Before you look at any part
- What must the magnet DO — hold, align, latch, click into positions, spring, resist sliding, or release with a twist? The verb decides the pattern.
- How much force, and at what gap? Force at contact and force at 2mm are very different numbers, and a datasheet quotes a specific one.
- What is the mating surface — another magnet, or steel? Magnet-to-steel is usually about half the force of magnet-to-magnet.
The two that catch people out
- How hot will it get, in service and in manufacture? Standard neodymium starts losing strength permanently well below what most people assume, and reflow or powder-coat ovens will do it.
- Is it outdoors, wet or salty? Neodymium corrodes and its plating is a consumable. Ferrite or samarium cobalt may be the right answer even though they are weaker.
Fit and assembly
- How is it held in place — bonded, pressed, or bolted? Countersunk holes change what you can specify.
- Is there anything nearby that a magnetic field would upset? Cards, sensors, screens, pacemakers.
- Does it need to survive being slammed together? Neodymium is brittle and two large magnets meeting at speed will chip each other.
Before you commit to a custom part
- Have you checked a standard part does not already do it? Custom patterns are where cost and lead time live.
- What quantity, and when? The answer changes which supplier is right.
If you can answer those nine, describe the job to us and we will tell you which part fits — including when the honest answer is an ordinary magnet.
Ask us about your specific case