T9 Widening joints: why alternate growth rings, and how to make one with a portable power tool (3 marks) · Industrial Technology Timber

T9 · Widening joints: why alternate growth rings, and how to make one with a portable power tool (3 marks)

Fits: 2015 Q12 (3), 2016 Q12 (3). Also 2019 MC7, 2024 MC2, 2018 MC10 · 140 words · 4 chunks

T9.1 · Why moveTimber moves as its moisture content changes, and back-sawn boards tend to cup away from the heart.T9.2 · AlternateWhen widening boards for a table top, alternate the growth rings (heart side up, then down). Each board then cups in the opposite direction to its neighbour, so the movement balances out and the top stays flat.T9.3 · BiscuitTo make the joint with a biscuit jointer: dress the edges straight and square, lay the boards out, and mark biscuit positions across each joint about 150–200 mm apart. Cut the slots in both edges with the biscuit jointer referenced from the face side.T9.4 · Glue + crampGlue the slots and edges, insert biscuits, and cramp with sash cramps, alternating cramps above and below to keep the top flat. Then check for flatness and clean off excess glue. Dowels, a Domino, or a router-cut tongue and groove also work.

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