Grinding and Tolerances
Alnico is hard and brittle (45-55 Rockwell C), and is not suitable for drilling, tapping or conventional machining operations. Holes are usually rough cast during the foundry process and magnets are cast close to their final size and then finish machined to closer tolerances if necessary. Adams provides in-house cutting and grinding to meet your application requirements.
The most efficient utilization of Alnico magnets requires that they be magnetized after the magnet is assembled in the final magnetic circuit. Shipping the alnico magnets before magnetizing them also eliminates the need for special packaging and prevents contamination by potential contact with ferrous materials.
Learn more about magnetization of alnico magnets
Temperature Constraints and Demagnetization
Alnico has the best temperature coefficient of any but the most advanced commercial magnet material, providing for excellent stability over a wide temperature range. A properly designed circuit using Alnico magnets will have a stable flux output during temperature fluctuations.
Learn more about temperature constraints and demagnetization of alnico magnets
Other Design Considerations
Because Alnico is hard and brittle and not suitable for drilling, tapping or conventional machining operations, it is not usually used as a structural component in product design. We recommend selecting simple shapes when possible, fitting into slots rather than holes. Cross sections of less than .125" (3.18 mm) should be avoided. Finishing increases cost, so if your application can use “as cast” or “as sintered” then cost will be lower.
For holding applications requiring mounting, or to protect the magnet, alnico assemblies such as rotors or magnetron magnets may be supplied with aluminum housings. Alnico may be painted for aesthetic reasons, like the ever popular red horseshoe magnet.
Alnico Magnet Manufacturing Methods
Most alnico magnets are manufactured using typical foundry casting techniques, where the molten alloy is poured into sand molds. Very small magnets, usually one ounce or less, are produced using press and sinter techniques. Sintered Alnico magnets have features which make them particularly effective in very small precision devices. Sintering magnets with small holes and intricate shapes is possible. Sintered magnets are available in both isotropic and anisotropic form, with a broad range of unit properties. Their magnetic properties are similar but often slightly lower than cast magnets of equivalent grade.
Alnico magnets, cast and sintered, are finished ground using abrasive grinding to produce the final shape and tolerance. Once ground the material is a shiny metallic finish. These materials are brittle and cannot be machined or drilled.
Alnico cast and sintered in our Elmhurst, IL facility is ISO9001:2008 certified, and DFARS and ITAR compliant.