Pot magnets are widely used to mount, position, suspend, secure and retrieve components in industrial equipment. Their compact construction can provide high holding force while offering convenient mounting options such as countersunk holes, internal threads, external threads, hooks and threaded studs.
However, choosing a pot magnet based only on its advertised pull force can lead to poor performance in real working conditions. The actual holding capacity depends on the load direction, steel surface, air gap, temperature, vibration, installation method and safety requirements.
This pot magnet selection guide explains the main factors industrial buyers and engineers should consider before choosing a standard product or requesting a custom magnetic holding solution.
What Is a Pot Magnet?
A pot magnet is a magnetic assembly in which a permanent magnet is installed inside a steel cup or shell. Depending on the design, the internal magnet may be made from neodymium, ferrite, samarium cobalt or alnico.
The steel cup performs several important functions:
- It protects the magnet from direct impact.
- It concentrates magnetic flux toward the working surface.
- It provides mechanical mounting features.
- It improves the usable holding force on a suitable steel surface.
- It allows the magnetic assembly to be integrated into equipment.
Unlike a bare magnet, a pot magnet is designed as a functional holding or mounting component. The steel shell becomes part of the magnetic circuit and directs more magnetic flux toward the contact face.
This structure makes pot magnets suitable for industrial fixtures, sensors, signs, lighting equipment, inspection tools, machinery, retail displays and temporary mounting systems.
How Does a Pot Magnet Work?
When the working face of a pot magnet contacts a ferromagnetic surface, such as mild steel, magnetic flux flows from the magnet through the steel cup and into the target material.
A closed magnetic circuit is formed between the pot magnet and the steel surface. Under suitable conditions, this design provides more useful holding force than a bare magnet of a similar size.
The performance of this magnetic circuit depends on several factors:
- Magnet material and grade
- Steel cup design
- Contact area
- Target steel thickness
- Surface flatness
- Air gap
- Load direction
- Working temperature
Pot magnets generally produce their highest holding force when the entire magnetic face contacts a clean, flat and sufficiently thick steel plate.
Any condition that interrupts the magnetic circuit can reduce the actual holding force.
Main Types of Pot Magnets
The mounting structure should match the installation method used in the final application. Choosing the correct structure can simplify installation and reduce the risk of mechanical failure.
Countersunk Pot Magnets
Countersunk pot magnets have a central countersunk hole and can be fixed with a flat-head screw.
They are commonly used for:
- Machine covers
- Interior fixtures
- Display systems
- Access panels
- Industrial mounting plates
- Removable components
When installing this type, the screw should fit the countersunk hole correctly. Excessive tightening force may damage the brittle permanent magnet inside the steel cup.
Pot Magnets With an Internal Thread
Internally threaded pot magnets contain a female thread that can accept a bolt, threaded rod, hook or customized mounting component.
They are suitable for:
- Suspended signs
- Lighting systems
- Sensors
- Temporary fixtures
- Cable management
- Removable equipment
The thread specification, engagement length and load direction should be checked before installation.
Pot Magnets With an External Thread
Externally threaded pot magnets include a threaded stud that allows the magnetic assembly to be secured with a nut or threaded directly into another component.
Common applications include:
- Cameras
- Inspection instruments
- Vehicle accessories
- Work lights
- Monitoring devices
- Positioning equipment
This construction is useful when access to the back of the assembly is available.
Pot Magnets With a Cylindrical Bore
Pot magnets with a straight cylindrical bore can be installed using a bolt or other mechanical fastener.
They provide a simple mounting structure for:
- Machinery
- Fixtures
- Jigs
- Automation equipment
- General industrial mounting
The fastener must not apply excessive pressure directly to the magnet.
Hook and Eyebolt Pot Magnets
Pot magnets can also be supplied with hooks, eyebolts or rings for hanging and temporary suspension.
They may be used for:
- Signs
- Cables
- Tools
- Lights
- Safety barriers
- Temporary displays
The rated pull force should not be treated as the maximum safe hanging load. Load direction and safety factor must also be considered.
Neodymium vs Ferrite Pot Magnets
Neodymium and ferrite are the two most common magnet materials used in pot magnets.
Neodymium Pot Magnets
Neodymium pot magnets offer high magnetic strength in a relatively compact size.
They are commonly selected when:
- Installation space is limited.
- High holding force is required.
- Equipment weight must be minimized.
- A compact magnetic mounting point is needed.
- The application requires a high strength-to-size ratio.
However, neodymium magnets can be sensitive to corrosion and high temperatures. The correct grade, coating and assembly design must be selected according to the operating environment.
Ferrite Pot Magnets
Ferrite pot magnets usually provide lower holding force for the same size but offer good corrosion resistance and stable performance in many general environments.
They may be suitable when:
- Cost is a major consideration.
- A larger magnet is acceptable.
- Moderate holding force is sufficient.
- The application involves outdoor exposure.
- Large production quantities are required.
The best option depends on required holding force, available space, operating temperature, environment and project budget.
Understand the Rated Pull Force
The pull force listed for a pot magnet is normally measured under controlled test conditions. These conditions may include:
- A clean magnetic contact surface
- Direct contact with steel
- A flat and sufficiently thick steel test plate
- A perpendicular pulling direction
- Room temperature
- No vibration or impact
- A gradual and controlled test speed
Real applications are rarely identical to laboratory conditions. Paint, powder coating, rust, oil, curved steel, thin sheet metal and sideways loading can all reduce the available holding force.
For this reason, rated pull force should be used as a reference value—not as a guaranteed safe working load.
Pull Force Is Not the Same as Safe Working Load
A pot magnet advertised with a pull force of 100 kg should not automatically be used to suspend a 100 kg object.
The required magnetic rating must account for:
- Load direction
- Safety factor
- Surface condition
- Dynamic movement
- Vibration
- Impact
- Temperature
- Installation quality
- Consequences of failure
A practical preliminary formula is:
Required rated pull force = actual load × safety factor ÷ estimated application efficiency
For example, suppose a 20 kg component is mounted vertically and the estimated application efficiency is 40%. If the required safety factor is 3:
Required rated pull force = 20 × 3 ÷ 0.4 = 150 kg
This is only an initial calculation. The completed mounting system should still be tested under actual operating conditions.
Consider the Load Direction
Load direction is one of the most important factors in pot magnet selection.
Tensile Load
A tensile or pull-off load acts perpendicular to the steel surface. This is usually the direction used for the manufacturer’s pull force test.
Pot magnets generally perform best under direct tensile loading.
Shear Load
A shear load acts parallel to the steel surface. For example, a magnet attached to a vertical steel wall must resist the downward movement of the mounted object.
Shear holding capacity is usually much lower than perpendicular pull force because the component may slide before the magnet separates from the steel.
Surface friction becomes an important factor in this situation.
Peeling Load
Peeling occurs when one edge of the magnet or mounted component begins to lift away from the steel surface. This creates a localized air gap and can cause the magnetic holding force to decrease rapidly.
Pot magnets should generally be installed so that the load is evenly distributed across the magnetic contact face.
Dynamic Load
Movement, vibration, sudden acceleration and impact can create loads much higher than the static weight of the mounted component.
Applications involving vehicles, machinery, rotating equipment, doors or moving structures require a higher safety factor and physical testing.
Evaluate the Steel Surface
The target steel surface is part of the magnetic circuit. Its material, thickness, shape and surface condition directly affect performance.
Steel Type
Pot magnets work best on ferromagnetic materials such as mild steel.
They do not attach effectively to:
- Aluminum
- Copper
- Brass
- Plastic
- Wood
- Glass
- Most austenitic stainless steels
Some stainless steels may show limited magnetic attraction depending on their alloy composition and manufacturing process. The actual material should be tested instead of assuming that all stainless steel is magnetic.
Steel Thickness
If the target steel is too thin, it may not carry all the available magnetic flux. This can reduce holding force.
Using a larger or stronger magnet does not always solve the problem because the steel surface itself may become the limiting factor.
Surface Flatness
The entire working face should contact the steel as evenly as possible.
Bent steel, weld seams, rough surfaces, raised edges and debris can create gaps and reduce performance.
Surface Cleanliness
Oil, dust, rust, paint and other materials between the magnet and steel can affect both magnetic attraction and friction.
The mounting surface should be clean and stable before installation.
Account for Air Gaps and Coatings
Magnetic holding force can decrease significantly when a non-magnetic gap exists between the pot magnet and the steel surface.
Possible air gaps include:
- Paint
- Powder coating
- Galvanized layers
- Rubber
- Plastic film
- Adhesive
- Dust
- Rust
- Surface roughness
Even a small gap can have a substantial effect, particularly when using compact magnetic assemblies.
If the product will attach to painted equipment or coated steel, the coating thickness and surface characteristics should be included in the selection process.
When Should Rubber-Coated Magnets Be Used?
Standard pot magnets provide direct metal contact, but direct contact may scratch or mark delicate surfaces. A rubber-coated magnetic assembly may be more suitable when surface protection and resistance to sliding are important.
Rubber-coated magnets offer several potential benefits:
- Protection for painted surfaces
- Increased surface friction
- Reduced risk of scratching
- Improved resistance to moisture
- Better grip under shear loading
- Reduced impact against the mounting surface
They are frequently used for mounting cameras, lights, sensors, signs and accessories on vehicles, painted machinery and finished steel structures.
However, the rubber layer also creates a gap between the internal magnets and the target surface. Therefore, the measured pull force may be lower than that of a comparable uncoated pot magnet in direct contact with steel.
The choice depends on whether maximum pull force or surface protection is more important.
Check the Operating Temperature
Permanent magnets do not all perform equally at elevated temperatures.
When selecting a pot magnet, consider:
- Normal operating temperature
- Maximum temporary temperature
- Duration of exposure
- Nearby heat sources
- Cooling conditions
- Temperature cycling
Standard neodymium magnets may not be suitable for high-temperature applications. High-coercivity neodymium grades can provide better temperature resistance, while samarium cobalt or alnico may be considered for more demanding conditions.
The maximum temperature of the entire assembly should be evaluated—not only the theoretical temperature limit of the magnet material. Adhesives, coatings, rubber, plastic parts and surface treatments may have lower temperature limits.
Consider Corrosion and Outdoor Exposure
The steel cup protects part of the magnet, but it does not automatically make the complete assembly waterproof or corrosion-proof.
For outdoor, marine, offshore or humid applications, evaluate:
- Water exposure
- Condensation
- Salt spray
- Chemicals
- Ultraviolet exposure
- Temperature cycling
- Damage to the surface coating
- Crevices where moisture can accumulate
Possible solutions include protective plating, epoxy coating, rubber overmolding, stainless steel components or specially sealed assemblies.
The environmental protection level should be confirmed through application-specific testing.
Choose an Appropriate Safety Factor
A safety factor compensates for differences between controlled test conditions and actual use.
There is no universal safety factor suitable for every magnetic application. The required value depends on the load, environment and consequences of failure.
A higher safety factor may be necessary when:
- The magnet holds an object above people.
- The equipment is exposed to vibration.
- The magnet is mounted on a vehicle.
- The steel surface is painted or uneven.
- The load acts parallel to the surface.
- The application involves shock or movement.
- Failure could damage equipment.
- Surface conditions cannot be controlled.
Magnets should not be used as the only safety device in critical suspended-load applications. A secondary mechanical restraint, such as a cable, bolt, bracket or locking component, may be required.
When Is a Custom Pot Magnet Necessary?
Standard pot magnets are suitable for many general mounting applications. However, a custom magnetic assembly may provide better performance when the project has special dimensional, mechanical or environmental requirements.
Customization may be required for:
- Non-standard dimensions
- Special threads or mounting holes
- Higher operating temperatures
- Corrosive environments
- Curved contact surfaces
- Special pole arrangements
- Integrated handles or brackets
- Specific holding-force requirements
- Restricted installation space
- Rubber or plastic overmolding
- High-volume OEM production
Magnetic simulation and prototype testing can help determine whether a proposed design provides sufficient holding force while controlling size, material use and cost.
Information to Provide When Requesting a Quote
Providing complete application information helps the manufacturer recommend a suitable pot magnet more efficiently.
A useful request should include:
- Application: What will the magnet hold or mount?
- Load: What is the weight of the mounted component?
- Load direction: Is the load perpendicular, parallel or dynamic?
- Target surface: What material will the magnet attach to?
- Steel thickness: How thick is the contact surface?
- Surface condition: Is it painted, coated, curved or rough?
- Operating temperature: What are the normal and maximum temperatures?
- Environment: Will the assembly face water, salt spray, oil or chemicals?
- Mounting method: Is a hole, thread, stud, hook or bracket required?
- Dimensions: What installation space is available?
- Quantity: What are the prototype and annual order quantities?
- Safety requirements: What would happen if the magnetic attachment failed?
Drawings, photographs and application samples are especially helpful for customized projects.
Pot Magnet Selection Checklist
Before choosing a pot magnet, confirm the following:
- Required holding force
- Actual load direction
- Safety factor
- Target steel material
- Steel thickness
- Contact surface flatness
- Paint or coating thickness
- Available installation space
- Required mounting structure
- Operating temperature
- Corrosion exposure
- Vibration and impact
- Surface protection requirements
- Need for a secondary mechanical restraint
- Prototype testing requirements
A pot magnet should be selected as part of the complete mounting system rather than as an isolated component.
Choosing the right pot magnet requires more than comparing diameter and advertised pull force. Reliable performance depends on the magnetic circuit, target steel, load direction, contact condition, operating temperature, environment and installation method.
Neodymium pot magnets are suitable for compact applications that require high holding force, while ferrite pot magnets can provide a cost-effective solution for moderate holding requirements. Rubber-coated magnetic assemblies are often preferred when painted surfaces need protection or additional friction is required.
For demanding industrial applications, the safest approach is to calculate the preliminary holding requirement, apply an appropriate safety factor and test the complete assembly under real working conditions.
WZ Magnetics provides standard and custom pot magnets for industrial holding, mounting and positioning applications. Contact our team with your load, dimensions, working surface and environmental requirements to evaluate a suitable magnetic solution.
Need Help Selecting a Pot Magnet?
Send us your application details, required holding force, dimensions and working conditions. Our team can help evaluate a standard or custom magnetic solution.
Frequently Asked Questions
What is the difference between a pot magnet and a regular magnet?
A pot magnet places a permanent magnet inside a steel cup. The steel cup protects the magnet, concentrates magnetic flux toward the working face and provides practical mounting features. A regular bare magnet does not usually offer the same mechanical protection or installation options.
How strong should my pot magnet be?
The required strength depends on the object weight, load direction, steel surface, air gap, vibration and safety factor. The magnet’s rated pull force should be higher than the actual load because real working conditions are usually less favorable than laboratory test conditions.
Why is the actual holding force lower than the rated pull force?
Rated pull force is generally measured on a clean, flat and sufficiently thick steel plate under perpendicular loading. Thin steel, paint, rust, surface roughness, air gaps, shear loading and vibration can reduce actual performance.
Can pot magnets hold objects on a vertical wall?
Yes, but a vertical installation creates a shear load. The object may slide even if the magnet has a high perpendicular pull-force rating. Surface friction, object weight and vibration must be evaluated.
Do pot magnets work on stainless steel?
It depends on the stainless steel grade. Many austenitic stainless steels provide little magnetic attraction, while some ferritic and martensitic grades are magnetic. The actual steel should be tested before final selection.
Which is better: a neodymium or ferrite pot magnet?
Neodymium pot magnets generally provide higher holding force in a smaller size. Ferrite pot magnets are often more economical and offer good corrosion resistance. The correct material depends on space, required force, temperature, environment and budget.
Can pot magnets be used outdoors?
They can be used outdoors if the magnet, steel cup, coating and assembly structure are designed for the environment. Water, salt spray, temperature cycling and coating damage must be considered.
Are rubber-coated magnets stronger than standard pot magnets?
Rubber-coated magnets may provide better friction and resist sliding, but their rubber layer creates a magnetic gap. Their direct pull force may therefore be lower than that of a comparable metal-faced pot magnet.
Can the advertised pull force be used as the safe working load?
No. Advertised pull force is a reference test value and should not automatically be treated as the safe working load. An appropriate safety factor and actual application testing are required.
Can WZ Magnetics produce custom pot magnets?
Yes. Pot magnets can be customized according to dimensions, magnet material, mounting structure, thread, coating, temperature, corrosion protection, holding force and production quantity.
