How to Choose a Pot Magnet for Your Application
If you’re looking for a magnet with extremely strong single-sided attraction, easy installation, and durability, consider Pot Magnet. Here’s what you actually need to know to choose the right pot magnet.
1. What Is a Pot Magnet?
A pot magnet (also called a cup magnet or mounting magnet) is a permanent magnet – typically a sintered neodymium disc – assembled inside a low-carbon steel cup. The steel housing forms a closed magnetic circuit that concentrates virtually all magnetic flux onto one working face. This makes a pot magnet deliver significantly higher practical holding force per unit volume than a bare magnet of the same dimensions.
The term “pot magnet” reflects the shape: the steel cup resembles an inverted pot, with the magnet seated at the base and the open face directed toward the ferromagnetic target surface.
Pot magnets ship with various integrated mounting structures – countersunk holes, internal female threads, external male studs, through holes, or swivel hooks – so they can be fastened directly into mechanical assemblies, jigs, fixtures, or equipment without additional brackets or adhesive.
2. How Does a Pot Magnet Work?
When a bare neodymium disc magnet attracts to a steel surface, its magnetic flux radiates in all directions. Much of that flux is “wasted” in the air rather than concentrated at the contact interface.
The steel cup in a pot magnet changes this completely. Low-carbon steel has high magnetic permeability and acts as a flux guide. The cup walls and base channel the flux so it exits almost entirely from the open bottom face. The result is a tightly focused, high-density flux zone at the working surface.
Key effect: Compared to a bare magnet with the same size and grade, the closed magnetic circuit can multiply practical holding force by a factor of 3× to 6×. The steel shell also physically protects the brittle neodymium core from impact, chipping, and cracking during handling and installation.
What a pot magnet requires to achieve rated pull force:
- Direct, full-face contact with a thick, clean, flat, low-carbon steel surface
- No air gap between the magnet face and the target
- Load applied axially (perpendicular to the working face)
- Any deviation from these ideal conditions reduces measured holding force.
3. Types of Pot Magnets
Selecting the correct mounting configuration ensures optimal load transfer and streamlined assembly. Below are the five primary industrial pot magnet types. If you would like to learn more, please click on the names of the pot magnets to access further information.
Table 1: Pot Magnet Types Comparison
| Pot Magnet Type | Mounting Method | Primary Advantage | Key Limitation | Typical Application |
| Countersunk Hole | Flat-head countersunk screw | Flush surface mounting | Screw head must sit completely flush | Door stops, cabinet latches, signs |
| Internal Female Thread | Mating male threaded bolt/stud | Modular, adjustable connection | Requires external male hardware | Industrial lighting, sensor brackets |
| External Male Stud | Through-hole with nut/washer | Direct panel mounting without bolts | Fixed stud length | Cable tray suspension, HVAC mounts |
| Through Hole | Socket head cap screw/hex bolt | Heavy-duty industrial clamping | Bolt head protrudes above surface | Welding jigs, heavy equipment bases |
| Flat (No Hole) | Direct magnetic adhesion – no fasteners, no drilling | Maximum flux utilization | Load capacity drops sharply under shear or vibration | Temporary outdoor signage, LED ceiling light installation |
4. How to Choose the Right Pot Magnet?
When specifying a pot magnet for an engineering application, follow this systematic step-by-step selection framework:
Step 1: Application: Identify whether the pot magnet holds a fixed load, provides a closeable latch, serves as a removable fixture, or supports a hanging tool. Each application has a different load profile, duty cycle, and failure consequence.
Step 2: Holding Force: Calculate or estimate the working load. This is the actual force that must be resisted — not the catalog pull force. Apply a safety factor of at least 2×.
Step 3: Load Direction: Pot magnets are optimized for axial pull force (perpendicular to the working face). If used in the direction of shear force (anti-slip), the required sliding breaking force is typically 15% – 30% of the vertical pull force. If your load has a significant shear component, select a larger magnet or consider using a rubber or silicone coating to increase friction and prevent slipping.
Step 4: Mounting Method: Use the comparison table above to select the mounting type that matches your installation method, access constraints, and serviceability requirements.
Step 5: Magnet Size: Determine maximum allowable outer diameter (OD) and thickness based on operating conditions.
Step 6: Coating: NiCuNi (nickel-copper-nickel) is standard for dry indoor environments. Epoxy coating is preferred for wet, chemical, or outdoor service. Rubber coating provides surface protection and a non-scratch contact face.
Step 7: Operating Temperature: Standard N-grade NdFeB has a maximum operating temperature of 80 °C (N50/N52: 60–70 °C). Above this limit, irreversible demagnetization begins. Note that magnetic output also drops reversibly at roughly 0.1% per °C as temperature rises from room level. Verify the maximum working temperature of your application and match to magnet grade.
Step 8: Safety Factor: After selecting the candidate pot magnet, divide its rated pull force by your chosen safety factor. The result must exceed the actual working load. If it does not, increase the diameter, upgrade the grade, or use multiple magnets.
(1) Formula 1: Calculate of Safe Vertical Pull Force for Pot Magnets
If your pot magnet is directly subjected to vertical pull force, the evaluation should meet the following requirements:
Fallowable, vertical = Frated, vertical / SF > Factual, vertical
· Fallowable, vertical= Safe Allowable Vertical Force
· Frated, vertical= Rated Breakaway Pull Force
· SF = Safety Factor
· Factual, vertical= Actual Vertical Working Load
(2) Formula 1: Calculate of Shear Force & Friction Load for Pot Magnets
If your pot magnet is attached to a vertical wall and is subject to downward sliding forces, the coefficient of friction should be considered into the evaluation, and meet the following requirements:
Fallowable, shear = (Frated, vertical × μ) / SF > Factual, shear
·Fallowable, shear = Safe Allowable Shear Force
· Frated, vertical= Friction Force
· μ= Coefficient of Friction
· SF = Safety Factor
·Factual, shear= Actual Shear Working Load
5. FAQs
Q1: Can pot magnets withstand outdoor or high-humidity environments?
A1: Not the standard ones. The NiCuNi coating is made for dry, indoor use – outdoors, moisture creeps into the gap between the steel cup and the magnet core, rusts it from the inside, and the magnet weakens. For wet or humid jobs, choose epoxy-coated, rubberized, or stainless steel cup versions instead.
Q2: Will tightening the installation screw too much break the pot magnet?
A2: Yes, it can. The magnet core inside is hard but brittle – over-tightening, especially on countersunk or through-hole types, can crack it. Stick to the recommended torque and keep the screw head flat against the magnet.
Q3: Why is my pot magnet slipping down the wall?
A3: Because the rated pull force is measured straight off a steel plate, not down a wall. On a vertical surface, the load becomes sliding force, and bare steel doesn’t grip well — most pot magnets start sliding at just 15–30% of their rated pull. Fix: go up a size, add a bigger safety factor, or use a rubber-coated magnet for extra grip.
Q4: Why does my pot magnet feel weaker on thin or painted metal?
A4: Holding force decreases on thin metal because the steel target saturates magnetically and cannot conduct the full flux. Paint, rust, or surface plating creates a non-magnetic air gap, which reduces magnetic force.
Q5: Are pot magnets demagnetized over time, and what is their expected lifespan?
A5: Practically no. Sintered neodymium loses less than 1% of its strength per 100 years – as long as it isn’t cracked, overheated, or hit by strong opposing magnets. The real enemy is rust: keep the housing and coating intact, and the magnet will outlast your application.
Contact Us
XF Magnet build custom neodymium pot magnets from 10 mm to 120 mm diameter, with pull forces up to 600 kg, in five mounting configurations — countersunk, through hole, internal thread, male stud, and hook — plus flat and rectangular designs. Need a thread from M3 to M12 machined in, a non-standard OD or pull force, or a coating for wet or outdoor service? Just send us the numbers.
Send us your drawing, or simply list:
- Working load, and how it is applied — axial pull, or shear/sliding
- Outer diameter, height, and thread size required
- Environment: dry indoor, wet, chemical, or outdoor
- Target annual quantity
Email your requirements to info@xf-magnet.com — every inquiry is answered, not a canned price list.