ᐅ Finding the Right Screws for Your BILLY Shelf – How Should I Proceed?

Thank you for the detailed answer.

The shelf has the standard hardboard back panel from IKEA, and I want to use the original shelves. I’m also wondering if the screws for the side panels and the screws for attaching the back panel are different, or if the same screws can be used for both?

Additionally, this shelf has those small metal pins that the shelves rest on, which are often found in IKEA shelves. However, the holders themselves are partly damaged, so I want to secure the shelves further with screws.

Are there differences in the type of screws between "securing the shelves" and "fixing the back panel"? I want to avoid the screws loosening under the weight of the books or the board splitting.

Jonbla50 schrieb:
I also have these small metal pins on the shelf, which the boards rest on

This is an important detail. The metal pins are designed to support the shelves only, not to screw them in place. If they are damaged, I would recommend replacing them first, as they provide horizontal stability.

Jonbla50 schrieb:
Are there differences in the type of screws used between "securing the shelf" and "attaching the back panel"?

Yes, definitely. For the back panel, IKEA usually uses very thin nails or special thin screws, since the back panel mainly serves as stabilization. Screws that are too thick or too long can damage the panel.

For the shelves, you should use slightly stronger wood screws, size M4, with a straight countersunk head, that are screwed into the side panel. Make sure the screws are not too long to avoid splitting the wood.

If you want to be on the safe side, buy screws with fine threads (sheet metal screws are not suitable), as this significantly improves holding power. Your idea to use fixed screws in addition to the pins for more stability is good, as long as the screws are chosen correctly.

For the shelves: Use M4 countersunk screws, length 30-35 mm (1.2-1.4 inches).

For the back panel: Use very thin screws or preferably nails, no longer than 20 mm (0.8 inches), otherwise you will damage the board.

Original screws are usually not sold individually, but you can find furniture screws with the same dimensions at hardware stores.

fajan schrieb:
If these are damaged, I would recommend replacing them first because they provide horizontal stability.

I have actually already replaced the dowels, but I want to additionally secure the shelves with screws because I am building the shelving unit quite tall and want to make it a bit safer, beyond the support provided by the metal dowels.

Johnathon schrieb:
Are there any special features in your shelving material or construction? For example, are you using DIY shelves?

The shelves are original, so not self-made. I’m just unsure if I should use fine-thread screws instead of coarse-thread wood screws because the fiberboard panels might swell or split. What do you think?

Jonbla50 schrieb:
I'm just not sure whether I should use wood screws with coarse threads or finer threads,

That’s a very good question, as the type of threading does indeed affect how the material behaves.

Coarse threads on wood screws provide stronger grip in wood, especially in softwoods or wood-based panels, because they displace more material and anchor better.

Fine threads are better for metal or very hard materials, but in chipboard or fiberboard, fine threads can easily cause splitting since the threads are too tight and don’t allow for relief.

My advice: use wood screws with coarse threads and pre-drill holes slightly smaller than the screw diameter. This prevents splitting while still ensuring a secure connection.

Pre-drilling is the most important factor, regardless of screw type. Ideally, the hole should be 2–3mm smaller than the screw diameter, depending on your screws.

If you screw without pre-drilling, the risk of splitting increases significantly, especially with fiberboard.

If you’d like, I can provide exact measurements for pre-drilled holes and screw selection.

Johnathon schrieb:
Use wood screws with coarse threads and a pilot hole slightly smaller than the screw diameter.

The tip about the pilot hole is really helpful, thanks! Would you recommend drilling the hole perpendicular or slightly angled to improve stability? Also, when choosing screws, are there specific materials like stainless steel or galvanized screws that work better for indoor furniture?

I’m also curious if self-tapping screws could be an alternative in case I don’t get the pilot hole perfectly every time.