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.

  • diyrebel@lemmy.dbzer0.comOPEnglish
    0·
    8 hours ago

    Using these plastic anchors is basically a destructive process, so I don’t see an issue with the screw cutting into the plastic.

    I don’t care about the plastic but my concern is that I would make it so tight that it cracks the brick.

    Another issue is often that you have hollow core bricks a

    I’m sure the bricks are solid; likely 150+ years old, back when all bricks were solid. But since they are old, they are probably fragile despite being solid.

    • poVoq@slrpnk.netM
      0·
      8 hours ago

      Hmm, yeah. Old burned bricks can be too powdery for regular anchors to hold well. There are anchors meant to be used with an special putty you put into the hole first and which seep into the brick to some extend.

      • diyrebel@lemmy.dbzer0.comOPEnglish
        0·
        7 hours ago

        Sounds like chemical anchor, which is a 2-component epoxy. I used that when installing anchors on my roof to use for abseiling. Did that because my life depended on it. But otherwise I try to avoid chemical anchors indoors because they cannot be removed later. I could get out an angle grinder at that point, but there may be a day when I decide to remove all the render to expose the natural brick, in which case the anchor would always be an eyesore.

        Otherwise I quite like chemical anchors because there is less stress on the wall, and yet they are stronger than mechanical anchors.