If you’ve ever tested a small neodymium disc on a steel plate, you know it can be tricky — it slides, it chips, or the holding force feels much weaker than the magnet’s rated pull force.
That’s where pot magnets (also called cup magnets, rubber steel magnets, or mounting magnets) come in.
As a China-based rare earth magnet supplier, we often get this question from overseas buyers:
“Why would I use a pot magnet instead of a bare N52 block?”
Let’s break it down with real-world holding force data, mechanical protection, and cost logic.
1. What Exactly Is a Pot Magnet?
A pot magnet is a permanent magnet (usually ferrite or neodymium) encased in a steel pot or cup. The steel cup concentrates the magnetic flux onto one face, while shielding the other sides.
This design creates a “magnetic circuit” that:
- Maximizes holding force on ferromagnetic surfaces (steel, iron)
- Minimizes stray magnetic fields (safer for nearby electronics)
- Protects the magnet from impact and corrosion
Common shapes: round, rectangular, with or without a mounting hole (threaded or countersunk).
2. Holding Force Comparison: Pot Magnet vs. Bare Neodymium
Let’s take a D25x7mm neodymium pot magnet vs. a bare N45 disc magnet of similar volume.
| Magnet Type | Pull Force on 10mm Steel Plate | Best for | Risk |
|---|---|---|---|
| Bare N45 Disc (25x7mm) | ~25 kg (rated) | Air gap / through-hole | Chipping, sliding, corrosion |
| Neodymium Pot Magnet (D25x7mm) | 38–45 kg (actual) | Steel surface mounting | None (steel cup protects) |
Why does the pot magnet hold more?
The steel cup redirects the magnetic field from the back and sides toward the contact face. On a bare magnet, much of the flux is wasted on the back side.
In plain language:
A pot magnet of the same size often holds 1.5–2x stronger on a clean steel surface than a bare magnet with the same grade and volume.
3. When Should You Choose Pot Magnets? (Real Industrial Cases)
We see pot magnets used in three main scenarios by global buyers:
✅ 1. Mounting & Fixturing (Most Common)
- Holding sensors, signs, LED lights, or tooling on metal machinery
- Quick-release assembly without drilling holes
✅ 2. Lifting & Holding (Light to Medium Duty)
- Magnetic sweepers, lifting magnets for steel plates
- Holding dies or molds in presses
✅ 3. Welding & Positioning
- Ground clamps for welding (threaded pot magnet)
- Temporary holding of steel parts for alignment
Pro tip for buyers: If your application involves sliding or shear force (not just vertical pull), choose a pot magnet with a rubber face — it increases friction dramatically.
4. Coating & Corrosion Resistance: Why Steel Cup Matters
Bare neodymium magnets are extremely prone to rust — even Ni-Cu-Ni coating can fail after scratches.
A pot magnet’s steel cup acts as a physical barrier. For harsh environments (outdoor, marine, chemical), we offer:
| Coating Type | Protection Level | Typical Use |
|---|---|---|
| Zinc-plated steel cup | Basic | Indoor, dry conditions |
| Epoxy-coated cup | High | Outdoor, humidity |
| Stainless steel cup (304/316) | Very high | Marine, food processing |
Many European buyers now request 304 stainless steel pot magnets for food-contact or wash-down areas.
5. Cost Consideration: Pot Magnet vs. Custom Assembly
If you need a threaded mounting hole or a rubber outer layer, you can either:
- Buy a standard pot magnet (lowest cost, ready to ship)
- Encapsulate a bare magnet in a custom steel housing (higher cost, longer lead time)
For 80% of industrial mounting applications, a standard off-the-shelf pot magnet from a China supplier is the most cost-effective solution — often 50–70% cheaper than custom-molded assemblies.
6. How to Specify Pot Magnets for Your RFQ
When you email a Chinese supplier (like us), include these parameters for a fast & accurate quote:
- Magnetic material: Neodymium (strongest) or Ferrite (cheapest, corrosion-resistant)
- Outer diameter & height (e.g., D32x10mm)
- Hole type: Countersunk / threaded blind hole / through-hole with stud
- Steel cup material: Mild steel / stainless steel 304 / stainless steel 316
- Holding force requirement (in kg or lb)
- Operating temperature (standard ≤80°C, high-temp SH/ UH grades available)
Sample spec: “D40x11mm neodymium pot magnet, countersunk hole, N35 grade, 80kg pull force, zinc-plated cup, max temp 80°C.”
Summary Table: Pot Magnet vs. Bare Magnet Decision Guide
| Factor | Pot Magnet | Bare Neodymium Magnet |
|---|---|---|
| Holding force on steel | ✅ Higher (flux focused) | ❌ Lower (flux wasted on back) |
| Protection against chipping | ✅ Fully enclosed | ❌ Very fragile |
| Corrosion resistance | ✅ Steel cup + coating | ❌ Coating only |
| Mounting flexibility | ✅ Threaded hole / countersink | ❌ Requires gluing or housing |
| Cost per holding force | ✅ Very efficient | ❌ More expensive to mount safely |
Final Recommendation for Global Buyers
If you are mounting magnets directly onto a steel surface — for fixtures, signs, sensors, jigs, or light lifting — choose a pot magnet.
If you need a magnet to work through an air gap (e.g., inside a plastic housing, or attracting from a distance), choose a bare neodymium magnet.
Need Pot Magnets for Your Next Project?
We are a direct manufacturer of sintered neodymium magnets based in China, supplying pot magnets, mounting magnets, and custom magnetic assemblies to buyers in Europe, North America, and Southeast Asia.
✅ No minimum order quantity for standard sizes
✅ Fast 15–25 day production
✅ Full material certs (NdFeB grade, coating test, pull force test)
✅ Free technical drawing support
👉 Contact us for a pot magnet sample or send your RFQ to: sales@nbtechmagnet.com