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I have a ceiling made of 12 mm thick drywall panels. The drywall itself is attached to metal profiles, but these profiles have holes every few centimeters. Now, I want to drill a small hole (6 mm) through the drywall (and potentially through the metal profile behind it, which is a few millimeters thick). It's not a problem if I hit the metal directly, as I can use a metal drill bit. If I don't hit any metal, it's even less of an issue. The problem arises when I hit the edge of one of the holes in the metal profile. The drill bit immediately slips because the drywall is very soft, and the hole becomes messy. What is a solution for this?

Here is a picture during the construction of the house some years ago. On the right you see the drywall panels of the ceiling and on the left you see the metal profiles below.

enter image description here

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  • which holes are you taking about?
    – jsotola
    Commented Jul 16 at 16:06
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    @jsotola, there are slots on the angled standoffs and holes on the mounting flanges. This is common with about any sheet metal profile used in residential construction, such as corner bead.
    – isherwood
    Commented Jul 16 at 16:08

3 Answers 3

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Use a guide of some sort to force the bit to remain in position, such as a block of wood. Pre-drill the block, then align the bit on the drywall. Hold the block in position while you complete the bore. Optionally stick the block to the drywall with removable foam tape.

Use light drill pressure to give the bit time to cut without displacing the metal channel. It can also help to start with a small bit and work up. 6mm bits will not cut through sheet metal very well if there's flex. You'd want to have holes in the guide block for each bit size.

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Start with a smaller bit

1/16" bits are cheap and they make small holes. They're ideal for when you need to explore behind the wall. Any slips are much easier to patch. Hopefully you don't have a textured ceiling. If not, you can spackle and paint them easily.

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  • Protip: In order for this to work you need to use high speed and low force. Pushing too hard will still result in the bit glancing off and possibly breaking. It's still unlikely to work well on the angled shoulder of the profile.
    – isherwood
    Commented Jul 17 at 13:42
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When in doubt - cheat!

enter image description here

Use a pin punch, a nail, or a center punch like this straight up through the drywall. Probe around until you're sure the point is on the metal railing, then add a dent with a hammer or pushing the punch.

Then use your normal drill to go straight up, and the dent/divot/punch mark will keep it on center.

Other things to help enable success:

  • Don't be leaning off a ladder - make sure you have good steady foot placement. For a big job, a scaffold can make life easier.

  • Use a good drill - mains powered or with a hot battery. If the battery is getting low, stop for a recharge rather than pushing on.

  • Goggles or similar - there will be metal swarf dropping right on you. This is no fun in the eyes.

  • Use a good drill bit. Either sharp, or one of those pyramid-tipped bits can help immensely. Not a cone or stepped drill - this kind of bit:

enter image description here

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  • This isn't going to do much. Those channels are often mounted on just one edge, so there's a lot of flex in the channel. The force it takes for an automatic center punch to actuate will bend things around. Also, the problem posed is on the sloped edge of the channel. so the punch will slide off just as the bit does. Pilot point bits have the same problem as smaller bits would.
    – isherwood
    Commented Jul 17 at 12:38

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