Understanding PULL STRENGTH & PARALLEL HOLD is key when choosing a magnet.
Reviewed in the United States on September 17, 2019 | Rating: 4/5 | Best Sellers in Industrial & Scientific
the 22 lb magnetic hooks i bought are no longer listed in the ad  they are now selling 25 lb hooks instead  just something to keep in mind when reading calculations based on the 22 lb hooks i bought   reviewed below  among other things im using these on three steel doors to hold the curtain rods that hold the curtains  they are quite strong for their size base is 12 in diameter and im very happy with their parallel holding power  i docked one star for two hooks that dont fit in their base demoting them to refrigerator magnetssimply put a magnets pull strength  measures in kilograms or pounds the amount of vertical force  required to pull the magnet away from the metal surface it is stuck to  applying that to these magnetic hooks means that each one when stuck to a metal ceiling is rated for a maximum holding power of approximately 22 lbs10 kg before it will pull away from the ceiling assuming all conditions are idealtake the same magnetic hook and put it on a wall made of exactly the same material as the ceiling and it will slide down the wall much easier than it will pull away from the ceiling or pull away from the wall for that matter  this is the magnets parallel hold or shear force and its not nearly as powerful as its pull strength  this same concept explains why 2 magnets stuck together are easier to separate if you slide them apart than if you try to pull them apartmanufacturers are generally referring to  pull strength  when stating the holding power of a magnet  pull strength is determined by the maximum amount of weight a magnet held when tested under ideal conditions  parallel holdshear force can be reasonably estimated at 10 to 25 of a magnets pull strength  with that in mind well assume a parallel hold of 17 for these magnetic hooks rated at 22 lbs 22lbs x 17  374 lbs  under that assumption we can expect that each hook if used on a metal wall or door should hold approximately  3 34  lbs of weight before it slides down the wall  obviously thats much less than its stated pull strength of 22 lbs the amount of weight it should hold if used on a ceiling  because a magnet fails under less weight when used on a wall rather than a ceiling or holds less weight than stated on packaging or sale ads does not mean that the magnet is flawed or the manufactuer and sellers are deceitful  the magnet is simply demonstrating in real life and perhaps to the users dismay the difference between its pull strength 22 lbs in this case vs its parallel holdshear force approximately 2 14 to 5 12 lbs  10 to 25 of 22 lbsin addition to orientation there are other factors or conditions that influence a magnets performancestrengthholding power such asthe magnet  what is the magnet made of what type of material  ceramic alloy rare earth etc  what is the magnets condition  chipped cracked scratched dirty etc  what is its size and shape  is the magnet cupped or not  cuppedmagnet is placed into a steel cup or holder like the  magnets on these hooks  cupping focuses most of the magnets pull in one direction the open  end of the cup giving it more holding strength than it would have without the cup  how has the magnet been handled  has it been stored correctly it matters  has it been dropped dropping magnetnot goodenvironmental  what is the ambient temperature and humidity level  is there excess moisture present  will the magnet be completely submerged used to attract submerged items  what is the temperature of the metal the magnet will attach to  what is the temperature of the magnetthe metal  what of the metal the magnet attracts or attaches to  how thick is the metal  thicker  better  what are its components  what is the condition of the metal item or surface  is it bare and clean or is it coated painted dirty greasy rusty  is it perfectly flat or is it curved or uneven  is it perfectly smooth or is it textured rough bumpy dented chippedanything that interferes with 100 full  direct contact between magnet and metal diminishes the magnets holding powerand thats just the short list theres more and it all mattersi think the physics of magnets and magnetism is fascinating but technical and complex enough to blow my  mind right out of the science book  fortunately for most of us average consumers this very basic understanding of pull strength as it relates to parallel holdshear force is likely the most beneficial and easiest to remember when choosing a household craft hobby or shop magnet for your particular task  note  ideal conditions for testing a magnets holding power means the metal is thick perfectly smooth and flat perfectly clean and bare same for the magnet it is in perfect new condition  ambient conditions temp humidity dustfree etc are also perfect  everything is as perfect as it can be in order to achieve the maximum holding power of the magnet and that result is what is stated on packaging in ads etc  our personaluse conditions are very unlikely to be as perfect as testing conditions and a magnets strengthperformance will be affected accordingly