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.

  • OfCourseNot@fedia.io
    0·
    3 hours ago

    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.

    First mistake. For crumbly material you should use a 9.5 or a 9. The plug should fit tightly, as tight as possible while still getting in with some gentle hits with the butt of the screwdriver or even a hammer.

    The screws are alright, I guess. For a 10mm plug, you’d use 5-7mm screws (read the instructions on the packaging, sometimes on the plug itself). It should be at least a bit longer than the plug, and the hole a bit deeper than the screw length.

    Now there might be a solution to the hole too wide. You need to get the screw a bit screwed in, as it gets in the plug will spread and hold to the wall. If you can do it with the plug out of the wall it’ll be easier, depending on what you’re fixing to the wall and how, once it opened a little and it’s a tight fit, hit them all together (with any braces or whatever that needs to be with the screw) into the hole until the plug is flush with the wall, screw it all the way in, and then tighten it. If you cannot and you have to do it with it in the wall, another trick is to try screwing in the screw with fast, short bursts (hand screwdriver or electric / power drill). If the plug don’t even have enough grip for this and it keeps spinning in the hole, try to keep it from moving with the tip of a small flat screw driver or electrician scissors, once the screw is going in it’ll start to hold by itself.

    The part where you tighten it after the screw is all the way in is important. This makes the screw pull from the end/middle of the plug and deforms it, shaping it to the hole so it gets a proper hold.

    The problem is worsened by the fact that as I screw, the anchor is coming out by about 5mm. So it’s even shallower than when I start screwing.

    (update 2)

    Now I see why I cannot get the anchor to be flush with the brick: I only drilled the hole deep enough for the anchor to be flush with the plaster layer.

    The plug doesn’t need to be flush with the brick, you can see that part of the plug is completely flat and smooth, and doesn’t make anything for support or grip, is there because of the plaster. The hole needs to be deep enough for the screw tho, or it will push the plug out.