CNC and 3D-printing notes
Every joint guide has a “Can you CNC this?” section on what makes that joint easy or hard on a 3-axis machine. These are the general rules that apply to all of them.
Inside corners are always rounded
A round cutter cannot leave a sharp inside corner, so every recess and mortise keeps the tool radius. Either round the mating edges to match, or add dogbone reliefs in the corners so a square tenon can go fully home. Where a through tenon’s end shows, a rounded tenon usually looks neater than a visible dogbone.
Sloping faces, undercuts and curves
Shapes that widen away from the cutter, such as dovetails and tapered pins, cannot be reached by a straight bit from above; they may need a dovetail bit, a tilted setup or several setups. Coped shoulders on round legs and stretchers are curved surfaces and may need a fourth (rotary) axis or ball-nose 3D finishing, usually followed by hand fitting.
Holding long parts
Tenons are often on the end of a long part, which may have to be clamped upright or cut from the sides in several setups.
The STL files
There is one file per part, exported in its assembled position. Each is a closed (watertight) solid with its mortises and slots already cut by the mating parts, ready to import into CAM or modelling software. The proportions are illustrative, not measured from a particular object, and the files are unitless: scale them to suit and test the fit and allowances on offcuts before cutting good wood. Wood moves with humidity, so leave room for it.
Licence
The STL files are released under CC BY 4.0; please credit “Chinese Joinery”.