Shear strength and lateral holding force

We get more questions about shear than any other Polymagnet property. The scenario is always the same: an engineer mounts a conventional magnet on a vertical surface, and it slides. Perpendicular pull feels strong, but lateral resistance is almost nothing. Gravity wins, and the product fails its own spec test.

Single-dipole magnets have never been good at shear. Their field pushes and pulls normal to the surface but offers very little resistance to sideways motion. We’ve spent years solving this. Our Max-Attach product line is the result.

Why conventional magnets slide

A standard neodymium magnet produces a single broad field that extends inches away from the surface. Most of that flux disperses into open air. Thick steel plates capture a portion of it, but thin sheet metal is almost transparent to the field. Flux that passes through the back of the sheet is wasted energy. It contributes zero lateral resistance.

We tested this with off-the-shelf neodymium hooks early in our research. A hook rated at 10 lbs of perpendicular pull held 2-3 lbs at best on a vertical plate. Some held less. The shear-to-tensile ratio for single-dipole magnets is 20-30%, which is abysmal if your application is a vertical mount.

Most product designers know this and compensate. Rubber pads, friction coatings, oversized magnets. None of these fix the magnetic problem. They mask it with friction and mass, and both add cost to the assembly.

How Polymagnets increase lateral holding

Our shear improvement comes from two separate mechanisms.

A Polymagnet’s multi-pole maxel arrangement concentrates flux into tight loops at the magnet face. The field saturates the target metal with less waste because it doesn’t disperse into deep space. A tighter, denser bond between magnet and surface produces more lateral resistance. This is the saturation mechanism: same material, more of the energy contributed to the contact.

The second mechanism is different. Maxels in specific lateral-force codes create shear force components that no single-dipole magnet can generate. The magnetic field itself resists lateral motion, above and beyond the friction that comes from higher perpendicular attachment. Conventional magnets rely on friction alone for their shear resistance. We add a direct magnetic shear force on top of it.

Max-Attach Polymagnets show the combined result. Same size, grade, and material as a conventional magnet, but 2x-8x the shear strength. A conventional dipole that held 3 lbs against lateral force will hold 10-24 lbs as a Max-Attach. We’ve tested this across the full product line, and the results hold at every size. The improvement is consistent whether the target surface is thick steel or thin stamped sheet metal.

Thin metal, where the advantage is largest

Conventional magnets lose shear strength fast on thin targets. We measured a magnet rated for 10 lbs tensile on a thick plate. That same magnet delivered 1-2 lbs of shear on 22-gauge sheet metal. Its field passed straight through the steel without saturating it.

Polymagnets don’t have this problem. The field is concentrated near the surface before it even contacts the target, so thin metal gets saturated from the outset. We’ve confirmed strong lateral holding on substrates thinner than a credit card. A conventional magnet at those thicknesses is decorative at best.

Consumer electronics rely on thin magnetic attachment. Every tablet accessory, phone mount, and laptop connector uses a thin steel plate as its target. A magnet that slides on 24-gauge sheet steel is useless for these products. Our Polymagnets, tuned for that thickness, will hold position under repeated daily use.

SBIR-funded research

Correlated Magnetics received a Phase I SBIR contract with a specific scope. The objectives: quantify the potential of maxel arrays to increase shear force between two magnetic structures, and improve the shear force to displacement curve.

We modeled a wide range of maxel configurations, material grades, and code densities. The project produced a set of design principles for maximizing shear force using permanent magnets alone, no modulated iron, no electromagnets.

One result surprised us. The relationship between maxel density and shear force is not linear. Some code densities create a sudden resistance to lateral movement, a “wall” that gives way all at once when exceeded. Others produce a gradual slope. Both have applications. A quick-release mount needs the abrupt version. Gradual resistance is better for a sliding latch. We can now specify either.

Applications

Polymagnet shear strength serves applications that conventional magnets cannot:

• Wall-mounted displays and fixtures. Full holding force on vertical surfaces without rubber pads or oversized magnets
• Tool holders and industrial hooks. 2x-8x lateral holding improvement for heavy-duty mounting
• Automotive interior trim. Secure attachment to thin stamped steel panels
• Consumer device accessories. Phone mounts, tablet covers, and magnetic cases that stay put under vibration
• Medical device mounting. Sensors and monitors that attach to thin metal equipment rails without sliding

Before Polymagnets, each of these required mechanical fasteners, adhesive, or overbuilt magnet assemblies. The magnet can now carry the lateral load on its own.

Design flexibility

We define shear force specifications in software and manufacture on our MagPrinter. A product designer requests a specific lateral holding force and receives a Polymagnet engineered and tested for that exact number. The shear force curve, onset rate, peak force, and displacement at failure are all adjustable through the maxel code.

Standard shear data is published for every Polymagnet in the catalog. Custom configurations go beyond the published range. We can print and test a prototype within a single working day.

Shear-optimized codes can also be combined with alignment codes on the same magnet surface. The result is a magnet that self-centers during assembly and resists lateral displacement after attachment. Two functions from one piece of magnetic material. We’ve shipped these combined-function Polymagnets into production assemblies. A conventional approach would have needed separate magnets for each function, with a higher part count and cost.

What changes for the designer

Shear used to be the weakness that limited where magnets could go in a product. Vertical mounts, thin-metal assemblies, and anything load-bearing in the lateral direction all required workarounds. More material, more mechanical hardware, more adhesive. Every workaround added weight and assembly time.

Max-Attach and custom shear-optimized Polymagnets remove those limits. A single magnet can hold on a vertical surface, attach to thin sheet metal, and resist vibration-induced drift. The force numbers are published in our catalog, tested under controlled conditions, and reproducible across production volumes.

We encourage engineers to request a sample pair and test them against their current magnets. The difference is obvious the first time you push one sideways on a steel plate.