Introduction
SmCo cylinder magnets are widely used in applications where magnetic stability, high-temperature resistance, and long-term reliability are more important than simply choosing the strongest magnet available. Compared with NdFeB magnets, SmCo magnets usually provide lower maximum magnetic strength, but they offer excellent thermal stability, good corrosion resistance, and reliable performance in demanding environments.
For many custom magnet projects, customers may not need a specific SmCo grade. Instead, they may only require a magnet that meets the size, magnetization direction, and general performance needs of the application. In these cases, choosing the most readily available SmCo grade can help reduce lead time, improve supply flexibility, and simplify quotation.
A typical inquiry may specify:
- Material: SmCo
- Shape: Cylindrical magnet
- Size: 1/4″ diameter × 1″ long
- Magnetization: Axially magnetized
- Quantity: 1000 pcs
- Grade: Not critical; easiest available grade preferred
This guide explains how to select custom SmCo cylinder magnets, how SmCo grades differ, what axial magnetization means, and what information should be provided for accurate quotation and production.
What Are SmCo Cylinder Magnets?
SmCo cylinder magnets are cylindrical permanent magnets made from samarium cobalt magnetic material. They may also be called:
- SmCo cylindrical magnets
- SmCo rod magnets
- Samarium cobalt cylinder magnets
- Axially magnetized SmCo rods
- Custom SmCo round magnets
A cylinder magnet is defined by its diameter and length. When the length is much greater than the diameter, it is often described as a rod magnet rather than a disc magnet.
For example, a magnet with a size of 1/4″ diameter × 1″ long is more accurately described as a SmCo cylinder magnet or SmCo rod magnet, not a thin disc magnet. The aspect ratio affects handling, magnetization, packaging, and application performance.
SmCo cylinder magnets can be manufactured in different sizes, grades, tolerances, and magnetization directions. They are commonly used in sensors, instruments, magnetic couplings, high-temperature assemblies, aerospace components, industrial equipment, and precision positioning systems.
Why Choose SmCo Instead of NdFeB?
NdFeB magnets are often selected when maximum magnetic strength is required in a compact space. However, NdFeB is more sensitive to corrosion and temperature. SmCo magnets are chosen when stability and reliability are more important than the highest possible magnetic output.
| Factor | SmCo Magnets | NdFeB Magnets |
|---|---|---|
| Magnetic strength | High | Very high |
| Temperature stability | Excellent | Grade dependent |
| Corrosion resistance | Better | Usually requires coating |
| Cost | Higher | Lower to medium |
| Brittleness | Brittle | Brittle |
| Best use | High-temperature and harsh environments | Compact high-strength designs |
SmCo magnets are especially valuable when the application involves:
- Elevated operating temperature
- Thermal cycling
- Harsh industrial environments
- Long service life
- Limited access for replacement
- Stable magnetic performance over time
- Better corrosion resistance without heavy coating dependence
For many aerospace, oil and gas, industrial, scientific, and sensor applications, SmCo is selected because it can maintain performance where standard NdFeB may be less reliable.
SmCo5 vs Sm2Co17: Which Grade Should You Choose?
SmCo magnets are mainly divided into two material families:
- SmCo5
- Sm2Co17
Both are samarium cobalt materials, but they differ in magnetic performance, temperature capability, availability, and cost.
SmCo5 Magnets
SmCo5 is the earlier samarium cobalt material family. It generally provides lower magnetic strength than Sm2Co17, but it still offers good temperature stability and corrosion resistance.
SmCo5 may be considered when:
- The application does not require maximum magnetic output
- A moderate magnetic field is acceptable
- The design requires stable performance
- The size and grade are easier to source in SmCo5
- Cost and lead time are important
Sm2Co17 Magnets
Sm2Co17 generally offers higher magnetic performance and better high-temperature capability than SmCo5. It is commonly used in demanding industrial, aerospace, defense, and high-temperature applications.
Sm2Co17 may be preferred when:
- Higher magnetic strength is needed
- The operating temperature is high
- Long-term magnetic stability is critical
- The component works in harsh environments
- The application requires better demagnetization resistance
When the Grade Is Not Critical
In some RFQs, customers say the grade is not critical and ask for the easiest grade to source. This is practical for many custom projects.
If the application does not require a strict magnetic performance target, the supplier can recommend a readily available SmCo grade based on:
- Magnet size
- Magnetization direction
- Required quantity
- Available raw material
- Production schedule
- Cost target
- Application environment
This approach can reduce unnecessary cost and avoid delays caused by over-specifying a grade that is not required.
Axial Magnetization for SmCo Cylinder Magnets
For cylinder magnets, axial magnetization is one of the most common magnetization directions.
In an axially magnetized cylinder magnet, the north and south poles are located on the two circular end faces of the magnet. The magnetic field runs along the length of the cylinder.
N |================| SThis magnetization direction is commonly used for:
- End-face attraction
- Magnetic sensing
- Positioning
- Holding and alignment
- Magnetic couplings
- Plunger-style mechanisms
- Linear magnetic systems
For a magnet specified as 1/4″ diameter × 1″ long, axially magnetized, the magnetization runs along the 1″ length. This should be clearly stated in the quotation request, drawing, and purchase order.
Magnetization direction should never be assumed. A cylinder magnet can also be diametrically magnetized, where the poles are located on opposite sides of the round surface. Axial and diametrical magnetization are not interchangeable.
Size and Tolerance Considerations
A size such as 1/4″ diameter × 1″ long is common in inch-based designs.
Converted to metric dimensions:
| Inch Size | Metric Equivalent |
|---|---|
| 1/4″ diameter | 6.35 mm |
| 1″ length | 25.4 mm |
This is a slender cylindrical magnet rather than a flat disc magnet. The longer shape may provide useful magnetic field distribution along the axis, but it also requires careful handling because SmCo is brittle.
Important dimensional considerations include:
- Diameter tolerance
- Length tolerance
- Roundness
- End-face flatness
- Chamfer or edge condition
- Surface finish
- Whether the drawing controls only dimensions or also material
If the customer provides a drawing only for reference dimensions, the supplier should confirm which specifications are required and which can be treated as reference only.
For quantity production, tolerances should be practical and aligned with the application. Overly tight tolerances can increase cost and lead time without improving function.
Do SmCo Magnets Need Coating?
One advantage of SmCo magnets is that they generally have better corrosion resistance than NdFeB magnets. In many applications, SmCo magnets can be supplied uncoated.
However, coating may still be required depending on the operating environment, handling requirements, and assembly conditions.
Common options include:
| Surface Option | Features | Typical Use |
|---|---|---|
| Uncoated | Common for SmCo, no added coating thickness | High-temperature or internal assemblies |
| Nickel coating | Metallic appearance, added surface protection | General industrial applications |
| Epoxy coating | Better moisture protection | Humid environments |
| Parylene coating | Thin, conformal coating | Precision or sensitive components |
| Gold coating | Specialized surface requirement | Electronic or special applications |
For high-temperature use, coating selection should be reviewed carefully. Some coatings may not be suitable for continuous high-temperature operation, even if the SmCo magnet itself can tolerate the temperature.
If the customer does not specify coating, uncoated SmCo or a practical standard coating may be quoted depending on the application.
Typical Applications of SmCo Cylinder Magnets
SmCo cylinder magnets are used in many industries where compact magnetic components must operate reliably under demanding conditions.
High-Temperature Sensors
SmCo cylinder magnets are widely used in sensor systems where temperature stability is important. They can provide stable magnetic fields for position sensing, speed sensing, and proximity detection.
Aerospace and Defense Components
Aerospace systems often require materials that can withstand temperature variation, vibration, and long service life. SmCo magnets are suitable for such applications because of their stability and resistance to demagnetization.
Oil and Gas Tools
Downhole and drilling environments may involve high temperature, pressure, vibration, and corrosive conditions. SmCo magnets are frequently selected for magnetic couplings, sensors, and measurement tools in these environments.
Scientific Instruments
Scientific and laboratory instruments often require stable magnetic performance and precise dimensions. SmCo cylinder magnets may be used in analytical equipment, measurement systems, and research devices.
Magnetic Couplings
SmCo cylinder magnets can be used in compact magnetic couplings where torque transfer or non-contact motion is required. Their thermal stability makes them suitable for demanding industrial equipment.
Industrial Automation
In automation systems, SmCo magnets may be used for sensors, positioning components, holding mechanisms, and motion control assemblies.
Motors and Actuators
Although NdFeB is common in high-power motors, SmCo may be selected for motors or actuators that operate at elevated temperatures or require long-term stability.
Why “Easiest Grade to Source” Can Be a Good Specification
In custom magnet sourcing, customers sometimes over-specify a magnetic grade without knowing whether that grade is necessary. This can make production more expensive or delay quotation.
When a customer says the grade is not critical, it gives the supplier flexibility to recommend a practical solution.
This can help:
- Reduce lead time
- Improve material availability
- Lower unnecessary cost
- Avoid over-engineering
- Increase production feasibility
- Support faster sample preparation
However, the supplier still needs enough application information to recommend a suitable grade. Even if the exact grade is flexible, the working temperature, magnetization direction, size, and application should be confirmed.
A good RFQ statement may be:
Grade is flexible. Please quote the most readily available SmCo grade suitable for this size and axial magnetization.
This is clearer and more professional than simply saying “any grade.”
Manufacturing Process for Custom SmCo Cylinder Magnets
The production process for SmCo cylinder magnets typically includes several key steps.
1. Material Selection
The supplier selects a suitable SmCo grade based on performance, availability, size, and operating conditions.
2. Pressing and Sintering
SmCo powder is pressed and sintered to create a dense magnetic material with the required properties.
3. Machining
Sintered SmCo is hard and brittle, so machining requires diamond grinding or other controlled processes. For cylinder magnets, diameter and length are carefully processed to meet the required tolerance.
4. Surface Treatment
Depending on the requirement, the magnet may be left uncoated or supplied with a protective coating.
5. Magnetization
For axially magnetized cylinder magnets, the magnet is magnetized through its length so that the poles are on the two circular end faces.
6. Inspection
Inspection may include dimensional measurement, visual inspection, magnetic testing, magnetization direction confirmation, and packaging verification.
7. Packaging
Because SmCo is brittle, proper packaging is important, especially for long slender magnets. Magnets should be separated and protected to avoid chipping during transport.
RFQ Checklist for Custom SmCo Cylinder Magnets
To receive an accurate quote, customers should provide the following information:
| RFQ Item | Example |
|---|---|
| Material | SmCo |
| Shape | Cylinder / rod |
| Size | 1/4″ diameter × 1″ long |
| Grade | Most readily available grade acceptable |
| Magnetization | Axially magnetized |
| Quantity | 1000 pcs |
| Coating | Uncoated or supplier recommendation |
| Tolerance | As drawing or standard tolerance |
| Application | Sensor, coupling, industrial assembly, etc. |
| Temperature | Working temperature if known |
| Drawing | For dimensions only or full specification |
| Documentation | CoA, inspection report, magnetic data if required |
If a drawing is provided only for reference dimensions, this should be clearly stated so the supplier does not quote based on incorrect material or unnecessary drawing notes.
FAQ
What are SmCo cylinder magnets?
SmCo cylinder magnets are cylindrical permanent magnets made from samarium cobalt material. They are used when high-temperature stability and reliability are required.
Is a 1/4″ diameter × 1″ long magnet a disc magnet or cylinder magnet?
It is more accurately called a cylinder magnet or rod magnet because the length is much greater than the diameter.
What is axial magnetization?
Axial magnetization means the magnet is magnetized along its length, with the north and south poles on the two circular end faces.
What is the difference between SmCo5 and Sm2Co17?
SmCo5 generally has lower magnetic performance, while Sm2Co17 usually provides higher strength and better high-temperature capability.
Which SmCo grade is easiest to source?
It depends on size, quantity, and current material availability. If the application does not require a specific grade, the supplier can recommend the most readily available suitable grade.
Do SmCo magnets need coating?
Not always. SmCo has better corrosion resistance than NdFeB and is often supplied uncoated. Coating may still be used for specific environments or surface requirements.
Are SmCo magnets stronger than NdFeB magnets?
No. NdFeB generally provides higher magnetic strength, but SmCo offers better temperature stability and corrosion resistance.
Can SmCo cylinder magnets be customized?
Yes. Diameter, length, grade, tolerance, coating, and magnetization direction can be customized according to application requirements.
What information is needed for quotation?
The most important details are material, size, grade preference, magnetization direction, quantity, tolerance, coating, application, and drawing.
Can samples be supplied before mass production?
Sample availability depends on size, grade, material availability, and production schedule. For custom magnets, samples are often recommended before larger-volume production.
Conclusion
Custom SmCo cylinder magnets are reliable magnetic components for high-temperature, industrial, aerospace, sensor, coupling, and precision applications. Although NdFeB magnets offer higher magnetic strength, SmCo magnets provide excellent thermal stability, better corrosion resistance, and dependable long-term performance in demanding environments.
For specifications such as 1/4″ diameter × 1″ long, axially magnetized SmCo cylinder magnets, the most important quotation details include size, magnetization direction, quantity, tolerance, coating requirement, and whether the grade is fixed or flexible. If the grade is not critical, choosing the most readily available suitable SmCo grade can help reduce lead time and improve sourcing efficiency.
Magnetstek supports custom SmCo cylinder magnets, rod magnets, disc magnets, ring magnets, and magnetic assemblies. Send us your drawing, quantity, working conditions, and grade preference, and our team can help recommend a practical SmCo magnet solution for your application.