Magnet shape changes how magnetic flux is distributed, how a part fits into an assembly and how easily it can be manufactured, magnetized and retained. The most common permanent-magnet shapes are discs, rods/cylinders, rings, blocks/bars and arc segments. Pot magnets are a separate magnetic assembly that combines a magnet with a steel cup to concentrate flux toward one working face.
For engineers and procurement teams, shape should be selected from the functional requirement—not from appearance alone. A ring may be ideal for a shaft or rotary sensor, an arc segment for a motor rotor, a block for a linear assembly, and a disc for compact axial holding or sensing.
Common Magnet Shapes at a Glance
| Shape | Typical magnetization | Common applications | Key design consideration |
|---|---|---|---|
| Disc | Usually axial | Holding, sensors, latches, electronics | Diameter-to-thickness ratio affects field and demagnetization margin |
| Rod / cylinder | Axial or diametric | Linear sensors, actuators, fixtures | Long aspect ratio changes field reach and orientation |
| Ring | Axial, diametric, radial or multipole | Rotary sensors, motors, couplings, shafts | OD, ID, wall thickness and pole pattern all matter |
| Block / bar | Through thickness, width or length | Motors, holding, assemblies, separation | Magnetization direction must be called out explicitly |
| Arc segment | Application-specific | Motor and generator rotors | Arc angle, radius, pole orientation and retention are critical |
| Pot magnet assembly | Usually axial working face | Mounting, fixtures, holding | Steel cup improves one-face holding but changes the magnetic circuit |
Disc Magnets
Disc magnets are among the most common stock shapes. They are usually magnetized through the thickness, placing north and south poles on the two flat circular faces.
Discs work well when the design needs a compact circular footprint, simple axial field, easy adhesive bonding, or direct contact with a steel target. Thin discs can have a lower permeance coefficient than thicker parts, so grade, temperature and demagnetization margin should be checked in demanding applications.
Browse neodymium disc and rod magnets or use the Demagnetization & Permeance Coefficient Calculator when geometry is part of the risk assessment.
Rod and Cylinder Magnets
Rod or cylinder magnets can be axially magnetized along their length or diametrically magnetized across the diameter. Axial rods are useful when a longer field profile is needed; diametric cylinders are common in rotary sensing because the field direction rotates with the shaft.
For Hall, AMR or TMR sensing, field magnitude and direction at the actual sensor location matter more than catalog pull force. See Sensor Magnets for Hall, TMR & AMR and the Magnet Field Distance Calculator.
Ring Magnets
Ring magnets are defined by outer diameter, inner diameter and thickness, but the same ring geometry can support very different magnetization patterns. A ring may be axial, diametric, true radial or multipole.
That makes ring magnets useful for shafts, rotary encoders, motor rotors, magnetic couplings and bearing concepts. The drawing should always define both the geometry and magnetization pattern.
See Radial vs. Diametric Magnetization, What Is a True Radial Magnet?, or browse ring magnets.
Block and Bar Magnets
Blocks and bars are well suited to linear assemblies, motor pockets, magnetic fixtures, separators and applications where a rectangular footprint matches the mechanical design.
A block can be magnetized through thickness, width or length. Two blocks with identical dimensions and grade can produce very different usable fields if their magnetization direction differs, so the orientation must be specified on the drawing.
Browse neodymium block and bar magnets or use the Magnet RFQ Builder for a custom geometry.
Arc Segment Magnets
Arc segments are commonly used around cylindrical motor or generator rotors. Important dimensions can include inner radius, outer radius, axial length, arc angle and chamfers, along with the required magnetization direction.
Arc segments may be surface mounted or incorporated into more complex rotor structures. High-speed applications also require careful attention to adhesive systems, sleeves, mechanical retention, temperature and demagnetization margin.
For rotor design context, see Magnets for Electric Motors and How Magnets Work in Electric Motors.
Pot Magnets and Magnetic Mounting Assemblies
A pot magnet is not simply a bare magnet shape. It combines a permanent magnet with a ferromagnetic steel cup or housing that redirects flux toward the working face. This can improve magnet-to-steel holding performance while shielding or reducing field on the opposite side.
Published pull force for a pot magnet still depends on the test setup and should not be treated as a universal safe working load. Steel thickness, air gap, coating, surface condition, shear loading and target geometry all affect real performance.
Browse pot magnets and use the Magnet Pull Force Calculator for engineering estimates.
How Shape Changes Magnetic Performance
- Air-gap field: geometry controls how rapidly field decreases with distance.
- Permeance coefficient: thin or unfavorable geometries can increase irreversible-demagnetization risk.
- Contact area: magnet-to-steel holding depends on both magnetic circuit and usable contact area.
- Magnetization direction: the same physical shape can behave very differently when magnetized on another axis.
- Manufacturability: thin walls, sharp corners, narrow rings and complex arcs may require different grinding, tooling or inspection methods.
- Assembly method: adhesive bond area, press fits, sleeves, fasteners and rotor retention can favor one shape over another.
What to Specify on a Magnet Drawing
- All critical dimensions and tolerances
- Magnet material and grade
- Magnetization direction or pole pattern
- Coating or finish
- Continuous and peak temperature
- Required field, force or torque at a defined working condition
- Inspection method and acceptance criteria
- Annual quantity, packaging and documentation requirements
If you already know the approximate shape, use Search Magnet Inventory. For a custom drawing, unusual geometry or production program, use the Magnet RFQ Builder.
