Arc and segment magnets are curved pieces, and motor applications are the context in which buyers most often ask about them, because a curved magnet can follow a curved surface in a way a flat block cannot. This guide explains the arc geometry published on this site, why motor use does not add a specification of its own, and what a motor-related arc inquiry should contain. It names no motor, no motor model and no motor performance figure, because none is published for arcs on the company's pages.
The arc geometry: three customized figures
An arc or segment is defined by its outer diameter, its inner diameter and its angle, and all three are listed as customized for this shape. There is no published arc size table to quote, and that absence is informative: it means the buyer supplies the geometry rather than selecting from a list. The tolerance line is still published — standard ±0.05 mm and minimum ±0.02 mm — and the listed magnetization directions are diametrical, through thickness and through circumference. A complete arc inquiry therefore contains the three curved figures, the tolerance required, the grade series under discussion, and the direction copied exactly as listed.
The angle deserves emphasis, because it is the figure buyers most often omit. An arc with the right diameters but the wrong angle is the wrong part, and an angle given in the wrong unit or without a reference for where it is measured from will need a clarifying question. Send the angle with its unit and, where possible, a sketch showing how it is measured, so the review can confirm the geometry without reconstructing it. The same applies to the inner and outer diameters: state both, because an arc inquiry with only one diameter is geometrically incomplete.
Why motor context does not change the specification
Motor use is an application context, not a specification. It does not add a size, a grade or a direction to the arc range, and it does not license borrowing a figure from another shape's table. A motor inquiry that says arc magnets for motors, without diameters, angle, grade series and direction, will be answered with questions, because the context alone does not determine the part. Conversely, a complete arc specification — three figures, tolerance, grade series, direction, operating temperature — can be reviewed whether the end use is a motor or anything else, because the review checks the part, not the context label.
Operating temperature matters in motor contexts because motors generate heat, and the grade discussion should therefore use the temperature the magnet will actually see, not the ambient temperature. Discuss the series against the shared table, from 80°C for N35–N52 to 200°C for 28EH–38EH, and state the temperature explicitly rather than assuming a series from a grade name. If the temperature is unknown, say so and ask what information is needed to discuss it, rather than letting a grade be chosen by default.
No arc photograph, and why that is stated plainly
This site publishes no product photograph for arc and segment magnets, and the arc detail page says so in a notice rather than substituting a photograph of another shape. The reason is a matter of record on the image list: the company's arc image file, when opened, proved to be a load-failed placeholder rather than a photograph of an arc magnet, and it was excluded rather than published. A buyer who needs a visual reference for an arc should therefore rely on the dimensioned sketch in the inquiry, not on a photograph, and should not accept a photograph of a disc or block as evidence of an arc's appearance. That restraint is part of the same evidence discipline that governs every figure on this site.
The absence of a photograph does not affect the specification: diameters, angle, tolerance and direction are all published in text, and text is what the review checks. But it does affect how an inquiry should be written. Without a photograph to point at, the sketch and the three figures carry the whole geometry, and they should be given with the care that a photograph would otherwise seem to provide. A sketch with labelled diameters, angle and direction is worth more than a paragraph describing a curve.
Questions to send with an arc magnet inquiry
A specification that can be answered names four items together: the shape family, dimensions inside that family's published range, the grade temperature series, and the magnetization direction exactly as listed for that shape. Add the operating temperature and the fixing method where they affect the choice, and ask coating and warranty as open questions. Please confirm minimum order quantity and lead time before ordering. Warranty terms are unavailable on the published pages — please confirm warranty terms before ordering. Certificates are available upon request; no certificate number or issuing body is published here.
An inquiry that names only a grade, or only a size, will be answered with questions rather than a confirmation, because neither item alone is a complete specification. The extra sentence that states the direction in plain words, or that gives the mating dimension for a fixing, is often the sentence that prevents a second round of correspondence, and it costs nothing to include at the start.
Frequently asked questions
Which grade series should I discuss for arc magnets for motors?
Discuss the grade series against the shared grade maximum working temperature table, using the temperature the magnet will actually see in service, including heat from neighbouring parts. The series run from N35–N52 at 80°C through the M series at 100°C, the H series at 120°C, the SH series at 150°C and the UH series at 180°C to the EH series at 200°C. State the operating temperature as a figure in the inquiry, because a grade name without its temperature row has not been specified for a warm environment, and the review needs the temperature to confirm the series discussion rather than infer it from a name alone.
How exactly should I state the magnetization direction?
Copy the direction exactly as listed for the shape named in the inquiry, and do not substitute a synonym that feels equivalent, because the same word can describe a different arrangement on a different shape. Where a drawing uses a different convention, add a plain-words description of the pole positions alongside the listed term, so the review can reconcile the two without guessing. A direction that is assumed rather than confirmed is a common source of a magnet that is dimensionally correct and magnetically wrong for its fixing, so the extra sentence describing the poles is worth writing even in a short inquiry.
What should I ask about coating, warranty and certificates?
Please confirm coating requirements before ordering, because coating type names were not transcribed from the company illustration and no coating type is named on this site; state the operating environment with the coating question so the answer can be specific. Warranty terms are unavailable on the published pages, so please confirm warranty terms before ordering rather than assuming a term. Certificates are available upon request: name the certificate required and its purpose in the inquiry, because no certificate number, issuing body, scope or validity period is published here, and a named request can be matched to the order it belongs to.
What if my size or combination is not in the published range?
Ask whether it can be made, and send the dimension as written rather than rounding it into the published range. A value outside a shape range, a direction not listed for that shape, or a combination of features from two shapes should be raised as an explicit question, with a dimensioned sketch where the geometry is curved, holed or otherwise not captured by a single size figure. Please confirm minimum order quantity and lead time before ordering. A question asked before ordering costs one message; a forced fit into the nearest published table can cost the whole part, because a magnet that matches its order and fails its fixing is worse than an extra round of questions.