Magnet Pull Force: How Much Weight Can a Magnet Hold
Determining the strength of magnet can be a complicated measurement. One common rating you’ll see on our Neodymium magnets, ceramic magnets and magnet assemblies to help determine a magnet’s strength is its pull force.
What is Pull Force?
A magnet’s pull force is the force that’s required to pull that magnet straight free vertically from a steel plate. It is usually measured in pounds and is a reliable method of measuring the magnet’s maximum strength. It also tells you the limit of that magnet’s holding power. The higher the pull force, the greater the strength of the magnet. Any magnet with a pull force over 7 pounds has the ability to pinch fingers and should be handled carefully.
What Effects Pull Force
Pull force seems like a straightforward measurement. It allows you to determine how much weight or tension a magnet can hold, but unfortunate it isn’t always that simple. There are a few things that can affect a magnet’s pull force.
Horizontal vs Vertical Placement
Pull force is the force that’s required to pull a magnet away from a steel plate vertically, such as from the underside of a steel beam or table. If you aren’t using your magnet in a vertical application, but in a horizontal application, such as to the front of a refrigerator or filing cabinet, it will not hold its listed pull force. The magnetic force will pull the magnet straight towards the steel door as gravity tries to pull the magnet down to the floor. Friction between the magnet and door is what prevents it from sliding all the way down to the floor. This is referred to as shear force. It will have a much smaller maximum value, somewhere between 15 and 30% of the pull force, but is too difficult to predict as there are too many variables between the two materials and any lubrication there might be on the surfaces.
When measuring pull force, a thick, completely flat, solid steel plate is used. The plate is larger than the magnet being tested, so that the magnet makes complete contact with the plate. This is, however, rarely the case in a real-life application. Differing thicknesses of steel (particularly less than .5 inch), the composition of the steel, coatings on the steel and uneven surface area, such as rust can all affect the pull strength of a magnet.
The distance between your magnet and the steel substrate you are attracting it to, can make an unbelievable difference in pull strength of the magnet. This distance is called an air gap and it refers to anything that comes between your magnet and your magnetic receptive material. It can include paint, coatings, paper and even grease or fingerprints.
Choosing the Right Magnet
There are many variables that can affect magnet pull strength which can make it difficult to determine the right magnet for your specific application. The best and only real way to know how it’s going to hold is to test the magnet in your application. If you have any questions, would like to request samples, or need help determining what magnet you need, you can always contact our magnet experts. We are happy to help you select the proper magnet for your application. You can call us at (800) 330-1432 or send us a message online.