does using drywall anchors hold more weight than using plain screws?

18 views
0

If yes… how??

I’m currently in the process of hanging some furniture onto drywalls and was wondering about the claims on dry wall anchors to hold so-and-so amount of weight. Could someone explain to me the physics behind these things? I don’t get how dry wall anchors can claim this.

Doesn’t gravity and the quality/sturdiness of the wall and the thickness of the walls be what determines the weight capacity hanging on a point in the wall? How does putting a drywall anchor help other than preventing direct contact of the screw with the wall? I understand you would like to protect the hole in the wall from the sharp edges of a screw but do drywall anchors also ease the load off of whatever is hanging on it?

Tldr; would like to know the physics behind how drywall anchors.

In: 0

Drywall is very easy to break. If you mount regular screw you can pull it back with fingers because hole wals will vreak instantly. Drywall anchor works differently to normal anchors. They does not expand inside hole, they expand outside it from other side of wall. Thus firmly fixing for horisontal force. Only thing remains is not to apply to much vertical force by putting too heavy things, otherwise drywall will crumble.

Drywall is made up of a crumbly chalk like substance contained by thick paper. It doesn’t hold screws very well, and the narrow surface area of the screw will easily pull out of the relatively weak drywall.

A drywall anchor pushes through the wall and then expands to provide a much larger surface area for the screw to pull on. This more significant area is much more able to hold weight without ripping out

If we just look at the force required to pull out a screw the force will just be on the contact area of the threads on the drywall. That is not a lot so the force will get high and it is not hard to crush the material.

Drywall is not had or have long fibers, so when you crush it to dust that no longer gives any support. If you do that with wood what happens is a fiber that initiates bends and can still resist the skew until they are damaged too much. Wood is also flexible and can get compressed to some degree and press back on the scrrw

You can crush the material when you drive the screw in. Take an extreme case like if you screw on a metal plate that is thick enough and will not bend. If you do not stop when the plate is forced onto the wall by the screw the result of your turning the screw crush the wall material.

In a drywall anchor that is just a plastic cylinder the screw thread is on the plastic and is bent and gets deformed without getting directly crushed to dust. The force that stops you from pulling out the screw will be the friction along the edge of the hole. So the force will be on a larger area and you will not crush the drywall when you screw in the screw.

Acors that extend behind the wall will spread out the force over a large area too.

There are threaded drywall anchors to that look like very large screws made of plastic or metal. Larger threads spread out the force over a larger area and are separated so loss of material in between them, The large out flange on them makes it easier to install them without over-torquing them and crushing the drywall

Fore requirement for bending is not fundamentally any different, you spread out the force over a larger area and you can bend them more before they crush the drywall

Material strength is about pressure not force, if you’ve got a 50 lb force on a small area it can easy punch through drywall, but if you spread that out over a much larger area the drywall can hold it without issue

Anchors are all about getting more material in contact with the drywall to increase the area the force is applied over and therefore reduce the pressure on the wall

If you just put a #6 screw in the wall then the load you put on the end of it is trying to tilt it upwards in the wall. This puts all the load over an area that’s just 0.138″ (screw diameter) x 0.5″ (drywall thickness). With a 50 pound load that’s 724 psi and some sad drywall

If you use one of the big old screw anchors it results in the load being over an area that’s closer to 0.5″ x 0.5″ so now that 50 pounds is down to 200 psi

If you use one of the big ol’ toggler anchors now you’ve got a contact area closer to 0.5″ x 2″ because its just a plate on the back of the wall. Now you’re down to just 50 psi