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Countersunk Discs
Screw-Mount Rare Earth Discs
Countersunk Neodymium Disc Magnets (Screw-Mount)
CMS Magnetics stocks precision-machined sintered neodymium countersunk disc magnets (NdFeB), featuring a central 90° beveled hole designed for standard flat-head screws. Available in grades from N35 through ultra-high-energy N52, these screw-mount discs provide strong, non-slip mechanical fastening onto non-magnetic surfaces such as wood, aluminum, drywall, and 3D prints without requiring messy liquid adhesives. Finished with an industrial triple-layer Ni-Cu-Ni electrolytic coating for corrosion defense and wear resistance.
Looking for heavy impact protection, plain discs, or alternative shapes? For repetitive metal-on-metal slamming, choose steel-encased Neodymium Cup Magnets to prevent brittle edge chipping. For press-fit or adhesive installations, view our Neodymium Disc Magnets, or return to our master Neodymium Magnets catalog to explore rectangular blocks and rings.
Flush Mechanical Mount
Precision 90° chamfer seats flat-head screws flush with the magnetic face to eliminate air gaps.
North, South & Pairs
Choose North-facing or South-facing bevels, or order matched pairs for magnet-to-magnet attraction.
High-Strength Grades
Available in N35 to N52 with triple-layer Ni-Cu-Ni plating for standard indoor corrosion resistance.
Standard Hardware Sizing
Hole diameters accommodate standard fasteners (#4, #6, #8, #10, M3, M4, M5).
Engineering Guide: Countersunk Neodymium Disc Magnets
Countersunk rare earth disc magnets provide a permanent, non-adhesive mounting solution where structural adhesives or double-sided tapes cannot withstand heavy shear loads, cyclic vibration, or environmental exposure. By recessing a screw head directly inside the magnet’s profile, these discs achieve flush contact with attracting surfaces for maximum pull force.
Understanding Countersunk Polarity: North vs. South & Matched Pairs
Because sintered neodymium is axially magnetized (poles run through the thickness), the face containing the wider countersunk opening has a specific magnetic pole:
- Attracting to Steel / Ferrous Metal: You can use either North or South poles. A flat steel plate, bracket, or screw strike attracts both poles with equal holding strength.
- Attracting Magnet-to-Magnet: You must purchase a Matched Pair (one North-countersunk and one South-countersunk). If two identical magnets with the same polarity are screwed down facing each other, they will repel.
Hardware Compatibility & Installation Best Practices
| Magnet Outer Diameter | Hole Specification | Recommended Fastener | Mounting Caution |
|---|---|---|---|
| 3/8" to 1/2" | 90° Chamfer / ~0.12" Thru | #4 Flat-Head Screw (M3) | Do not overtighten. Hand-tighten only. |
| 5/8" to 3/4" | 90° Chamfer / ~0.15" Thru | #6 Flat-Head Screw (M3.5) | Set drill clutches to low torque. |
| 7/8" to 1-1/4" | 90° Chamfer / ~0.20" Thru | #8 or #10 Flat-Head Screw (M4/M5) | Ensure flat seating to prevent point stress. |
Notice: Sintered neodymium is a brittle ceramic-like material. Over-torquing screws or using high-torque impact drivers can snap or chip the magnet around the countersunk bore.
Frequently Asked Questions
Should I use stainless steel or standard carbon steel screws?
Non-magnetic stainless steel screws (such as 304 or 316 grade) are recommended to ensure the magnetic flux projects outward rather than shunting through the fastener head. If you use zinc-plated carbon steel screws, a small portion of flux is diverted into the screw head.
How do I order magnets for a magnetic door or cabinet latch?
For a door latch where the magnet makes contact with another magnet on the door frame, order our Matched Pairs (equal quantities of North and South). If your door frame has a simple zinc or steel strike plate, any single countersunk disc magnet will hold securely.
What is the maximum operating temperature for countersunk magnets?
Standard grades (N35–N52) operate reliably up to 80°C (176°F). For high-heat environments such as machinery or lighting enclosures, CMS Magnetics also manufactures high-temperature grades: M (100°C), H (120°C), and SH (150°C).
What is the difference between a bare countersunk disc and a cup/pot magnet?
Bare countersunk discs are thinner, lighter, and expose both magnetic poles. A round neodymium cup magnet encloses the disc inside a nickel-plated steel cup, shielding the brittle NdFeB alloy from repeated direct slamming impacts while redirecting flux forward to dramatically multiply holding power on flat steel surfaces.