What Neodymium Magnet (Holder) for Water Searches?

The mandatory equipment is a magnet with a holder (preferably UMP 75x25 [M10x3] GW F200 GOLD with Rope set price ~ 200 PLN). Without it, you won't go far ;)

Optional equipment includes:

• Protective gloves. To avoid injury from sharp objects - they are included in the set,
• Bucket / box / bag. So you have somewhere to put the retrieved items and take them home or to a collection container. Leaving a large amount of scrap on the shore doesn't look good. Responsible treasure hunters leave not only a clean river but also a clean shore,
• Cloth for wiping hands and the magnet holder. This will extend the lifespan of the magnetic holder,
• Steel hook. Heavier finds such as bicycles, motorcycles, or benches cannot be retrieved using a magnet alone - use a hook for the rope,
• And if you have a hook, you'll need an additional rope to attach it.

What is the difference in magnetic force when it acts perpendicularly to the surface compared to the lateral shearing force?
This depends on the surface to which you attach the magnet, the thickness of the metal, iron, or steel base, and also how you use the magnet.
Whether the magnet only holds paper on a magnetic board or it is a magnetic hook attached to the side of the refrigerator, where a bag of legumes is also hanging.
The force of the magnet, when loaded parallel to the surface of the substrate, is only 15-25% of the magnet force we mentioned. The magnet will attract ferromagnetic materials in the direction of the magnetic field.

If you attach a magnet to a vertical surface, such as a steel plate on a wall or a refrigerator door or a metal cabinet, the magnetic force will be weaker. However, this also depends on other factors. In the case of placing the magnet on a vertical surface, the shearing force also comes into play. It increases or decreases depending on the friction between the magnet and the supporting vertical base. If you attach a shiny, nickel-plated magnet to a polished surface, it will not stick to it as well as if the magnet had an anti-slip surface, such as a rubber coating. Because the layer of rubber on the rubber-coated magnet is slightly thicker than the nickel-plating layer itself, the magnet is further away from the supporting base, and the holding force also changes slightly.

equal lifting force (floor and ceiling)

the surface must be flat for a greater force

the surface must be thick for the magnet to have something to grip onto

We test the magnetic force of magnets on a polished steel plate made of S235JR material with a minimum thickness of 10 mm, which is considered the best among commonly available steel grades. This way, we test the force of all magnets, except for load-bearing magnets, where we use thicker materials.

How can we better illustrate the difference between holding force and shearing force?

Attach a neodymium magnet to a refrigerator door.
a) Take the magnet in your hand and pull it away from the surface of the refrigerator towards yourself.
b) Reattach the magnet to the refrigerator. This time, simply move the magnet up or down the refrigerator door.

When did the magnet become easier to move?
As you can see, it's option b) because when sliding on smooth refrigerator doors, coated magnets do not hold as strongly. However, if a thin anti-slip foil were attached to the refrigerator, moving the magnet would be much more difficult. This also applies to other cases, not just with magnets. Sliding a full cardboard box on a smooth floor is much easier than on a shaggy-type carpet because the friction is much greater.

The actual lifting capacity for magnetic holders (120 kg, 290 kg, 330 kg, 480 kg, etc.) indicates the breaking force for each magnet. It represents the maximum weight of items that the magnet can still hold.

The numbers may seem high, but they are measured under ideal conditions. During magnet fishing, finds are often rusty and only touch a small portion of the magnet. Underwater, there are also roots, rocks, and other obstacles that can cause the detachment of the find from the magnet. That's why the magnet needs to have a much greater force than the weight of the objects being pulled.