Cutting & joints

Equal half-lap depth

d = \frac{t}{2}

t_{r} = \frac{t}{2}

Explain this equation

Gives the recess depth for a flush half-lap joint between two members of equal thickness.

t is the member thickness in millimetres. d is the depth of material removed from each piece. tr is the thickness left in the lapped part.

For the faces to finish flush, each member gives up half its thickness. Two halves overlap to make up one full thickness.

A 44 mm member is cut 22 mm deep, leaving 22 mm. Thicker stock simply scales the cut in proportion.

Watch out: this is the nominal depth only. It does not check whether a lapped joint is strong enough for a structural member.

Calculate the nominal recess depth for equal-thickness members.

Enter your values to see the result.

Equal-thickness flush half lap only. Does not verify joint strength, fasteners or suitability for structural members.

This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.