Bracing Timber Sizes

[EssexMame]

To join the panels of the cabinet I understand I need bracing timber to join the sides to the back/front/bottom and so on. These are glued/screwed to each other.

I understand the bracing timber should be 1x2" (which is actually 3/4"x1 1/2" or 19mmx38mm). I've certainly found 19mmx38mm (in lengths to 2400mm generally here in the UK)

Should it be treated? kiln dried? What wood type - CLS, Spruce, something else? Should it be planed/sanded or will the rough surface (and cheaper) timber be ok or even what I should get - it can be sanded lightly or even left rough, I'd assume, as it is in the inside.

Also, do you screw through the longer side (38mm) or, as I expect, the 19mm depth? Into 3/4" (18mm) MDF that would be a screw length upto 37mm (or 56mm for the 38mm depth) ? I've already got 200 30mmx5mm countersink screws so the 19mm (then into 18mm MDF) should hold it all together pretty well without popping out the side from inside-to-out screwing... I'm glueing as well so that should hold it all in place pretty well - right?

[JDFan]

The screws are more just to hold things together while the glue dries so as long as they are long enough to secure the pieces together it will be fine (also not so long that they go through the outside of course )

As for the wood type the cheap stuff works just as well figure it isn't going to be seen in most cases so pretty much any scrap wood pieces you have or buy will work fine many people use furring strips since it is cheap.

Main thing I make sure to do is always predrill the holes before screwing to avoid problems like splitting\cracking (ie. bumps on the exterior of the cabinet due to the MDF swelling as the screw is forced in from the other side )



 

[kahlid74]

There are lots of ways to do this, but what you are referring to is commonly known as "furring strips".  They should be 3/4" x 3/4" x 4" or larger.  Anything thinner than 3/4" doesn't provide enough surface area for the glue to do it's thing.  Wood glue acts like welding, it chemically bonds to both sides creating a point stronger than the wood itself.  So surface area is important.

So for me, I typically take scrap 3/4" x 3/4" MDF from the actual sides/bottom/front and I cut them into 4-8" long strips and then use those.  I drill from the outside and use 1.75" long screws.  Counter-sunk from the outside they do have about 1/3" of the screw through the furring strip which is fine, since I go back with a Dremel and drop them all.  Some of the other guys use like 1.25" screws or 1.5" screws and go from the inside.

Whether you go from the inside or outside make sure your drill bit is large enough.  Some woods will be fine with a small bit and a large scew where others won't.  If your screw middle is bigger than your bit your MDF/plywood will swell and bulge nastily.

[EssexMame]

Great advice, thanks all. My MDF is 3/4" (18mm) and I have an extra sheet if I don't make any errors so think I'll use that. I want to drill from the inside so will stick with the 30mm (1.25" approx) screws I already have.

If I do end up having little/no scrap MDF though are the furring strips what I should get?

[Drnick]

Great advice, thanks all. My MDF is 3/4" (18mm) and I have an extra sheet if I don't make any errors so think I'll use that. I want to drill from the inside so will stick with the 30mm (1.25" approx) screws I already have.

If I do end up having little/no scrap MDF though are the furring strips what I should get?

Yes