SmCo block magnets - perpendicular to the surface
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1Read the dimensions and the magnetisation
Blocks are described as length A, width B and height C, so a magnet listed as 20x10x5 is 20 mm long, 10 mm wide and 5 mm high.
The category name tells you the direction: these blocks are magnetised perpendicular to the surface, through the height C. The two large A x B faces are the poles, and that is where the magnet works. The narrow edges do nothing magnetically.
2Choose a block when the footprint matters
A block gives you a defined rectangular pole face, which is what you want when the magnet has to sit in a machined pocket, align with a flat surface or present a straight edge to a sensor.
For point holding or a bore, an SmCo cylinder is the simpler choice. For an assembly with flat faces and tight positioning, the block is easier to reference against.
3Buy for temperature and stability
These blocks are rated in the 201 to 350 °C band, with working temperatures around 300 °C. Their force also changes very little across that range, roughly 0.03 % per degree against roughly 0.11 % per degree for neodymium.
That is the whole argument for SmCo. If your assembly never passes 80 °C, a neodymium block does the same job for a small fraction of the price.
4Use the bare surface to your advantage
SmCo resists corrosion, so the blocks are supplied without any surface treatment. There is no plating thickness on the A, B or C dimension, which makes a milled pocket far easier to size, and there is no coating that can chip in a place you cannot inspect again.
Mill the pocket about 0.1 to 0.2 mm larger than the block and bond it in with an epoxy rated for the working temperature of the assembly.
5Protect the corners
SmCo is the most brittle of the common magnet materials, and a block has sharp corners that chip more easily than the rounded edge of a cylinder. Let blocks meet slowly instead of snapping together, slide them apart sideways rather than pulling them straight off, and keep spacers between loose pieces in storage.
Tip: Match the adhesive to the magnet, not to the room. Fitting a 300 °C block with an epoxy that softens at 120 °C is a common and expensive failure, and when the assembly comes loose the magnet usually gets the blame.
Related categories to the SmCo block magnets category
- SmCo cylinders
- SmCo rings
- SmCo cylinders by diameter
- Heat-resistant magnets
- Neodymium block magnets
- Neodymium blocks by temperature
- Neodymium blocks 151 to 200 °C
- Neodymium 201 to 350 °C
- Ferrite block magnets
- Ferrite 201 to 350 °C
- Neodymium magnet segments
- All samarium magnets
- All magnets
Frequently asked questions about SmCo block magnets
The two large A x B faces. These blocks are magnetised perpendicular to the surface, through the height C, so the poles sit on the largest faces and the narrow edges do nothing magnetically. A block listed as 20x10x5 works through the 20x10 face.
When the geometry has to be flat and referenced. A block gives a defined rectangular pole face that sits in a milled pocket, aligns with a flat surface and presents a straight edge to a sensor. For a bore or simple point holding, an SmCo cylinder is the easier and usually cheaper choice.
They are rated in the 201 to 350 °C band, with working temperatures around 300 °C. Just as important, the force changes by roughly 0.03 % per degree against roughly 0.11 % for neodymium, so the magnet behaves almost the same cold and hot. The exact maximum is listed with each product.
Mill the pocket about 0.1 to 0.2 mm larger than the block and bond it with a two-component epoxy rated for the working temperature of the assembly. Because SmCo is supplied bare, there is no plating thickness to add to the nominal dimensions when you size the pocket. Never press the block into an interference fit.
Yes. SmCo is the most brittle of the common magnet materials, and the sharp corners of a block chip more easily than the rounded edge of a cylinder. Let blocks meet slowly rather than snapping together, slide them apart sideways and store them with spacers between the pieces.
SmCo blocks give you a flat, referenced pole face in a magnet that keeps working at around 300 °C. They are magnetised perpendicular to the large face, rated in the 201 to 350 °C band, and supplied bare, without surface treatment, so there is no plating thickness to add when you size a milled pocket. Their force also shifts far less with temperature than neodymium, which is why they end up in sensors, instruments and hot assemblies rather than in ordinary holding jobs.
