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 (sometimes also written as “№10”). Does that refer to the metric size despite being in an imperial system?

(update)
The brick is rendered over with ~10mm plaster. The anchor is flush with the wall so about 10mm of the anchor is wasted. I think the anchor needs to be pushed in to be flush with the brick. But that’s a struggle. I think the proper approach is to screw in the screw just a couple rotations and then to hammer on the screw. But the anchor is either too big for the hole or something. The screw drives in but the anchor does not go with it. I think I will try softening the anchor with a heat gun and then try to push it in deeper. Or maybe I need a fatter screw just to drive the anchor in more.

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.

So one theory is that I need to drill 10mm deeper so the anchor can be flush with the brick not the (useless) plaster. OTOH, the collar of the ancher seems a bit useless anyway for about 10mm.

  • diyrebel@lemmy.dbzer0.comOPEnglish
    3·
    22 hours ago

    Why were you drilling if it’s an existing hole?

    It was not a freshly drilled hole. I would always use the same size bit as the anchor diameter so I remembered that. A 10mm anchor in a 12mm hole would also be very loose which is not the case here.

    I just now drilled a bit more after realising that the anchor should probably be flush with the brick, not the 10mm of plaster layered on top of it.

    You’re using a masonry bit with a hammer setting right?

    Yeah, and in fact it’s not just a hand drill with a hammer setting but a proper ~10kg hammer drill with a shock absorber, a grease reservoir, and STS mounted bits (or whatever they are called). Before I bought this big gear that makes me feel like Rambo, I used a standard drill with hammer setting on poured concrete and it melted one of my bits because it had a weak hammer and spun fast enough to make the bit molten red hot.

    I wouldn’t re-use this thing. This is the cheap type that comes free with things that need to be fixed to a wall.

    Maybe too late to change now but I might consider a different anchor if it fails to hold my bicycle. I ended up drilling 10mm deeper so that I could push the anchor to be flush with the brick (thus 10mm recessed below the plaster layer). I also added a metal shard about the size of a toothpick between the anchor and brick. It’s holding for now but does not feel rock-solid.