Wood assembly - biscuit joint
Wood assembly - biscuit joint
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Difficulty:
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In woodworking, wood assembly without nails or screws yields a more natural, attractive and professional finish. The joining method is chosen according to one’s tools, knowledge, and habits as well as according to the project at hand.
Quick and easy to make, with the right tools, the biscuit joint is particularly useful when making furniture, drawers and cupboard doors as well as when joining several boards meant to be used as a tabletop. The technique uses a compressed wooden strip (called a “biscuit”) rather than a dowel to join two pieces of wood. Once glued in the slits where it is inserted, the biscuit (humidified by the glue) expands thus making a very sturdy joint.
Before Assembly
The biscuit joiner is designed to produce, with few measurements, a slit of the correct thickness and width. With an adjustable platform, the joiner can also be used for producing an angle slit.
There are four biscuit sizes, each identified with a number. In increasing order of length, those numbers: No. 9 (not commonly used), No. 0, No. 10 and No. 20. The thickness of the first biscuit (No. 9) is 1/8" and requires an adapted blade; the other biscuits are 5/32" thick, which corresponds to the standard blade. The most commonly used biscuit is No. 20.
Rule:
Always use the biggest biscuit possible given the thickness of the piece of wood.
- • No. 9 - piece of wood less than 5/16" thick;
- • No. 0 - for parts of 5/16" to ½";
- • No. 10 - for those of 5/16" to ½";
- • No. 20 -for pieces of wood thicker than 5/8".
Two or more biscuits are usually used side by side when the pieces of wood are particularly thick.
Note:
An adapter is used for changing an angle grinder into a biscuit joiner, because the overall shape of the two tools is very similar.
It is also possible to use a router, with the appropriate bit, but the technique is different from the one described below. It also requires a little more time and experience with the tool.
Glue
Wood or construction glue will strengthen any type of joint. In the case of biscuits, however, glue not only establishes a link based on adherence, but also humidifies the biscuits, which then expand in the slit, thus producing a physical link between the two parts to be joined.
Steps
The example shown below illustrates how to laterally join a piece of wood A to another piece of wood B.
1.1 Mark a reference point on A, at a precise distance (e.g.: 3" from the end).
2.1 Align the biscuit joiner with this point.
2.2 Make the first slit (follow the manufacturer’s instructions to know the correct use and adjustment of your tool).
3.1 Inscribe a reference point on B at the same distance as on A (e.g.: 3" from the end).
3.2 Make the second slit.
4.1 Insert the biscuits in the slits.
4.2 Assemble the boards without using glue.
4.3 If the joint is satisfactory, take it apart.
5.1 Apply glue on both sides of the biscuit.
5.2 Insert in the first slit, then in the second one.
5.3 Tighten with clamps.
5.4 Dry excess glue.
The key techniqueThis technique, which is similar to that of biscuits, applies to mitre cut joints (e.g.: frames).
1. Cut kerfs in the joint’s outer corner.
2. Insert wood tabs.
3. Allow the glue to dry.
4. Use a back saw or a file to remove tab tips that protrude, while take care not to damage the surface.
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