What it is
JoinerSim is an instant web‑based tool that calculates the precise clearance needed between two pieces of wood for a chosen joint—such as dovetail, mortise & tenon, or rabbet—while factoring in the inherent tolerance of the joint and any additional shrinkage that common hardwoods can exhibit during drying or acclimation. The result is expressed in millimetres and allows crafters to trim their cuts with confidence that the joint will fit snugly without excess play or forced interference and ensuring a durable bond.
How to use it
Enter the measured thickness in millimetres for both boards, select a joint type from the drop‑down list, provide the wood species shrinkage percentage, then submit. The tool multiplies the average board thickness by the sum of the base clearance and supplied shrinkage, dividing by 100 to produce the required clearance in millimetres.
Worked example
Example based on standard dovetail joint with shrinkage: avg thickness 46.5 mm, base clearance 1.5 % + shrinkage 5 % = 6.5 %, clearance 46.5 × 6.5/100 = 3.0225 mm.
Inputs
- Thickness of Piece 1 (mm): 45
- Thickness of Piece 2 (mm): 48
- Joint Type: 1
- Wood Shrinkage (%): 5
Result
- Required Joint Clearance (mm): 3.0225
Frequently asked questions
Why is average board thickness used instead of the minimum or maximum?
Using both boards’ dimensions yields a realistic clearance that accounts for cuts on each face, mitigating extreme variations for a balanced fit.
Can I input laminate or composite panels?
Treat all plies as part of the overall thickness and enter their summed millimetres. The calculation applies regardless of lamination orientation.