Wire Diameter 0.4mm Miniature Ballpoint Pen Refill Compression Spring galvanised

Measure the inner bore of your pen barrel or refill housing with a caliper. The spring OD should be slightly smaller than the bore — typically 0.2mm–0.4mm clearance — so it slides freely without binding. For most standard ballpoint refill housings, the 4mm OD variant is the most common fit; the 4.3mm and 4.5mm variants suit slightly wider housings.

The silver finish is a bright steel surface with no additional coating, making it suitable for dry indoor environments where corrosion is not a concern. The galvanizing finish applies a zinc layer to the steel wire, which slows surface oxidation when the spring is exposed to moisture or humidity. For pen mechanisms used in normal indoor conditions, either finish performs reliably; choose galvanizing if the assembly may encounter condensation or damp storage.

At 0.4mm wire diameter, these are light-duty springs intended for low-load applications such as pen click mechanisms, small button returns, and sensor contacts. The exact spring rate depends on the OD and free length of the specific variant. If your application requires a defined load value in Newtons or grams-force, contact us to confirm suitability before ordering.

Yes. While the product title references ballpoint pen refills as a common use case, the dimensions make these springs suitable for any miniature mechanism that requires a light compression spring — including electronic button assemblies, hobby model suspensions, small valve returns, and precision instrument components. Verify the OD, free length, and wire diameter against your design tolerances before use.

The galvanizing (zinc-coated) variants offer meaningful corrosion resistance for typical indoor and mildly humid environments. The silver (bright steel) variants are not coated and may develop surface oxidation if stored in damp conditions over extended periods. For long-term storage or use in environments with elevated humidity, the galvanizing finish is the recommended choice.

Each variant is sold as a separate line item defined by its WD × OD × Length combination, finish, and packing quantity. To receive multiple sizes, simply add each desired variant to your cart individually. The 10-piece packing option is ideal for sampling several sizes before committing to a larger quantity.

For prototyping or single repairs, the 10- or 20-piece packs keep costs low. For small-batch production or workshop restocking, the 50-piece pack offers a better per-unit value. The 1,000-piece pack is suited for ongoing production runs where consistent supply of a single size is needed. If you require quantities beyond 1,000 pieces, contact us to discuss your requirements.