highly holding force magnetic pot

Specifications

These magnets have a countersunk central hole on the front (magnetic) face of the magnet.

A pack of 1 - 20mm dia x 7mm thick x 4mm c/sink N42 Neodymium Pot Magnet. The NORTH pole is on the centre of the front face and the SOUTH is on the outer edge around it (both poles are on the same face). These Magnets are plated with 3 layers of protective coatings - Nickel + Copper + Nickel (Ni-Cu-Ni).

Each magnet can support a steel weight of up to 7.5kg vertically from the magnetic face when in flush contact with a mild steel surface of equal thickness to the magnet. Each magnet can also support up to 1.5kgs in a shear position before beginning to slide down a steel surface under the same conditions. These magnets can be fixed in place using a 4mm c/s Screw and have a maximum operating temperature of 80 degrees C  

What is pot magnets?

Pot magnets are made up of magnets (NdFeB, SmCo, AlNiCo or Hard Ferrite) and other spare parts, such as metal, plastic, rubber and other components. Sometimes Pot magnets can meet some special requirements while a single magnet can not do. In the meantime, using pot magnets can save more cost than just using magnets and gain the same purpose.

How to choose a pot magnet?

The basic principle of the holding or pot magnet is to direct and concentrate the flux from both magnetic poles to one active face. This is usually achieved with steel pole pieces or a steel-backing cup.
The standard selection can be broken down into three material types and there is a great variety of systems available. The following data should act as a simple guide:

1) Sintered Ferrite, this material offers a good performance from an inexpensive magnet, however, they tend to be bulky and are not always suitable where space is an important factor. The steel parts are plated & the Ferrite is inert thus corrosion is limited. Maximum operating temperature is +120 degree Celsius.

2) Cast AlNiCo, offers a better holding force than Ferrite systems and is the only pot magnet that can be heated to extreme temperatures. However, the high cost of the Cobalt content in the cast magnet makes the price prohibitive unless the application requires temperatures over +120 degree Celsius up to a maximum of +500 degree Celsius .

3) Rare Earth Samarium & Neodymium, pots and assemblies can offer up to eleven times the performance of a Ferrite system in a comparable size. Applications tend to be specialized engineering projects where performance and available space are key factors. Maximum operating temperatures are +60 degree Celsius C for the Neodymium and +150 degree Celsius  - +250 degree Celsius C for the Samarium depending on the design configuration.

When considering your selection, please be aware of the following factors: The stated Kg Pull (holding/gripping force) is based on the magnets retaining force against a direct pull when offered to a clean ground mild steel surface with a minimum thickness of 6mm. Painted or un-ground surfaces will reduce this force, assemblies working in shear will support approximately 1/3 of the stated value.