Architectural millwork & joinery tolerances.
Fit is a measured decision.
A joinery drawing should explain how parts meet after conditioning, finishing and assembly. Nominal dimensions alone leave the workshop to invent the most important part: the fit.
Specimen schedule
Nominal dimensions are reference examples. Inches, when selected, are rounded to three decimal places.
| Feature | Reference geometry | Nominal size | Fit review |
|---|---|---|---|
| Tenon thickness | Centred on rail | 8 mm | Trial against actual cutter |
| Tenon length | Engagement into stile | 28 mm | Leave glue relief |
| Rail thickness | Finished stock | 24 mm | Measure after surfacing |
| Shoulder width | Bearing each side | 8 mm | Check squareness |
| Mortise depth | Blind cavity | 30 mm | Avoid hydraulic lock |
| Edge radius | Tool-dependent corner | 4 mm | Match internal radius |
Mortise and tenon as a system
Size the joint from the member geometry, load path and machining method. The illustrative section is not a structural approval. A trial joint in the intended material reveals compression, tear-out and assembly force better than an isolated numerical tolerance.
Tolerance belongs to a process
State a datum face and identify critical dimensions. Tool runout, cutter wear and moisture changes can all alter the final fit. Apply the tolerance to the finished condition, and record whether a coating is included in the allowance.
CAD profiles and cutter geometry
Internal corners follow the cutter radius unless a secondary operation changes them. In a CAD profile, distinguish the desired finished boundary from the tool-centre path. Keep compensation in one place so the radius is not applied twice.
Dry assembly before adhesive
Check shoulder contact, alignment and clamp access before adding adhesive. Provide space for excess glue in blind joints and follow the adhesive supplier’s instructions for open time and pressure. A forced dry fit may swell further during bonding.