Magnet Dimensional Tolerances
Magnets are readily available in Blocks, Discs, Cylinders & Rings. JOFOV Magnetics specializes in the supply of short-run prototype magnets including Arc Segments, various magnetic orientations etc. If you need a magnet size, submit a Design-a-Magnet enquiry for a quote on your custom magnet design.
As a purchasing manager, your facility and products must meet specific requirements. One such requirement is reliable tools and components — in this case, magnets. Whether you need to hang something from the ceiling or sew a magnetic clasp into a shirt, any magnet you use must fall into a permissible range of dimensions (depending on the shape, grade, and material).
Any variation that falls outside the dimensional tolerance (for example, if it’s too big or too small) is noncompliant. The purpose of knowing this range — the formal dimensions of a completed magnet — is to specify leeway for variations in manufacturing.
Just as a ½-inch by 2-inch neodymium disc magnet may be better for one application than a ½-inch by 3-inch neodymium disc magnet, a ½-inch by 2-inch magnet may be preferable to a ½-inch by 2.004-inch magnet. Many businesses cannot tolerate even such a minor variance.
Dimensional Tolerances at JOFOV Magnets
In general, the magnets available at SDM Magnets have fairly standard machine tolerances — +/- 0.003 inches to +/- 0.005 inches. The variation can exist in both diameter and width, so be sure to take that into consideration if exact measurements are required for your purposes. To give you a better idea of what we mean:
A ¼-inch by ¼-inch cylinder magnet has a tolerance of +/- 0.003 inches.
A 3-inch by 3-inch cylinder magnet has a tolerance of +/- 0.005 inches.
The standard NdFeB magnet tolerance is +/-0.1mm. It is possible to produce most shapes to +/-0.05m tolerances but the magnet may cost more.
For tighter tolerances we would have to review the shape to inform you of the tolerances we could achieve (most applications +/-0.05mm is the best). The shape and finish determines the tolerances that can be achieved.
Factors to Consider For Dimensional Tolerances
As you increase the size of a magnet, its coating may become thicker. Some large neodymium magnets have as many as three protective layers — a base layer of nickel, a middle layer of copper, and a final layer of nickel. This extra protection is crucial for durability; however, each layer can have a thickness of roughly 0.032 inches. If you are unable to verify all measurements before purchasing, or are unsure, our team is always on standby to help answer any tolerance questions. Call us or fill out the form on our contact page.
Also, note that every layer of coating creates a small amount of separation between the magnet and the ferromagnetic material surrounding it. Though the space is small, it is enough to decrease overall magnetic strength.
At JOFOV , our stock magnets are ideal for most applications, and we perform routine inspections to ensure only the best products are shipped out. When an order comes in, we hand inspect a randomly selected sample to check for tolerance. If there are too many problematic magnets, we ship them back to the manufacturer. If our regular stock magnets don’t meet your tolerance levels, we can also deliver customized magnets that meet your specific requirements, even down to +/- 0.001 inches. Visit our custom magnets request form for more information.