How to drill hole in metal stud for floating shelf?

[fiorella]

 I am drilling into a metal stud and noticed I've made two dents. Should I keep going? The hole is 10mm for a 4.5mm screw (I am aware that is too big and will repair accordingly).

I made the mistake of putting in a wall plug so the hole was already too big. I will either fill or use toothpicks for that but I'm worried about the metal stud.  Will this affect its structural integrity? Can I keep drilling? The drill bit also started wobbling which made me stop immediately. 

[MitchellMc]

Welcome to the Bunnings Workshop community @fiorella. It's a pleasure to have you join us, and many thanks for your question about attaching items to metal studs.

When attaching items to metal studs, you can either use self-tapping screws or expanding toggles. We don't use wall plugs for metal studs, they are only for concrete or brick walls.

I’d recommend switching to a self-tapping metal screw instead. These screws are designed to cut their own hole into the metal, so you don’t need to pre-drill a hole. This will provide a much more secure fit than trying to repair the oversized hole with fillers or wall plugs.

Please let me know if you have any questions.

Mitchell
 

[fiorella]

Thanks so much for your reply Mitchell 

Just to clarify I mistakenly at first used a wall plug (I made an x on spots to use a wall plug and a circle on spots I had to drill a pilot hole and I made a mistake)

I am a drilling pilot hole of 4mm and then using a 4.8mm metal screw (10g). The reason I am drilling a pilot hole is that it is  basically impossible to access the hole with the bracket I am trying yo attach to the wall, even when using ab extended drill bit.

My question is, is it OK to keep drilling the pilot hole of 4mm and use the 4.8mm screws? I am worried that the dents from the drill will make the pilot hole too big and the screw won't be able to grip 

[MitchellMc]

Hi @fiorella,

I somewhat understand your reasoning for drilling the hole, but metal screws need to cut their own holes, you can't pre-drill holes for them. There's no specified drill bit size for pre-drilling for a self-drilling metal screw. I can't guarantee that your 4mm drillbit won't remove excessive material causing the metal screw not to be able to grip adequately.

If you need to place a hole in the metal stud, use the screw without the bracket in place to create its own hole. It has a self-drilling head. In saying this, I presume you have room to drive the screw in once the bracket is in place. The normal method for attaching a bracket to a metal stud would be to put the screw into the hole of the bracket and then drive it into the metal stud.

It sounds like you might not be using a self-drilling screw designed for metal, but rather a metal screw designed for plastic or timber. Would you mind sharing a picture?

Mitchell

[fiorella]

Thanks for your reply
yes I can use a normal hand held screw driver to drive the screw in once the hole was pre-drilled. I could not use a screwdriver to drill the hole into the wall without a predrilled hole, I didn’t have the strength

if I use the screw to drill the hole without the bracket and then remove it won’t I loose grip with the stud? Would it still be able to hold the bracket up?

I’ve already installed 4 screws and brackets this way, would this be a problem?

[MitchellMc]

Just so we've both on the same page, those screws cut their own holes, @fiorella. If you would like a suitably sized hole for them in the metal stud, pop a Phillips head bit in your drill and drive the screw into the metal stud. You can then back it out again, and you'll have the perfect-sized hole.

Run the drill at medium speed, and it will take about 30secs for the screw to cut and drill its own hole. Typically you'd do this in one shot after you've passed the screw through the hole of the bracket, but I understand that might not be possible.

Mitchell

[fiorella]

Thank you for your reply,

My concern is that if I create a hole of the same size, the screw won't grip as tightly once I put it in again (hence using a smaller drill bit for the pilot holes). Would it still be able to grip the metal if both the screw and hole size are the same?

Also, does the fact that I already have two dents in the metal stud affect it?

[MitchellMc]

How much weight with the shelf be holding and how many screws are used for all the brackets @fiorella? If your shelf will be holding 20kg or more, which would typically be more than what a floating shelf can carry, I might have concerns. Anything around 10-15 kgs would be fine.

Drilling the hole with the screw and then backing it out might slightly reduce its gripping capacity. However, it cuts a hole smaller than the threaded section, and the threads cut their own way into the metal. When you re-insert the screw the second time it will self-thread into the metal. I've had to insert, remove and reinsert metal screws many times before without issue. The only time you really strip the hole out too large is when you drill the screw in right up to the head and then continue to drill. That wallows out the hole and might make it a bit too large to be usable again.

Now that I'm on the right page, can you not put the screw through the bracket and do this process in one go? Is the bracket obstructing the screw so badly that you can't use the drill and will have to use a small hand screwdriver to tighten them?

Mitchell

[fiorella]

Yes the bracket is obstructing the screw so badly it is impossible to fit the drill and only a small narrow screwdriver will fit. 

I also want to hang things from the shelf so I want it to be well supported. I have installed extra brackets and run some calculations so I think it will hold the required weight.

Thank you gor your insight about inserting and reinserting h metal screws, this places my mind at ease, and I will try again. 

I'm still concerned the dent will affect the structural intergrity, if you have any insight I would appreciate it, otherwise I'll give it a go 

FYI the shelf is 1.8m long, melamine. 16mm deep and 295mm width. The brackets come out 20cm and I've used 6 of them for this shelf.

Thank you!!

[MitchellMc]

That's a bummer; I've run into that issue many times before, @fiorella.

The only thing I could suggest is offsetting the bracket up or down slightly so you have fresh material to screw into.

Mitchell