I used a 10mm masonry bit to drill for a 10mm plastic anchor like that pictured. The anchor spins freely in the hole, which I think is expected. I thought I read somewhere that the screw size should be 2mm less than the anchor. Thus 8mm for a 10mm ø anchor. But an 8mm screw is fat enough to rub sides of the anchor as it is inserted because I suppose the anchor is only 1mm thick at the opening. The guy at the shop confirmed that 8mm is too big. He said a 6mm screw matches and sold me those. After installing and loading, the anchor started to pull out.

Do I need a 7mm ø screw? Odd sizes get decreasingly common above 5mm. Yet 10mm sleeves are very common… so it’s not adding up.

I would like to have a reliable PDF chart of bore,anchor, and screw sizes – in metric. It seems there are plenty of such charts for Imperial/English units, like these:

I’m not sure what a “#10” screw or anchor is. Does that refer to the metric size despite being in an imperial system.

  • Uranium 🟩@sh.itjust.works
    0·
    8 hours ago

    As silly as it sounds, depending on what you’re wanting to mount you may be best off just either putting some paper/toothpick/matchstick (without the head) into the hole so the raw plug is tight enough that it won’t spin as you drive the screw in. (Would only suggest this if its for picture frames or similar weight)

    Out of curiosity is it plasterboard or brick that you’re trying to mount to?

    Raw plugs shouldn’t spin freely, you should need to gently tap them in with a hammer/wooden block/back of the drill, often its better to use a slightly smaller bit (9.5mm) particularly as the hammer drill setting will often make the hole just a tiny bit bigger or if drilling plasterboard as its so easy to make the hole too big