Plywood joinery mistakes - DIY woodworking India

Plywood joinery mistakes - DIY woodworking India

Perpendicular join

Welcome. We DIY woodworkers often work on plywoods, the most available solid woods in and around. We often have to join them in different ways to build different kinds of structure. For example, while working on a simple kitchen cabinet, we join them using nails, screws etc. But are we joining them in the correct way? I hope so. Let's see the figure below.

Consider it as a wall mount cabinet, the left side and the bottom. Look at the joinery. We usually screw them from side penetrating the bottom. Is it the correct way? It is not. Why? The plywood can really hold it strong when you penetrate it perpendicular to the surface. But it is not when you penetrate it along the surface. Multiple thin wooden surfaces are fixed or attached together using adhesives applying high pressure and that is how, a plywood is made. When the nail or the screw goes along the join, instead of making the join strong, it will put pressure to make it apart.

Consider that the nail goes inside the base as shown in the picture. When we put weight on the base, the area around the nail gets weaker. The more weight we put, the more weaker the base surface becomes.

The correct ways will be use of L bracket or use of beading or use of groove.

This way the screws are always go perpendicular to the plywood surface without making it weaker in the internal joins. Another way can be keep the vertical part of L inside the side part. That way you can hide the bracket. In both the cases you may have to extract some wood from the plywood surface so that the bracket sits at the same level of the surface.

In the beading way, the extra piece of beading plywood provides a solid strength. The base plywood sits on top of it. The nails go perpendicular here as well.

There is another way. You have to make a groove line in the side cabinet and the base goes into it. Let me illustrate it.

The groove is made using a wood router. For instance, in a 18mm plywood, the groove is around 4-6 mm deep and 18mm wide(may be slightly more considering if we use laminate to the whole base). In that groove, the edge of the base goes in perfectly and the sides hold the base quite strongly. I like this way very much because it looks clean and feels strong due to the locking. Over and above, you use screws from side to keep it still, just still as it is already strongly held.


To be continued.