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K&J Magnetics now offers several sizes of disc magnets with pre-applied adhesive. Read more to learn how these magnets can save time, especially for use in printed materials, folders, boxes and other magnetic applications.

Neodymium magnets are often used as magnetic closures for folders, printed materials, boxes and more. We now offer a few of our most popular sizes with adhesive backing pre-applied.

Using pre-applied adhesives helps take some of the variation out of glue joints, usually resulting in a better, more consistent bond. It also saves a lot of time, especially if you're making a large quantity of them.

## Magnetic Closure for a Folder or CD Case

To highlight a common use for these magnets, we constructed a CD case out of card stock material. Actually, we sacrificed a file folder that we had on-hand. The folder used for this example measures 0.010" thick, about as thick as 3 pieces of normal office paper.

In the video below, we show a blue CD case made with a 3/8" diameter D61AD-P magnet pair. The yellow CD case used the larger, 1/2" diameter D81AD-P magnets, but seemed too strong for this application with this card stock thickness. Note how the flap bends at around 0:22 in the video.

## CD Case Construction

How did we make the CD case? This 3 minute video below shows how!

## What size magnet should you use?

There are 2 important factors to consider: How much pull force can you expect from a given pair of magnets, placed a certain distance apart from each other? How much attractive force is needed in your application?

The distance between the magnets usually controls the magnetic strength you'll see. In our CD case example, two layers of 0.010" thick cardstock separate the two magnets. The magnet-to-magnet distance is 0.020".

How does this distance (the total material thickness) affect the strength? The farther apart the magnets, the weaker the attraction force.

For more technical answers, try using our Magnet Calculator to see how the strength is reduced. For a pair of our D61AD-P magnets, they pull with about 2.12 lb when touching each other. With a 0.020" wide gap between the magnets, the calculator suggests that the force drops to about 1.19 lb, just over half of the full strength!

You also have to somehow estimate the strength you need. In this application, this strength of just over 1 lb felt about right. Trial and error works -- getting a few magnets in your hands and trying it out is often the surest, quickest path to a good solution.

## How about a matching steel piece?

These magnets are sold in matched pairs. Can you use one of these magnets attracting to a steel piece? Yes you can, but it will behave a little differently. K&J Magnetics does not offer matching steel parts, but we can offer some advice about using these magnets this way:

1. If you replace one of the magnets with an identically sized steel slug, the attraction will be weaker than a magnet-to-magnet pair.
2. When reaching across a gap, a pair of magnets offers more strength than a single magnet to a steel plate.
3. For best results with a steel plate, consider sizing the steel plate a little bigger than the magnet for better strength. Use steel that is at least 1/32" thick.
4. Unlike a magnet-to-magnet attraction, a magnet-to-steel setup won't pull to center themselves on one another. You won't see that automatic centering action. On the plus side, a steel surface can be more forgiving of tolerance stickups or one side being offset from the other.

## More uses

While we've highlighted one use of these magnets, there are countless other applications where a magnet with pre-applied adhesive might work well. It is a handy solution for crafts, nametags, refrigerator magnets and more!

The video below shows our D81AD-P magnets used in a magnetic box closure.