This reinforced butt joint is more foolproof than using regular dowels, but it does require a portable biscuit jointer to cut a slot. A hardwood biscuit fits into a corresponding slot cut into both meeting edges and results in a fast, simple, yet strong, glued joint. You can use a router with a slotting cutter for straightforward edge-to-edge joints. Suitable for both solid timber and sheet materials, you can also use biscuits on mitred edges.
Tools you need
- Bench plane
- 2H pencil
- Steel rule
- Biscuit jointer
- Try square
- Damp cloth
There are three common size of hardwood biscuit available to suit different thicknesses of material :
No. 0 is for timber from 6 – 12 mm ( ¼ – ½ in) thick
No. 10 is for timber from 13-18 mm (½ – ¾ in) thick
No. 20 is for timber from 19 mm (¾ in) and above
All biscuits are the same thickness and fit a 4-mm (1/8 in) wide slot.
How To Make a Biscuit Joint
1 Plane the board edges to be jointed so they are straight and square. Check them against each other, then mark the positions of the biscuits, roughly 152 mm (6 in apart). It is sufficient to draw a pencil line across adjacent boards.
2 Select the correct size biscuit to suit the board thickness (see left). Adjust the cutter plunge depth on the biscuit jointer and set the fence so the slot will be centralized in the edge of the timber.
3 Rest the fence of the biscuit jointer on the board and align the guide at the front of the fence with the relevant pencil mark on the board’s face. Switch on the jointer and, keeping pressure downwards on the top handle, plunge the tool forwards into the board to make the cut. Make repeat cuts as necessary along the timber and into the edge of the corresponding board.
4 Brush PVA glue onto a biscuit, insert it into the first slot and tap home with a hammer. Work your way along the edges of both boards in the same way. Apply glue to the timber edges as well and push the boards together.
5 Cramp the boards together and check they are flat. Use cramps above and below to avoid the panel distorting. Wipe excess glue with a damp cloth.
Corner and T-joints
For end joints at 90 degrees, place the fence of the tool against the end of the mating board and make plunge cuts. Biscuits are glued as before.
For T-joints in the middle of a board, square a pencil line across to mark the position. Either hold the tool against the line by hand or, preferably, against a guide batten cramped to the surface. This will keep all the slots in line.
Word Discription :
Biscuit An oval-shaped dowel – made of compressed beech – inserted into matching slots in adjacent boards. Glue swells the fibres ensuring a tight-fitting joint.
PVA Polyvinyl acetate, a synthetic resin glue for wood. Excess can be cleaned up with water.