|Originally posted by ericeash
just wondering what the point of the plastic inserts is then, or for that matter, what the point of putting any screws at all in your walls or ceilings is?
This is some info from the "This Old House" site.
"Expanding Plastic Sleeves
Available in several varieties, these work well for light and medium loads Anchors like the blue version don't expand enough to grab well in drywall; they work better in plaster and best in masonry. Anchors designed to spread their "wings" are less susceptible to withdrawal."http://www.thisoldhouse.com/toh/prin...203389,00.html
Now bear in mind this is also info for things that you want to hang on walls and not ceilings. As hanging a item on a ceiling offers even less weight holding as it don't have the support of the wall itself when doing it that way.
"For example, you might successfully hang a 25 lb wired mirror onto a screw in a plastic expansion anchor (in drywall) where the force in downward. The same anchor and screw might not be able to support a 25 pound cabinet if the cabinet tends to pull the anchor outward. It's all relative. Strength, that is."
"All anchors can be divided into two basic types... expansion anchors and hollow wall anchors.
1) Expansion anchors are used in thick, solid materials... concrete, brick, mortar, metals or even wood. They work by expanding when a screw or bolt is threaded into them. If you remember anything about expansion anchors, remember this...
Expansion anchors are only as strong as the
material they are installed in.
If an expansion anchor is installed in a soft material (such as drywall), it may appear to be strong but don't be fooled... the strength is minimal and it will eventually loosen and/or pull out if too much stress is put on it.
2) Hollow-wall anchors, on the other hand, will not work in solid materials. Instead, they are designed to be used in thin materials or on hollow walls. They each have a unique way of spreading within the hollow of the wall. Once spread, the anchor cannot be pulled back through the smaller installation hole. The strength of a spreading anchor is proportional to the size of the "spread"!"
This info and more, is all fromhttp://www.naturalhandyman.com/iip/i...infanchor.shtm
And I just love this description for this one type of plastic anchor.
These conical plastic anchors are worthless for drywall. A #10 screw directly into the wall will work as well. (They work OK for light duty in masonry)"
This is from.http://www.factsfacts.com/MyHomeRepa...lfasteners.htm
Which also has a section on the strength of fasteners and how to calculate and how to use them for weights.http://www.factsfacts.com/MyHomeRepa...rstrengths.htm
Also many manufacturers of projectors, also recommend the use of a "safety cable", in addition to just mounting the projector with a normal mount.
And for you and some other people that may live in a earthquake zone. Here is some earthquake info for securing things, and also information of how things must be done when mounting all sorts of items in the schools in California that are also in such earthquake zones.http://www.oes.ca.gov/Operational/OE...sf/PDF/SB1122/