Magnets and screws for 3D prints: sizing the mounting features

Read the magnet datasheet before you model the pocket

Start with the component dimensions. For CSN-10, supermagnete lists a 10 mm pot diameter, 4.5 mm total height, 3 mm bore, a 4.8 mm countersink 0.9 mm deep and a ±0.1 mm tolerance. These describe the magnet, not a ready-to-print pocket. To achieve the intended flushness or fastening method, the design must also define fit and assembly conditions. Do not turn the nominal pot diameter into a universal cavity diameter.

The datasheet identifies a nickel-plated steel pot and lists compatible countersunk screws. It does not say the magnet must be screwed rather than glued, and does not document screw retention in printed plastic; treat fastening choice as a separate design question.

Match the screw to the countersink

The page lists examples of screws whose heads fit CSN-10: DIN 97 in 2.5 mm, ISO 7046-2 M2.5, ISO 14581 M2.5 and ISO 10642 M2. These are standards and nominal diameters; the list does not select screw length, material or supporting part. For a complete order, match the listed head with the intended passage and fastening requirements. Compatibility with the magnet hole does not establish screw retention in plastic.

Check two interfaces separately: screw head against the magnet countersink, then the screw's fastening into its support. The part drawing and screw or fastening-element instructions must address that second question. CSN-10 dimensions supply neither a universal pilot hole in plastic nor a nut or insert reference for every assembly.

Build the fit allowance into the file

The Adafruit magnet bottle holder guide shows a printed strip whose grooves hold the magnets by press fit. The authors note that the slots were designed for 0.4 mm nozzles and that the resulting tolerances may differ from printer to printer. The useful part is the method: they recommend printing a test with a single groove and inserting the magnets before committing to the full strip.

For that project, Adafruit describes a craft knife or file if a magnet will not fit and E6000 if it is too loose. These are not validated CSN-10 fastening instructions. To modify the bottle holder, the guide provides a public Fusion 360 design in several formats: magnet count in the slot sketch, pattern spacing in the timeline and strip length through sketch dimensions. Import into another CAD package is offered without establishing that every format preserves its parametric timeline. Those editable dimensions belong to that file, not a CSN-10 model. For your records, note the file used, changes made and magnet tried, so a coupon result is not assigned to a different reference. Keep the chosen magnet dimensions separate from the fit adjustment rather than silently changing both at once.

What the holding force tells you, and what it does not

supermagnete rates the CSN-10 at roughly 1.3 kg of holding force, about 12.7 N, and roughly 260 g in shear, about 2.55 N. Both numbers come with conditions: maximum force on a smooth, sufficiently thick ferromagnetic counterpart with the full face in direct contact. The sheet states that from a gap of only half a millimeter the pot magnet loses much of its force, and that at a 2 mm gap it no longer holds at all. The manufacturer adds that this gap sensitivity is more pronounced for pot magnets than for plain ferrite or neodymium magnets.

Keep the datasheet's conditions visible: maximum holding force is stated for a smooth, sufficiently thick ferromagnetic counterpart in direct contact. If the design adds a gap or layer between the surfaces, it no longer matches the manufacturer's stated condition. No retention force was measured on a printed part.

Material, orientation and print settings

Adafruit recommends PLA for its own model to reduce warping and says its part can also be printed in ABS, PET or nylon. That list applies to this project. The sources do not compare dimensional stability or press-fit behavior of those materials for a CSN-10 pocket.

Adafruit reports printing on an Ultimaker 2+ with Simplify3D, a 0.8 mm nozzle, 0.96 mm line width and slots facing upward, without supports. Its tolerance paragraph separately says the slots were designed for a 0.4 mm nozzle. Keep those two statements identified rather than combining them into one profile for your printer. Its reported print duration belongs to that older setup; neither time nor fit is guaranteed for your file version. Check the settings and result of your own copy before a batch. A nozzle mentioned in a project is not a specification for the magnet itself.

Check everything before ordering a batch

CSN-10's page lists metal counterparts as accessories, including 10 mm adhesive discs and a 12 mm countersunk disc; these are not magnets. Their presence in the list supplies no holding-force result for your printed assembly. Identify the actual counterpart, its fastening method and any gap created between the faces. Keep an added layer visible in the drawing because it changes the direct-contact condition behind the published value. Record that interface together with the pocket, rather than checking only the magnet diameter.

Before making a batch, record the CSN-10 pot diameter of 10 mm, total height of 4.5 mm, 3 mm bore and 4.8 mm countersink listed on its datasheet, then check the matching screw against your part drawing. The sheet lists several 2 or 2.5 mm screws by standard; do not treat them as interchangeable. Record the test-coupon result and intended mating surface separately: the datasheet states its maximum holding force for a smooth, sufficiently thick surface in direct contact, and says a 0.5 mm gap reduces it substantially. Also check the published 80 °C operating limit. The datasheet also identifies NdFeB material, N38 magnetization, nickel coating and a Q235 steel pot; compare those designations with the part ordered. These figures describe the component, not the holding performance of a printed part.

Sources and limits

• supermagnete — CSN-10, dimensions and force conditions
• Adafruit — Magnet Bottle Holder, project-specific 3D printing guide

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.