Tongue & Groove#

A tongue cut from one board locking into a groove in another

Names: tongue_and_groove

When to use#

Use tongue_and_groove when one board's edge or end must lock flat into another's: floor and panelling boards, and above all the breadboard end of a solid tabletop, where a cap board runs across the end grain of the field boards. The tongue is the male board's own wood (an Add on its face, like a tenon); the groove is a blind cut in the female. Nothing is a loose spline. For a tongue that locks by its shape use sliding_dovetail; for a stub that goes into a pocket rather than a full-length groove use mortise_and_tenon.

Syntax#

joinery tongue_and_groove name=<Name> {
    tongue_thickness <mm>      // across the male's thickness, centred on the male mark (default 10, 3 to 40)
    depth            <mm>      // how far the tongue stands out of the shoulder (default 12, 3 to 40)
    clearance        <mm>      // optional; widens the groove only, never the tongue (ADR-0013)
    slot diameter=<mm> length=<mm> at=<mm>    // optional: elongated peg hole through the tongue
}
join joint=<Name> male=<Part>@<Mark> female=<Part>@<Mark>

• The male mark sits on the face the tongue stands out of, with its normal pointing out. The tongue spans the face's longer extent (the run) and is tongue_thickness across the shorter one (the flare), centred on the mark.
• The groove is tongue_thickness + clearance wide and depth + clearance / 2 deep, over the tongue's full run, so one groove per field board merges into the one continuous groove a breadboard end needs.
• slot is a stadium cut through the tongue's thickness, long axis along the run. length is the overall length (diameter plus twice the travel); at is the distance out of the shoulder (default depth / 2). Glued versus sliding is two joinery declarations, one with slot and one without, each named by the joins that want it.

Example#

project name="Breadboard end" units=mm schema_version=1 {
    materials { material Oak type=hardwood }

    component FieldBoard {
        stock Oak 100.0 50.0 20.0
        mark End x=50.0 y=50.0 z=-10.0 normal=pos_y
    }
    component Cap {
        stock Oak 100.0 50.0 20.0
        mark Groove x=50.0 y=0.0 z=-10.0 normal=neg_y
    }
    joinery tongue_and_groove name=Sliding {
        tongue_thickness 7.0
        depth 10.0
        clearance 0.1
        slot diameter=4.0 length=8.0 at=5.0
    }

    assembly Top {
        part Field instance=FieldBoard { pos x=0.0 y=0.0 z=0.0 }
        part Breadboard instance=Cap { pos x=0.0 y=50.0 z=0.0 }
        join joint=Sliding male=Field@End female=Breadboard@Groove
    }
}

examples/dining_table.kdl is the full case: eight field boards, BreadboardEndGlued for the centre boards and BreadboardEndSliding for the outer ones, with the cap's round peg holes cut as ordinary holes.

Pitfalls and diagnostics#

• The slot is a feature of the tongue, not a hole on the field board: a hole there would land in the visible tabletop, because the board as modelled has no tongue to carry it.
• The peg is not generated. slot and the cap's hole are the two holes it passes through.
• params (error): tongue_thickness or depth missing or out of range.
• material (error): the tongue is as thick as its board, or the groove does not fit across the female.
• facing, contact (error): the male's shoulder meets the female off square, or does not bear on its face.
• slot (error): not diameter=/length=/at=; length below diameter; the slot leaves the tongue along its depth or run.
• remaining-wall (warning): less than max(3 mm, 15 %) of the female is left beside the groove. tongue-overhang (warning): the tongue's run is longer than the face it goes into.
• One slot per joint; a very wide board that needs two is two joints at two marks.

See also#

• docs/adr/0022-tongue-and-groove.md and docs/rfc/0030-breadboard-elongated-mortises.md
• docs/KDL_AUTHORING.md section 8 (joinery kinds)
• docs/agent-reference/nodes.md (the node index)
• docs/styles/models/tongue-and-groove.kdl and breadboard-end.kdl (the glossary models)

Names#

Every name this page declares, how the example library uses it, and the shortest real use.

tongue_and_groove#

joinery kind; value in 4 of 116 examples (7 uses).

Shortest real use, from farmhouse_harvest_table.kdl:

joinery tongue_and_groove name=CapGlued {
    tongue_thickness 10.0
    depth           tongue_depth
}

Related terms#

• Groove
• Tongue and groove