Shelves

SavingStudent1

FreeBear said:

SavingStudent1 said:  - Choose the drill bit according to the wall plug thickness, make sure you drill a hole 1 mm less or of the same thickness. So, if we choose a brown wall plug ~ 7mm, start off with a smaller drill bit of 6 mm and if the wall plug doesn't fit, then re-drill the hole using 7 mm thickness drill bit, but never larger than the wall plug thickness.

When drilling holes, I'll often start with a 3mm or 4mm drill - It makes it much easier to get the hole on the mark. Go in with a 6mm drill to the full depth required, and then use a 7mm to bring it to size. Trying to do it with just a 7mm drill (or even a 6mm) invariably means the hole ends up being in the wrong place and bigger than intended.

Oh right, so you always start with a small drill bit to get the hole where you want it. Then, once you drill an inch or so in, you then got it in the right place and now take the larger drill bits closer to the size desired to drill it to the full depth, and then finish it with the correct drill bit size to get the desired thickness.

Is this the idea?

FreeBear

SavingStudent1 said:

FreeBear said:

SavingStudent1 said:  - Choose the drill bit according to the wall plug thickness, make sure you drill a hole 1 mm less or of the same thickness. So, if we choose a brown wall plug ~ 7mm, start off with a smaller drill bit of 6 mm and if the wall plug doesn't fit, then re-drill the hole using 7 mm thickness drill bit, but never larger than the wall plug thickness.

When drilling holes, I'll often start with a 3mm or 4mm drill - It makes it much easier to get the hole on the mark. Go in with a 6mm drill to the full depth required, and then use a 7mm to bring it to size. Trying to do it with just a 7mm drill (or even a 6mm) invariably means the hole ends up being in the wrong place and bigger than intended.

Oh right, so you always start with a small drill bit to get the hole where you want it. Then, once you drill an inch or so in, you then got it in the right place and now take the larger drill bits closer to the size desired to drill it to the full depth, and then finish it with the correct drill bit size to get the desired thickness.

Is this the idea?

Yup. Spot on.

SavingStudent1

FreeBear said:

SavingStudent1 said:

FreeBear said:

SavingStudent1 said:  - Choose the drill bit according to the wall plug thickness, make sure you drill a hole 1 mm less or of the same thickness. So, if we choose a brown wall plug ~ 7mm, start off with a smaller drill bit of 6 mm and if the wall plug doesn't fit, then re-drill the hole using 7 mm thickness drill bit, but never larger than the wall plug thickness.

When drilling holes, I'll often start with a 3mm or 4mm drill - It makes it much easier to get the hole on the mark. Go in with a 6mm drill to the full depth required, and then use a 7mm to bring it to size. Trying to do it with just a 7mm drill (or even a 6mm) invariably means the hole ends up being in the wrong place and bigger than intended.

Oh right, so you always start with a small drill bit to get the hole where you want it. Then, once you drill an inch or so in, you then got it in the right place and now take the larger drill bits closer to the size desired to drill it to the full depth, and then finish it with the correct drill bit size to get the desired thickness.

Is this the idea?

Yup. Spot on.

Thanks, this is so helpful. I need to first get a drill and experiment as I am always so scared of the thought of it going wrong, without even trying!

grumbler

Beware, that many (most?) masonry drill bit sets for some mysterious reason don't include 7mm.  So, if you chose brown plugs you'll probably have to buy 7mm separately. It's not expensive, but can cost you an extra travel to a shop if you don't check.

SavingStudent1

Bendy_House said:

SavingStudent1 said:

Bendy_House said:

All good info above.

The sequence in choosing these sizes of fixings will start with the screw - how thick does it need to be? Usually 4 to 5mm will cover most bases. You then choose the plastic plug to suit the screw, and the masonry drill bit to suit the plug (the plug will state all the sizes it'll cope with).

For your shelf, the sizes suggested above - ~4.5 to 5mm screws with brown plugs sound good.

The screw should go roughly 2" into a solid wall, maybe slightly less. That means the hole to be drilled should be a bit deeper again - by at least 5mm or more, since the screw must not bottom-out.

The plug should be inserted well into the hole, certainly below surface level. The layer of plaster (~half-inch) over the blocks won't be doing much of the holding, and is also prone to crumbing around the hole if the plug is too near the surface and expands there when the screw goes in. So, drill the hole the required depth (wrap tape around the drill bit as a depth-gauge), insert the bare screw and use it to catch and remove all the dust and debris in the hole (or use a straw to blow it clean, but close your eyes...), and then insert the plug and tap it down until flush with the wall. Place the screw in it, but don't turn it. Gently tap the end of the screw to try and get the plug as far into the hole as you can, ideally a good few mm below surface level at least.

Screw. The screw should feel firm to turn once it's getting over half-way in there - that's the sign of a good grip. If they are tight to turn, then coat the screw thread with oil - even cooking oil.

First, tho', mark out carefully and level where - exactly - the holes need to be drilled. You can use a screw & hammer to tap a wee starting dint in the wall - the drill bit will be less likely to wander. Hold the drill level, and nicely firm so you are preventing it from wandering under its own weight. If you find that the drill wanders off course once it hits the blocks under the plaster layer, it may be that the concrete used is just too hard (pebbles, etc) for a normal hammer drill. An SDS drill (from around £50) will make easy work of this.

Thank you, this really helps.

1. What do you mean by "screw must not bottom-out"? The screw tip mustn't reach the bottom of the hole before it's done its job - securing whatever. If the screw tip hits the bottom of the hole, then (a) if cannot go any further so you may not be able to tighten up whatevere it is you are fixing, and (b) it'll try and force out the plug by it being 'screwed' back up the screw shaft.

2. What do you mean by "surface level" in this context? The top surface level of the wall. The best part of 10-15mm depth of what you see in front of you will be plaster. Plaster isn't that strong, so however much of the plastic plug remains in that layer won't be doing much holding. If you insert a 40mm-long plastic plug into a solid wall like yours, and stop when the top edge reaches the wall surface, then ~15mm of that plug will still be in that plaster layer, and only 25mm will be soldily located in the hard block wall behind it. 25mm isn't much, at least not if you want a really firm fixing. So, for a 40mm plug, drill the hole a good 60+mm deep, clean out the hole, and try and tap the plug right in so it's well below surface level.

3. Should the hole be drilled 5 cm (I assume you meant cm instead of mm) deeper than the length of the screw or the wall plug? If you drill the hole 5cm (50mm) deeper than the screw length, then chances are you'll end up in the next room. So, yes, I did mean drill the hole around 5mm MORE than the max distance the screw will go in. After you drill the hole, place the screw fully into it (without the plug). You want the screw to either go all the way in so the screw head lands on the wall surface, or you at least want the screw head to be sticking no further out than when it's actually doing its intended job. For instance, if you were going to be screwing a timber batten to the wall, and this batten was 20mm thick, then the screw would have to be able to sit in that hole will only 15mm at the very most sticking out. If the screw bottoms out with 20mm of it still sticking out of the wall, clearly it ain't going to be holding that batten tightly to the wall.

Thanks for the tips regarding the drill wandering, this was one of my main concerns as I don't want to drill a line instead of a hole lol. 'Welcome :-)

Replies in bold.

Thanks, so just a few follow-up questions:

Okay, so we have a scenario where the hole will be 60+mm deep and the wall plug will be fully inside the wall, as in your won't be able to see it at surface level as it'll be completely inside the hole. I don't know why I always thought, you should only push the wall plug until it is fully in, but its top edge reaches the wall surface and so you can see its exterior. But yes, in that case, there will be a gap between the end of the wall plug and where the hole ends because it is much deeper, and most of it will be covering the plaster layer.

Ok, so 5 mm lol not cm, as I don't want to go into the next room

SavingStudent1

grumbler said:

Beware, that many (most?) masonry drill bit sets for some mysterious reason don't include 7mm.  So, if you chose brown plugs you'll probably have to buy 7mm separately. It's not expensive, but can cost you an extra travel to a shop if you don't check.

Oh right, thank you for the heads-up, I will have to take this into consideration.

Bendy_House

SavingStudent1 said:

Thanks, so just a few follow-up questions:

Okay, so we have a scenario where the hole will be 60+mm deep and the wall plug will be fully inside the wall, as in your won't be able to see it at surface level as it'll be completely inside the hole. I don't know why I always thought, you should only push the wall plug until it is fully in, but its top edge reaches the wall surface and so you can see its exterior. But yes, in that case, there will be a gap between the end of the wall plug and where the hole ends because it is much deeper, and most of it will be covering the plaster layer.

Ok, so 5 mm lol not cm, as I don't want to go into the next room

If you look at these plastic plugs, they tend to be - what? - around 45mm long? And yet they will be used with screws of various lengths, 3", 4", more sometimes.

That's ok. As long as the plug is sitting snugly in the most solid part of the wall, it doesn't matter if a long screw goes right through it and out t'other end. ~45mm of that screw's threaded shaft will still be biting firmly in that whole plug, so it shouldn't be going anywhere.

If you were drilling into a bare concrete block or brick - ie no plaster or p'board layer - then you'd simply tap the plug until it's flush, and then a few mm more so's the end is just below the surface level. When you have a layer of something on top of the solid block/brick - plaster or p'board - then just keep in mind that this upper layer does not have much strength or purchasing power, so you really want the plug tapped in further so's it's in the 'solid' hard bit.

Also, the very top surrounding edge of the hole you've just drilled will be relatively weak, so if the plug is just 'flush' with this, don't be surprised to see some light crumbling around the hole as the screw goes in and squeezes the plug outwards. This is normal, and shouldn't be a problem (unless large chunks break away...), but it's another reason why I always tap the plugs to below surface level.

And one other reason - if you just push the plug in until it's 'flush', then if the plug moves during the screwing process and even comes out a couple of mm, that couple of mm will prevent whatever you are screwing to the wall from sitting tightly against it.

Man, I didn't know there was so much info regarding plugs and screws...

SavingStudent1

Bendy_House said:

SavingStudent1 said:

Thanks, so just a few follow-up questions:

Okay, so we have a scenario where the hole will be 60+mm deep and the wall plug will be fully inside the wall, as in your won't be able to see it at surface level as it'll be completely inside the hole. I don't know why I always thought, you should only push the wall plug until it is fully in, but its top edge reaches the wall surface and so you can see its exterior. But yes, in that case, there will be a gap between the end of the wall plug and where the hole ends because it is much deeper, and most of it will be covering the plaster layer.

Ok, so 5 mm lol not cm, as I don't want to go into the next room

If you look at these plastic plugs, they tend to be - what? - around 45mm long? And yet they will be used with screws of various lengths, 3", 4", more sometimes.

That's ok. As long as the plug is sitting snugly in the most solid part of the wall, it doesn't matter if a long screw goes right through it and out t'other end. ~45mm of that screw's threaded shaft will still be biting firmly in that whole plug, so it shouldn't be going anywhere.

If you were drilling into a bare concrete block or brick - ie no plaster or p'board layer - then you'd simply tap the plug until it's flush, and then a few mm more so's the end is just below the surface level. When you have a layer of something on top of the solid block/brick - plaster or p'board - then just keep in mind that this upper layer does not have much strength or purchasing power, so you really want the plug tapped in further so's it's in the 'solid' hard bit.

Also, the very top surrounding edge of the hole you've just drilled will be relatively weak, so if the plug is just 'flush' with this, don't be surprised to see some light crumbling around the hole as the screw goes in and squeezes the plug outwards. This is normal, and shouldn't be a problem (unless large chunks break away...), but it's another reason why I always tap the plugs to below surface level.

And one other reason - if you just push the plug in until it's 'flush', then if the plug moves during the screwing process and even comes out a couple of mm, that couple of mm will prevent whatever you are screwing to the wall from sitting tightly against it.

Man, I didn't know there was so much info regarding plugs and screws...

Haha, yeah so much info! Thank you so much, really appreciated, honestly!

getmore4less

for more information of fixings fitting and their loads try this

https://www.rawlplug.co.uk/wp-content/uploads/2020/03/Rawlplug_catalogue_Specification_Design_Guide_2020_compressed.pdf

page 263 deals with lightweight plug fixings.

edit :
this one that has easier to understand load data

https://timco.co.uk/Content/Images/uploaded/Brochure PDF/03.Anchors_web.pdf

The brown plug is good for 0.5kN tensile(pull out) in concrete(brick will be similar) if you get it right.