{"product_id":"small-compression-springs-ballpoint-pen-spring-0-4mm-wire-dia","title":"Small Compression Springs Ballpoint Pen Spring 0.4mm Wire Dia 18 20 25 30mm Long","description":"\u003cdiv class=\"hdiy-desc\"\u003e\n\u003cdiv class=\"hdiy-overview\"\u003e\n\u003ch2\u003eSmall Compression Springs for Ballpoint Pens — Precise Force in a Miniature Form\u003c\/h2\u003e\n\u003cp\u003eWhen a ballpoint pen skips, a clicker mechanism fails, or a precision instrument loses its tactile feedback, the culprit is almost always a worn or incorrectly sized compression spring. Engineers, repair technicians, and DIY enthusiasts who work with fine-tolerance assemblies need a reliable source of miniature compression springs that deliver consistent load performance across repeated cycles.\u003c\/p\u003e\n\u003cp\u003eThese small compression springs feature a 0.4mm wire diameter and outer diameters ranging from 4mm to 4.5mm (approximately 0.157–0.177 in), with free lengths of 18mm, 20mm, 25mm, and 30mm (approximately 0.71–1.18 in). Available in spring steel (natural finish) and zinc-coated steel for added corrosion resistance, each spring is wound to close tolerances suitable for compact mechanical assemblies.\u003c\/p\u003e\n\u003cp\u003eTypical applications include ballpoint pen click mechanisms, retractable marker assemblies, small electronic push-button switches, miniature valve return springs, and precision instrument reset mechanisms — anywhere a compact, reliable compression spring for small devices is required.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"hdiy-compat\"\u003e\n\u003cspan class=\"hdiy-compat-icon\"\u003e🔧\u003c\/span\u003e \u003cstrong\u003eCompatibility:\u003c\/strong\u003e Designed for standard ballpoint pen barrels, retractable writing instruments, and compact mechanical assemblies requiring OD 4–4.5mm compression springs with 0.4mm wire diameter.\u003c\/div\u003e\n\u003ch2\u003e✅ Key Features of These Small Compression Springs\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-features\"\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e📏\u003c\/div\u003e\n\u003cstrong\u003eMiniature Dimensions\u003c\/strong\u003e\n\u003cp\u003eWire diameter 0.4mm, OD 4–4.5mm, free length 18–30mm — engineered for tight-clearance pen mechanisms and compact devices where space is critical.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e⚙️\u003c\/div\u003e\n\u003cstrong\u003eTwo Material Options\u003c\/strong\u003e\n\u003cp\u003eSpring steel offers excellent elasticity and fatigue resistance for dry indoor applications; zinc-coated steel adds a protective layer for environments with light moisture exposure.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🔄\u003c\/div\u003e\n\u003cstrong\u003eConsistent Cycle Performance\u003c\/strong\u003e\n\u003cp\u003eClose-wound coil geometry maintains stable spring rate across thousands of compression cycles, reducing the risk of set or premature fatigue in high-use mechanisms.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e📦\u003c\/div\u003e\n\u003cstrong\u003eFlexible Pack Quantities\u003c\/strong\u003e\n\u003cp\u003eAvailable in 10, 20, 50, and 1000-piece packs — suitable for single repairs, prototyping runs, and small-batch production alike.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🎯\u003c\/div\u003e\n\u003cstrong\u003eMultiple Length Options\u003c\/strong\u003e\n\u003cp\u003eChoose from 18mm, 20mm, 25mm, and 30mm free lengths to match your specific assembly stack height and required deflection range.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003cdiv\u003e\n\u003cdiv class=\"hdiy-icon\"\u003e🛡️\u003c\/div\u003e\n\u003cstrong\u003eZinc-Coated Variant Available\u003c\/strong\u003e\n\u003cp\u003eThe zinc-coated option provides corrosion inhibition for applications exposed to humidity or light chemical contact, extending service life in demanding environments.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/div\u003e\n\u003ch2\u003e📐 Technical Specifications — Miniature Compression Springs\u003c\/h2\u003e\n\u003cdiv class=\"hdiy-table-wrap\"\u003e\n\u003ctable\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003cth\u003eSpring Type\u003c\/th\u003e\n\u003ctd\u003eCompression Spring\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eWire Diameter\u003c\/th\u003e\n\u003ctd\u003e0.4 mm (0.016 in)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eOuter Diameter (OD)\u003c\/th\u003e\n\u003ctd\u003e4 mm – 4.5 mm (0.157 – 0.177 in)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eFree Length\u003c\/th\u003e\n\u003ctd\u003e18 mm, 20 mm, 25 mm, 30 mm (0.71 – 1.18 in)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eMaterial\u003c\/th\u003e\n\u003ctd\u003eSpring Steel \/ Zinc-Coated Steel (see variant options)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eFinish\u003c\/th\u003e\n\u003ctd\u003eNatural (Spring Steel) \/ Zinc Coating (Zinc-coated)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eCoil Direction\u003c\/th\u003e\n\u003ctd\u003eRight-hand wound\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eEnd Type\u003c\/th\u003e\n\u003ctd\u003eClosed ends\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eSpring Rate\u003c\/th\u003e\n\u003ctd\u003eSee variant options\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003ePack Quantity\u003c\/th\u003e\n\u003ctd\u003e10 pcs \/ 20 pcs \/ 50 pcs \/ 1000 pcs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003cth\u003eApplication\u003c\/th\u003e\n\u003ctd\u003eBallpoint pens, retractable instruments, precision devices\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"hdiy-faq\"\u003e\n\u003ch2\u003e❓ Frequently Asked Questions\u003c\/h2\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow do I choose the right length for my ballpoint pen spring?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eMeasure the free (uncompressed) length of your existing spring or the available cavity depth in your pen barrel. Add approximately 20–30% to the compressed working length to determine the required free length. For most standard ballpoint pens, the 18mm or 20mm options are the most common fit.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is the difference between spring steel and zinc-coated variants?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eSpring steel springs are made from uncoated high-carbon steel wire, offering excellent elasticity and fatigue life in dry indoor environments. Zinc-coated springs have an additional zinc layer that provides corrosion inhibition, making them more suitable for applications with occasional humidity or light chemical exposure.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eAre these springs strong enough for repeated clicking in a pen mechanism?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eYes. The close-wound coil geometry and spring steel material are selected for fatigue resistance under repeated compression cycles. These springs are designed to maintain consistent return force across thousands of actuations typical of click-pen mechanisms.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan I use these springs in applications other than ballpoint pens?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eAbsolutely. The 0.4mm wire diameter and 4–4.5mm OD make these springs suitable for miniature push-button switches, small valve return mechanisms, precision instrument reset assemblies, retractable markers, and any compact device requiring a light-load compression spring in this size range.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWill the zinc-coated springs rust if used outdoors or in humid conditions?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eZinc coating provides a meaningful level of corrosion resistance for light moisture and humidity exposure. However, for prolonged outdoor use or direct water contact, additional sealing or a stainless steel alternative would be more appropriate. These springs are best suited for indoor or semi-protected environments.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow do I confirm the OD fits my assembly bore?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eThe outer diameter of the spring should be slightly smaller than the bore or housing it sits in, typically with 0.1–0.3mm clearance. For a 4mm OD spring, a bore of 4.1–4.3mm is recommended. Check the variant options for the exact OD of each size before ordering.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat pack size should I order for a repair vs. production use?\u003c\/summary\u003e\n\u003cdiv class=\"hdiy-faq-body\"\u003e\n\u003cp\u003eFor single repairs or prototyping, the 10-piece or 20-piece packs provide enough springs to test fit and have spares. For small-batch production or workshop stock, the 50-piece pack offers a cost-effective balance. The 1000-piece pack is intended for production runs or resellers requiring bulk quantities.\u003c\/p\u003e\n\u003c\/div\u003e\n\u003c\/details\u003e\n\u003c\/div\u003e\n\u003cdiv class=\"hdiy-cta\"\u003e🛒 Select your wire diameter, OD, length, and quantity above, then add to cart.\u003c\/div\u003e\n\u003c\/div\u003e\n\u003cp\u003e \u003c\/p\u003e","brand":"HomeDIYer","offers":[{"title":"0.4*4*20 (10pcs) \/ Spring steel","offer_id":52449875263762,"sku":"GLFBWJJDLWJ00057x1","price":2.72,"currency_code":"USD","in_stock":true},{"title":"0.4*4*20(10pcs) \/ Zinc-coated","offer_id":52449875296530,"sku":"GLFBWJJDLWJ00058x1","price":2.82,"currency_code":"USD","in_stock":true},{"title":"0.4*4*25 (10pcs) \/ Spring steel","offer_id":52449875329298,"sku":"GLFBWJJDLWJ00059x1","price":2.75,"currency_code":"USD","in_stock":true},{"title":"0.4*4*25(10pcs) \/ Zinc-coated","offer_id":52449875362066,"sku":"GLFBWJJDLWJ00060x1","price":2.84,"currency_code":"USD","in_stock":true},{"title":"0.4*4*30 (10pcs) 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