ᐅ Attaching the BILLY bookshelf back panel – which screws are best?

Hello everyone,

I am planning to fully assemble my Billy bookshelf and am currently wondering about the best way to attach the back panel. Since the back panel usually consists of thin particleboard or hardboard, I am curious which screws are ideal for this so that the back panel is securely held without causing too much damage to the material.

Are simple small wood screws sufficient, or would it be better to use specialized screws? It is also important that the back panel does not warp or split, as I might need to remove it later.

Perhaps you have experience with the BILLY bookshelf or know the suitable types and numbers of screws, as well as tips on the appropriate screw length and thickness?

Thank you in advance for your helpful advice!

alberttau schrieb:
Since the back panel is usually made of thin chipboard or hardboard, I wonder which screws are ideal to securely hold the back panel without damaging too much material.

Good question! 🙂 In my experience, thin wood screws with fine threads and a diameter of about 3.5 mm (about 0.14 inches) work great. I would recommend a length of 25-30 mm (about 1 to 1.2 inches) so the screw holds well in the cabinet without going all the way through.

It’s best to pre-drill to avoid splitting. Don’t tighten the back panel too much, or it might cause warping. Usually, tightening it loosely is enough.

Good luck with the screwing, it will turn out fine! 😉

For the back panel of BILLY, I always use 3.5 x 25 wood screws with fine threads. Important: pre-drill the holes, otherwise the back panel tends to split easily.

Cecilera66 schrieb:
For the back panel of BILLY, I always use 3.5 x 25 wood screws with fine threads.

Interesting, but do you understand why fine threads are better? Many people use coarse threads for wood, but with the thin back panel, that can cause the material to break down.

In theory, you could also use thinner sheet metal screws and attach it with pre-drilled holes. However, this might reduce the grip in the grain. Therefore, it depends on the material of the back panel: HDF boards are more brittle than particle boards.

theo63 schrieb:
In theory, you could also use thinner sheet metal screws and attach everything with pre-drilled holes.

Thanks for the input!

The IKEA instructions state on the back that the back panel should be fixed with small screws rather than nails—probably to ensure better stability. Maybe sheet metal screws would actually be an option if they allow a smoother torque when screwing in and put less stress on the particle board?

However, others here say that 3.5 mm (about 0.14 inch) wood screws should also work.

My concern is that with sheet metal screws, I’d have to choose a length so they don’t go all the way through, right? Would 3 x 20 mm (about 0.12 x 0.8 inch) be sufficient?

Would you rather pre-drill the shelf board and use small wood screws, or is it also possible to screw directly into the back panel?

alberttau schrieb:
My concern is that I have to choose the thickness of sheet metal screws so they don’t go all the way through, right?

Exactly right, 3 x 20 mm (3/16 x 3/4 inch) screws could work if you screw them in carefully. A little tip: sheet metal screws essentially cut into the material, are very thin, so they usually cause minimal splitting.

Important: If you already have pre-drilled holes, avoid using sheet metal screws, as they tend to rub rather than cut and might damage the material. Pre-drilling is recommended only for wood screws.

And yes – always tighten with some care, you don’t want the back panel to crack immediately. 🙂