AlNiCo Magnets:

Are composed of primarily aluminium, nickel, and cobalt, which were developed in the 1940s. This class of magnet remains a preferred material because of its excellent temperature stability, high magnetic flux density, and corrosion resistance. Alnico magnets are manufactured through a casting or sintering process. The casting process allows for the magnet to be manufactured into intricate and complex shapes, which are not possible with other magnetic materials

Excellent temperature stability, high residual induction and relatively high energy characterise the Alnico materials, which are composed primarily of alloys of Aluminium, Nickel, and Cobalt. They are manufactured through either a casting or sintering process. Cast magnets may be manufactured in complex shapes, such as horseshoes etc. Sintered Alnico offer slightly lower magnetic properties but better mechanical characteristics than cast Alnico.

Cast Alnico 5 is the most commonly used of all the cast Alnico magnets. This material is used extensively in rotating machinery, meters, instruments, sensing devices, and holding applications, to name but a few.
Alnico is hard and brittle and cannot be machined or drilled.  Holes are usually cored in at the foundry, and magnets are cast close to final size and then finished by grinding to close tolerances.

Alnico has a low coercive force and is easily demagnetized if not handled with care.  For optimum performance of Alnico 5, the magnetic length should be approximately 5 times the pole diameter or equivalent diameter.  For example, a 0.250" diameter magnet should be about 1.00" long.
Because of its higher coercivity, Alnico 8 may be used in shorter lengths and disc shapes.