Magnet FAQ
1. What is the Pulling Force of a Magnet and How to Choose a Magnet Based on its Pulling Force for My Application?
Pulling force is one of the measuring methods to rate the strength of a magnet. It is typically defined as the force to separate the magnet from a low carbon steel plate for a direct touch and direct pull condition, where the steel plate should be 20 mm ( 0.787" ) thick. The steel plate surface should be smooth and clean. The force to pull off the magnet should be perpendicular to the surface.
Based on these factors, the pulling force will be smaller for any of the following situations,
- The magnetic surface is less magnetic than low carbon steel
- The magnetic surface is thinner than 20 mm ( 0.787")
- The magnetic surface is rough or not directly touched. For example, the surface is painted or there is debris on the surface
- The pulling force is not perpendicular to the surface. For example when hanging an item on the fridge
In most applications, the actual pulling force is smaller considering these factors.
Unlike Gauss and Maximum Energy Product, which are more scientific terms, the pulling force is used more often by amateur applications in choosing magnets. For example, choosing a magnet for crafting, office, home etc., where the actual pulling force is the basic concern.
2. What Decides the Pulling Force of a Magnet? To Increase the Holding Force, Do I Increase the Magnet Thickness or Width?
The Pulling Force of a magnet is decided by the Gauss ratings and the geometry parameters of the magnet. The higher the Gauss rating the greater the pulling force for the same size magnets. The Gauss rating is decided by the material the magnet is made of and the grade. For example, for the neodymium magnets, the greater the N number, the higher the Gauss rating. So the grade N52 has a higher Gauss rating than N45, so is the pulling force for the same size magnet.
Increasing the thickness of a magnet is more preferable than increasing the width. Generally speaking, the Pulling Force is proportional to the the thickness of the magnet and the area of the touching surface. So increasing the thickness is better than increasing the width unless the thickness is equal to or greater than the width.
Choosing a round Magnet is more preferable than choosing a rectangle magnet. Since a circle has a larger area than a rectangle given the same perimeter, choosing a round magnet will get a stronger magnet than a rectangular one for the same magnet weight.
In the conclusion, choose the magnets in the following order,
- Choose a round magnet over a rectangle magnet if a round magnet can be used
- Increasing the thickness before increasing the touching area unless the thickness is equal to or greater than the width
3. Do I Choose North Pole or South Pole for the Countersunk Magnets or the Magnets with Adhesives?
Different poles attract and the alike poles propel.
- When you are planning to use these kinds of magnets in pairs, choose half of your order North pole and the rest half of your order south pole. so they can pair up.
- When you are planning to use these kinds of magnets to a magnetic surface, either North or South pole would work. So choose no preference on the polarity.
- When you are planning to use these kinds of magnets to a magnet you already have, you need to find out which pole your magnet will attract to these magnets then choose opposite polarity of these magnets to match up.
4. What Type of Permanent Magnets Should I Choose for My Application?
There are varieties of permanent magnets available on the market per material and format so choosing a right magnet sometimes is a little confusing. The decision tree will help you to make the right decision.