Surface Finish / Coating:

Standard finish is Ni–Cu–Ni (nickel), with optional coatings such as zinc, black/color epoxy, gold (Ni–Cu–Ni–Au), silver (Ni–Cu–Ni–Ag), chrome, parylene, or phosphating; the choice affects corrosion resistance, wear, and appearance, so pick nickel for general use, epoxy for extra corrosion protection, and noble finishes when aesthetics or additional barrier layers are required.

Tolerance:

Typical manufacturing tolerance for a 40×20 mm disc is about ±0.05–0.10 mm on diameter and thickness for ground parts; commodity listings can be looser (±0.10–0.20 mm or ~±1%), while tighter control such as ±0.02–0.05 mm is available on request with additional grinding, cost, and lead time.

Magnetization Direction:

The most common is axial magnetization through the thickness, placing the north and south poles on the two flat faces; diametrical magnetization is less common for solid discs, and multi-pole patterns usually apply to rings or specialized applications, so specify axial unless your fixture explicitly requires another orientation.

Pull Force / Holding Force:

Holding force depends heavily on the test setup—steel grade and thickness, air gap, surface finish, and whether the load is tensile or shear—so published values vary; as a rough benchmark, a thinner N52 block of similar face area (40×20×5 mm) can show ~15 kg pull under ideal conditions, and a 20 mm-thick disc will be substantially higher (often in the tens of kilograms) when tested against thick, low-carbon steel with near-zero gap—always request the supplier’s method and fixture details.

Max Operating Temperature:

For N52 (“N” series) the recommended maximum operating temperature is ~80 °C; higher-temperature grades (M ≈100 °C, H ≈120 °C, SH ≈150 °C, UH ≈180 °C, EH ≈200 °C, AH ≈220 °C) increase heat tolerance at the cost of some peak magnetic performance, so select the temperature rating according to your application’s thermal profile.