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:
- http://nfaspace.com/services/Forms_files/Anchor Classification Guide.pdf
- https://anchors.dewalt.com/anchors/_documents/uploads/DWANF_ICDWANCHSG_r01.pdf?1659150839
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.
These anchors are designed to be tight in the hole before you even put a screw in. If it spins freely then the hole is too large and you need a larger anchor. When in the hole the anchor should fit fairly snuggly on it’s own.
Don’t worry too much about the specific model, as almost all of them have quite similar specs
Thanks! That answers my original question. 6 or 7mm will work according to this spec.
These are the worst possible wall plugs you could buy. Toss them and get better ones. I only use Fischer DuoPowers myself.
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.
It is really unclear what you mean by this.
Using these plastic anchors is basically a destructive process, so I don’t see an issue with the screw cutting into the plastic.
Another issue is often that you have hollow core bricks and thus the anchor ends up partially in the air, maybe double-check that this isn’t the case?
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.
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.
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.
The anchor spins freely in the hole, which I think is expected.
Sounds like your hole is too big, you normally want to start with the plug being an interference fit. Try tapping it in with something to take up the extra space around it.
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.
deeper hole, longer anchor (and longer screws) to take into account the ~10mm of plaster. If the brick is also soft your drill bit may be making a larger diameter hole than intended - careful drilling will be needed.
The anchor should be tight and need to be hammered in until the lip is flush with the surface.
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That looks like it’s for a hollow wall. The middle looks like it’s meant to bend to a huge diameter. If that were inside a brick hole, wouldn’t it just make around 1mm of contact at the point where it bends?
You are right; my mistake! I meant to suggest a wedge type that theoretically functions similarly to the one you posted, using friction between the anchor and the pilot hole, but is made of metal. An important variable I didn’t notice if you mentioned is how much weight you intend to hang. This is what I was imagining:
Make sure to get one that includes a masonry drill bit to remove the hole diameter guess work!
I think some of us are struggling when we see you wanting to use a plastic anchor in masonry. It just doesn’t make sense unless the load will be very low.
Even if the anticipated load weight is low: if you hang, say, a shelf on a brick wall, people who place things on the shelf in the future are likely to assume you used a stronger anchor than plastic.
Edit: I see in other comments you are plenty experienced on the topic of anchors. It seems the brick integrity is your big unknown variable. Maybe I would go with this type if I wanted to avoid chemical:
I have never had luck with those things. If I must use them I epoxy them in. Mostly though I use metal anchors in concrete.
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what instructions?
If there had been instructions supplied, do you think they would cover the scenario of 10mm of gypsum plaster rendered over brick?
