Neodymium SemiCircle Magnets

Half the circle, with more ways to fit. Neodymium Semi-Circle Magnets combine the magnetic strength of NdFeB with a practical flat edge for positioning, pairing, and space-saving designs. Ideal for assemblies where a full round magnet simply won't work.

Send Inquiry

Neodymium Semi-Circle Magnet Design and Features

A neodymium semi-circle magnet starts as one of our disc blanks, cut in half and ground square on the diameter edge. It is sintered NdFeB, nickel-copper-nickel plated, and magnetized through the thickness.

The straight edge is the reason for the shape. It provides a flat datum for locating, a shoulder that allows two halves to close into a full disc, and a clear visual line for marking the pole axis. A plain disc offers none of these features.

Standard Sizes and NdFeB Grades

Sizes are defined by full diameter plus thickness, cut from the same blanks as our standard discs. Four sizes are kept in stock. The table below lists them with the weight of one half and of the matched pair.

Standard grade is N42. N45 is available when the same footprint needs higher holding force.

semicircle sizes table

Applications of Neodymium Semi-Circle Magnets

Most units ship as matched halves, because the pairing is the point. Two halves form a simple mechanical clutch: one fixed, one free to rotate. The operator adjusts holding force by turning it - no electronics, no wiring. It is one of the lowest-cost adjustable holding solutions available.

In sensor arrays and Halbach-style stacks, the half shape is used where a full disc would cover the sensing area. Dial bases and chucks use the flat side as a reliable datum. A half-round pocket simply accepts a semi-circle where a full disc will not fit.

Dimensional Tolerances, Magnetization and Coatings

Diameter and thickness are held to approximately ±0.1 mm. The straight edge is ground square to the curve so that two halves close without a step.
Axial magnetization (poles on the two flat faces) is standard. For sensor work we can magnetize with the reference on the diameter edge instead - this is easier to set before grinding than after.
Nickel plating is the default. Epoxy over nickel is recommended for damp environments or parts that are handled frequently.

Storage and Handling of Semi-Circle Magnets

Store the halves closed together rather than apart. Kept this way, they retain their pull force for as long as the rest of the shop inventory.

Ordering

When the design calls for a neodymium semi-circle magnet instead of a full disc, send the diameter, thickness, and the function of the flat edge. Grade and magnetizing direction will be confirmed with the quotation. Sizes outside the standard table are cut and ground to drawing.

FAQ

Q: Why choose a semi-circle magnet instead of cutting a standard disc yourself?

A: Cutting sintered NdFeB requires specialized equipment because the material is hard and brittle. Improper cutting can cause chipping, coating damage, and dimensional inaccuracies. Factory-cut semi-circle magnets provide cleaner edges and more consistent results.

Q: Will two semi-circle magnets have the same holding force as one complete disc magnet?

A: Not necessarily. Even when two halves form a complete circle, their combined holding force depends on magnetization direction, alignment, gaps, and the contact surface. A matched pair can approach the performance of a full disc under suitable conditions, but the actual force should be verified in the assembly.

Q: Does the straight edge affect how a semi-circle magnet should be installed?

A: Yes. The straight edge can serve as a positioning reference against a flat surface or within a half-round pocket. For paired assemblies, accurate edge alignment helps minimize gaps and maintain consistent positioning.

Hot Tags: neodymium semicircle magnets, China neodymium semicircle magnets manufacturers, suppliers, factory, block shape neodymium magnet, Bonded Neodymium Magnet, brushless dc motor magnet, Parylene Coated Magnet, Permanent Magnet Brushless Motor Magnet, trouble free permanent magnet