Edge Joints

Edge joints are necessary when fitting narrow, solid timber boards together to make up a wider tabletop or panel. Shaped or profiled edges increase the gluing area, add strength and make it easier to align the boards when cramping together. The joint relies on the strength of the glue, although meeting edges must still be straight and square to the face side. Glue up as soon as possible after planing, before individual boards have a chance to distort.

Tools you need

  • Bench plane
  • Try square
  • Sash cramps
  • Try plane
  • 2H pencil
  • Glue
  • Steel rule
  • Straightedge

How To Make An Edge Joint

Plane the boards to approximate thickness before edge jointing. If they are to be cramped together, a slight hollow (convex) edge is acceptable. Additional pressure at both ends will reduce as the timber shrinks. Do not be tempted to glue together boards with rounded (convex) edges, however. Forcing the ends together by cramping will introduce stresses that could result in splitting ends.

1 Although harder to obtain, quartersawn timber is more stable than through-and-through cut wood. Select the boards and number their sequence with a pencil. Arrange growth rings alternately to minimize timber movement. Where possible, arrange boards so that their grain runs in the same direction. This will make it easier to plane the surface once you have glued the boards together, so reducing tear out. You should also take colour variation and figuring into account, especially if the panel is to be visible.

2 Insert the first board in the vice and check the edge with a steel straightedge and try square. Using the longest bench plane possible ­preferably a try plane – true up the edge. You will need to keep checking this until it is straight and square. Repeat the process on the other edge of the board. Planing two adjacent boards together gives a wider surface for the plane to run on. It is also less critical for the edges to be dead square if they are placed back to back in the vice (face sides outwards): the boards will still meet together neatly and create a flat face.

3 Before gluing up, do a dry run with the cramps. For long boards you will need several cramps, which you should position alternately above and below the timber. Use scrap wood behind the cramp shoes to prevent damage and to keep the cramps clear of the timber surface. Apply the glue and tighten the cramps. If the boards are raised unevenly, use an offcut and tap the joints flush with a hammer.

Variations

Loose-tongue Joint

To increase the gluing area and help boards stay flush, you can add a loose plywood tongue to the joint. Cut a groove along both edges using a router fitted with a slotting cutter. Adjust the groove for width so that the plywood is a push-fit and not too tight.

Tongue And Groove Joint

You can cut the tongue-and-groove joint in solid timber with a combination plane, although this tool has really been replaced by the router. First cut the groove in one edge so that you can adjust the width of the tongue to match in the meeting edge. When used in rustic furniture and joinery, tongue-and­groove joints are not usually glued, so the boards are free to move with changes in humidity.

Word Discription :

Face side A wide surface planed perfectly flat, selected to be exposed on finished work. Quartersawn Planks cut from a log radially, so that growth rings are greater than 45 degrees to the face. Exposes the best figure.

Rubbed glue joint Where two straight pieces of timber are joined together without cramping. Glue is applied, both edges rubbed together and left to cure.

Tearout Wood fibres tend to lift and break when planing timber in the wrong direction, or against the grain.

Through-and-through sawing When a log is sliced with a series of parallel cuts, leaving only the centre boards quartersawn.

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