS and 2D plane.
Use Cases
- CNC woodworking joints (tab slots, finger joints)
- Acrylic or sheet metal design requiring a mechanical fit
- Laser cutting templates for assembly models
- Manufacturing jigs or fixtures
Tips
Combine with JOIN if you want to merge DogBone arcs back into a polyline.