• Sep 09, 2026

SSKC-020 - How to Specify a Custom Magnet: The Complete Engineering Series block

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How to Specify a Custom Magnet: The Complete Engineering Checklist

Document ID: SSKC-020
Series: Engineering Series
Difficulty: Intermediate
Reading Time: 12–15 minutes
Last Updated: September 2026

Why Trust Simple Signman?

Since 1969, Simple Signman has supplied magnetic materials to Canadian manufacturers, printers, distributors, sign professionals, and industrial businesses.

Custom magnet projects often begin with a deceptively simple request:

“We need a stronger magnet.”

But strength alone is rarely enough to define the correct solution.

A reliable custom magnet specification must consider the complete application: material, grade, geometry, magnetization direction, polarity, steel thickness, air gap, load direction, environment, mounting method, tolerances, testing, and quantity.

This guide brings those variables together into one practical engineering checklist.

Introduction

The best way to specify a custom magnet is not to begin with a catalog and ask which magnet looks strongest.

Start with the application.

Define what the magnet must do, where it will operate, what it will attach to, how the load is applied, and what conditions could reduce performance.

A custom magnet should be specified from the application backward—not from the magnet catalog forward.

Once the application is understood, the magnet specification becomes much easier to build.

Contents

Start With the Application

Before specifying material, grade, or dimensions, define what the magnet is supposed to accomplish.

Ask:

  • What is the magnet holding, attaching, detecting, positioning, or moving?
  • Is the application static or dynamic?
  • Is the magnet attaching to steel, another magnet, or a sensor system?
  • What happens if the magnet fails?
  • Is the application safety-critical?
  • Is the magnet replacing an existing part?

This is the most important step because every later specification should support the actual application.

Engineering Insight

The strongest magnet is not necessarily the correct magnet. A technically complete specification balances magnetic performance, geometry, environment, assembly, safety, and cost.

Define the Required Function

The function determines which magnetic characteristics matter most.

Application Function Important Factors
Holding Pull force, steel, air gap, contact area
Vertical mounting Shear force, friction, load direction
Sensor activation Flux density, polarity, working distance
Magnetic coupling Pole pattern, alignment, air gap, torque
Positioning Geometry, field shape, repeatability

Choose the Magnet Material

Different permanent magnet materials offer different combinations of strength, temperature capability, corrosion resistance, cost, and mechanical behaviour.

Common choices include:

  • Neodymium (NdFeB): high magnetic strength and compact size;
  • Ferrite / ceramic: lower cost and good corrosion resistance;
  • Samarium cobalt (SmCo): strong temperature performance and corrosion resistance;
  • Alnico: useful in specialized temperature and sensor applications;
  • Flexible magnetic materials: useful for sheets, strips, signage, and broad-area contact.

Material selection should be based on application requirements rather than strength alone.

Specify the Magnet Grade

For neodymium magnets, grades such as N35, N42, N48, and N52 describe magnetic material properties.

Higher grade can provide more magnetic capability within a similar volume.

However, higher grade does not automatically solve problems caused by:

  • thin steel;
  • large air gaps;
  • poor geometry;
  • incorrect load direction;
  • magnetic saturation;
  • temperature requirements.

For more detail, see SSKC-005 — Neodymium Magnet Grades Explained and SSKC-016 — Magnet Size vs Magnet Grade.

Define Shape and Dimensions

Specify the magnet shape and all critical dimensions.

Common shapes include:

  • disc;
  • cylinder;
  • rod;
  • block;
  • ring;
  • countersunk;
  • arc segment;
  • pot magnet;
  • rubber-coated magnetic assembly;
  • custom shape.

Important dimensions may include:

  • length;
  • width;
  • thickness;
  • diameter;
  • inside diameter;
  • hole size;
  • countersink angle;
  • thread size;
  • mounting features.

Geometry directly affects field distribution and magnetic performance.

See SSKC-017 — Magnet Shape and Aspect Ratio.

Specify Tolerances

Tolerances affect both fit and cost.

Do not specify unnecessarily tight tolerances unless the application requires them.

Possible tolerance requirements include:

  • length;
  • width;
  • thickness;
  • diameter;
  • flatness;
  • parallelism;
  • concentricity;
  • hole position.

Best Practice

Separate critical assembly dimensions from non-critical dimensions. This can reduce manufacturing cost while preserving functional performance.

Define Magnetization Direction

Magnetization direction determines where the magnetic poles are located.

Possible configurations include:

  • axial;
  • diametrical;
  • through thickness;
  • through length;
  • through width;
  • radial;
  • multipole.

Dimensions alone are not enough.

A 40 × 20 × 5 mm block magnet, for example, could be magnetized through the 5 mm thickness, the 20 mm width, or the 40 mm length.

Those versions would behave differently.

See SSKC-018 — Magnetization Direction Explained.

Define Polarity

If polarity matters, identify which reference face should be north and which should be south.

This becomes especially important in:

  • magnet-to-magnet systems;
  • sensors;
  • couplings;
  • multipole assemblies;
  • production assemblies where orientation must be controlled.

Add a reference mark, notch, keyed feature, or drawing callout whenever possible.

See SSKC-019 — Magnet Polarity Explained.

Specify Coating and Surface Protection

Coatings protect magnets from corrosion, wear, and mechanical damage.

Common options include:

  • nickel-copper-nickel;
  • epoxy;
  • zinc;
  • parylene;
  • rubber;
  • plastic coatings.

The correct coating depends on:

  • indoor or outdoor use;
  • humidity;
  • water exposure;
  • salt;
  • chemicals;
  • surface-protection requirements;
  • expected handling.

Define Operating Temperature

Temperature can affect permanent magnet performance.

Specify:

  • normal operating temperature;
  • minimum temperature;
  • maximum continuous temperature;
  • short-term peak temperature;
  • duration of high-temperature exposure.

A high-grade magnet is not necessarily the best option if temperature capability is inadequate.

For more information, see SSKC-009 — Neodymium Magnet Temperature Ratings Explained.

Define the Target Steel

If the magnet attaches to steel, the steel becomes part of the magnetic system.

Specify:

  • steel type;
  • steel thickness;
  • steel dimensions;
  • surface condition;
  • paint or coating;
  • whether the surface is flat or curved.

Thin steel can significantly reduce holding force.

See SSKC-011 — How Steel Thickness Affects Magnet Holding Force.

Measure the Air Gap

An air gap is any non-magnetic separation between the magnet and the target.

It can include:

  • paint;
  • powder coating;
  • adhesive;
  • vinyl;
  • rubber;
  • plastic;
  • protective film;
  • surface irregularities.

Even a small gap can significantly reduce magnetic performance.

See SSKC-012 — The Air Gap Effect.

Define the Required Force

Specify what the magnet actually needs to do mechanically.

Possible requirements include:

  • pull force;
  • holding force;
  • shear resistance;
  • torque;
  • sensor field requirement;
  • coupling force.

Use defined units such as:

  • newtons (N);
  • pounds-force (lbf);
  • kilogram-force (kgf).

Also define the test conditions.

A pull-force value without steel thickness, air gap, orientation, and test method can be misleading.

Define the Load Direction

Load direction can completely change the required magnetic design.

Common load conditions include:

  • direct pull;
  • shear;
  • peel;
  • torque;
  • mixed loading.

A magnet rated for strong direct pull may still slide on a vertical surface if friction is low.

See SSKC-013 — Pull Force vs Shear Force.

Define the Working Distance

Some applications require magnetic performance without direct contact.

Examples include:

  • Hall sensors;
  • reed switches;
  • plastic housings;
  • magnetic couplings;
  • position detection.

Specify the actual working distance.

Performance at 0 mm, 2 mm, 5 mm, or 10 mm can be very different.

Specify Surface Gauss Only When Relevant

Gauss and tesla describe magnetic flux density, not pull force.

If a gauss specification is required, also define:

  • measurement point;
  • distance;
  • probe orientation;
  • temperature;
  • test method.

A statement such as “4,000 gauss” without defined measurement conditions may not be sufficient.

See SSKC-015 — Magnetic Flux Density Explained.

Consider Magnetic Saturation

If the steel path is too thin or too small, the magnetic circuit may become the limiting factor.

In that case, using a stronger or higher-grade magnet may produce only a modest improvement.

This is known as magnetic saturation.

See SSKC-014 — Magnetic Saturation Explained.

Define the Mechanical Mounting Method

The magnet must also be physically integrated into the product.

Possible mounting methods include:

  • adhesive;
  • press fit;
  • countersunk screw;
  • threaded stud;
  • threaded hole;
  • steel cup;
  • plastic housing;
  • overmoulding;
  • mechanical retention.

Mounting method can affect coating, tolerances, air gap, stress, and long-term reliability.

Define the Environment

Environmental conditions may influence magnet material, coating, temperature rating, and assembly design.

Specify exposure to:

  • water;
  • humidity;
  • road salt;
  • chemicals;
  • oil;
  • solvents;
  • UV;
  • dust;
  • vibration;
  • shock;
  • outdoor temperatures.

Define Quantities and Annual Usage

Quantity affects manufacturing method, tooling, MOQ, unit cost, packaging, and lead time.

Specify:

  • prototype quantity;
  • initial order quantity;
  • estimated annual usage;
  • expected order frequency;
  • future production potential.

A supplier may quote a development quantity very differently from a repeat production requirement.

Create a Controlled Supplier Drawing

A custom magnet drawing should include more than dimensions.

Whenever relevant, include:

  • dimensions;
  • tolerances;
  • material;
  • grade;
  • coating;
  • magnetization direction;
  • polarity;
  • pole pattern;
  • reference faces;
  • critical performance values;
  • drawing revision.

Best Practice

Use a controlled drawing revision for all custom magnet projects. Dimensions may remain unchanged while polarity, coating, magnetization, or performance requirements change.

Request Samples and Validate

Custom magnet projects should normally be validated before full production.

Sample evaluation may include:

  • dimensional inspection;
  • fit testing;
  • pull-force testing;
  • gauss measurement;
  • polarity verification;
  • magnetization verification;
  • coating inspection;
  • temperature testing;
  • application testing.

Whenever possible, test the sample in the final assembly rather than only in a laboratory fixture.

Define Incoming Inspection

Before production begins, define what must be inspected when parts arrive.

Possible inspection requirements include:

  • dimensions;
  • polarity;
  • magnetization direction;
  • surface gauss;
  • pull force;
  • coating;
  • appearance;
  • packaging;
  • material certification.

Do not rely on dimensions alone.

An incorrect polarity or magnetization direction may be invisible during normal dimensional inspection.

Define Packaging and Handling

Strong magnets can attract each other through packaging, damage coatings, chip on impact, or create handling hazards.

Packaging requirements may include:

  • individual separators;
  • foam;
  • spacers;
  • polarity-controlled packing;
  • corrosion protection;
  • maximum pieces per box;
  • maximum box weight;
  • special labels;
  • magnetic shielding for transport when required.

Custom Magnet RFQ Checklist

Use the following checklist when preparing a custom magnet request.

CUSTOM MAGNET RFQ CHECKLIST

Application:
Required function:

Magnet material:
Magnet grade:

Shape:
Dimensions:
Tolerance:

Magnetization direction:
North/South reference:
Pole pattern / pole pitch:

Coating:
Operating temperature:

Target steel:
Steel thickness:
Surface coating:

Air gap:

Required pull / holding force:
Load direction:
Working distance:

Mounting method:

Environment:

Prototype quantity:
Initial order quantity:
Estimated annual usage:

Drawing number:
Drawing revision:

Inspection requirements:
Packaging requirements:

This checklist does not mean every project needs every field.

The objective is to identify the variables that matter before a production order is placed.

Custom Magnet Specification Summary

Specification Item Why It Matters
Application Defines the actual problem to solve
Material Controls magnetic properties, temperature capability, corrosion behaviour, and cost
Grade Defines magnetic capability within a given geometry
Dimensions Affect fit, volume, field distribution, and force
Tolerances Affect assembly fit, repeatability, and cost
Magnetization direction Determines pole location
Polarity Controls attraction, repulsion, and assembly orientation
Coating Protects against corrosion and wear
Temperature Helps prevent irreversible magnetic performance loss
Target steel Strongly affects holding performance
Air gap Can dramatically reduce magnetic coupling
Load direction Pull, shear, and peel behave differently
Working distance Defines usable field away from the magnet
Quantity Affects MOQ, tooling, production method, and cost

Common Specification Mistakes

Common Mistake Why It Matters
Asking only for the strongest grade Grade may not be the limiting factor
Providing dimensions without magnetization direction Pole location may be wrong
Ignoring polarity Magnet-to-magnet assemblies may repel or fail
Ignoring steel thickness Holding force may be much lower than expected
Ignoring air gap Paint, adhesive, or plastic may reduce performance significantly
Using pull force as safe working load Real loads may involve shear, peel, shock, or vibration
Approving samples by dimensions only Magnetic function may still be incorrect
Not controlling drawing revision Supplier may quote or produce an outdated specification

Frequently Asked Questions

What information is needed to quote a custom magnet?

At minimum, provide the application, approximate dimensions, required function, operating environment, quantity, and any known performance requirements. A drawing or photo is extremely helpful.

Do I need to know the magnet grade before requesting a quote?

No. If you know the required application performance, dimensions, temperature, and environment, the appropriate grade can often be evaluated from those requirements.

What is more important: magnet grade or size?

Both matter. Geometry, magnetic volume, steel thickness, air gap, and load direction may be equally important or more important than grade.

Why does steel thickness need to be specified?

The steel becomes part of the magnetic circuit. Thin steel may limit the holding force available from the magnet.

Why is air gap important?

Paint, adhesive, plastic, rubber, and other non-magnetic layers increase the separation between the magnet and steel and can significantly reduce performance.

Do I need to specify polarity?

Polarity is especially important in magnet-to-magnet systems, sensors, couplings, and controlled assemblies. For simple attraction to steel, polarity is usually less critical.

What is the difference between polarity and magnetization direction?

Polarity identifies north and south. Magnetization direction describes where those poles are located on the magnet.

Should I specify gauss or pull force?

Use pull or holding force for mechanical holding applications. Use magnetic flux density when a field level at a specific location is required, such as for sensors.

Should custom magnets be sampled before production?

Yes, especially when geometry, polarity, magnetization direction, tolerances, or application performance are critical.

Can Simple Signman help if I do not know all the technical specifications?

Yes. Start by describing the application, the available space, the required function, the environment, and the expected quantities. The remaining magnet specifications can then be evaluated.

Canadian Perspective

Canadian manufacturers often source custom magnets from multiple regions, including Canada, the United States, Europe, and Asia.

Supplier terminology, test methods, polarity conventions, coatings, tolerances, and magnetic specifications may differ.

Canadian applications may also involve:

  • low temperatures;
  • outdoor exposure;
  • road salt;
  • humidity;
  • painted or powder-coated steel;
  • long international supply chains;
  • alternate supplier qualification.

For these reasons, a complete and controlled magnet specification is especially valuable when sourcing custom components.

A replacement part should match not only dimensions and grade, but also magnetization, polarity, coating, performance, and inspection requirements.

Safety Reminder

Custom magnet systems can generate significant attractive or repulsive forces.

High-strength magnets may cause pinch injuries, impact damage, sudden movement, or component failure if improperly specified or installed.

Published pull-force values should not be used directly as safe working loads.

For critical applications, use appropriate engineering safety factors, representative testing, mechanical guidance where required, and secondary retention when failure could cause injury or property damage.

Conclusion

A successful custom magnet specification is much more than a size and grade.

It brings together:

  • application;
  • material;
  • grade;
  • geometry;
  • dimensions;
  • tolerances;
  • magnetization direction;
  • polarity;
  • coating;
  • temperature;
  • target steel;
  • air gap;
  • required force;
  • load direction;
  • working distance;
  • mounting method;
  • environment;
  • quantity;
  • inspection;
  • packaging.

A custom magnet should be specified from the application backward—not from the magnet catalog forward.

The objective is not simply to identify the strongest magnet.

It is to define the magnetic solution that performs reliably, fits the assembly, survives the environment, can be manufactured consistently, and makes commercial sense.

Have a Custom Magnet Application?

You do not need to know every technical specification before contacting Simple Signman.

Tell us what you are trying to accomplish, provide the information you have available, and include drawings or photos when possible.

Our team can help evaluate the remaining magnetic requirements and translate the application into a clearer custom magnet specification.

START YOUR CUSTOM MAGNET APPLICATION →

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You have now completed the second Simple Signman Engineering Series block, covering the most important variables that influence real-world magnet performance and custom magnet specification.

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About Simple Signman

Since 1969, Simple Signman has been Canada's leading source for flexible magnetic materials and neodymium magnets. We help manufacturers, printers, distributors, sign professionals, and industrial businesses find magnetic solutions that perform reliably in real-world applications.

Sharing Magnetic Knowledge Since 1969.

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