Mortageg Joinery Precision Calculator
Calculate structural dimensions and mechanical tolerances for woodworking joints.
Understanding Mortageg Mechanics
In structural woodworking, the "Mortageg" refers to the mechanical interface between two timber members. Unlike financial calculations, this physics-based approach focuses on the Rule of Thirds. This principle dictates that for maximum structural integrity, the thickness of the inner member should occupy exactly one-third of the total stock thickness.
The Physics of Joint Stability
When calculating dimensions for a joint, you must account for wood fiber compression and glue clearance. A joint that is too tight will starve the interface of adhesive, while a joint that is too loose lacks the mechanical friction necessary to resist shear forces. Our calculator uses the following logic:
- Tenon Thickness: Derived by dividing the primary stock thickness by 3.0.
- Tenon Width: Calculated by subtracting the dual shoulder offsets from the total stock width to prevent end-grain splitting.
- Mortise Depth: Always calculated as the tenon length plus a 2mm "expansion pocket" for excess adhesive and seasonal movement.
Real-World Example
Consider a standard table rail with a thickness of 21mm and a width of 75mm. If you require a 30mm tenon length with 5mm shoulders:
- The Tenon Thickness will be 7mm (21 / 3).
- The Tenon Width will be 65mm (75 – 10).
- The Mortise Depth must be at least 32mm to ensure the tenon doesn't "bottom out" before the shoulders meet the face of the wood.
Critical Safety Margins
Always ensure that the "haunch" or shoulder size is sufficient to hide the mortise slot. If the shoulder offset is too small (less than 3mm), the joint is susceptible to racking forces which can lead to catastrophic failure of the timber fibers under load.