--- title: "What Are Linch Pins (Spring-Leg Retaining Pins) Used For?" description: "Linch Pins (Spring-Leg Retaining Pins) (Trade series (linch pin)) are used for connections made and broken by hand many times, where a threaded fastener woul…" url: https://engineeringhardware.com/applications/linch-pins/ source: Engineering Hardware & Fasteners --- # What Are Linch Pins (Spring-Leg Retaining Pins) Used For? Pins · Trade series (linch pin) · Application guide Typical applications, the industries that specify linch pins (spring-leg retaining pins), and how to choose the right size, material and finish for the joint. Linch Pins (Spring-Leg Retaining Pins) are used for connections made and broken by hand many times, where a threaded fastener would be far too slow. They are manufactured to Trade series (linch pin), and selection is driven by the nominal diameter, the fit and tolerance the assembly requires, and the service environment. - **Primary duty:** Connections made and broken by hand many times, where a threaded fastener would be far too slow - **Governing standard:** Trade series (linch pin) - **Nominal diameter range:** 6 mm to 12 mm - **Category:** Pins Application notes are general engineering guidance. Verify the property class and any approval requirement against your own design calculation. ![What Are Linch Pins (Spring-Leg Retaining Pins) Used For? application image](https://engineeringhardware.com/wp-content/uploads/2026/08/Linch-Pins.webp) Linch Pins (Spring-Leg Retaining Pins) are selected when an assembly calls for connections made and broken by hand many times, where a threaded fastener would be far too slow. This application guide to the Trade series (linch pin) type covers concrete end-uses, the specification checklist, correct installation, and where an alternative fastener performs better. Stocked across roughly 6 mm to 12 mm, they cover general to heavy-duty work. ## Typical Applications for Linch Pins (Spring-Leg Retaining Pins) The most common settings where these are specified: - **Linkages & hinges:** pivot points carrying light shear. - **Machine alignment:** dowelling mating housings so they reassemble in the same position. - **General machine building:** fastening covers, brackets, motors and sub-assemblies on production equipment. - **Maintenance & repair (MRO):** a stocked size for servicing existing plant where the original fastener spec must be matched. - **Fabrication & metalwork:** bench and on-site assembly of steel frames, enclosures and weldments. 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This product spans 6 mm–12 mm; check the full table below for the exact dimensions of each size. - **Material:** Choose the material and finish for the service environment — plated steel for general use, stainless for corrosion resistance. - **Environment:** For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient. - **Standard:** This product is supplied to Trade series (linch pin). Quoting the standard on your order guarantees interchangeable dimensions between suppliers. ## Installation & Assembly Practice - Ream the hole to the specified fit class; a dowel pressed into a drilled-only hole will not locate accurately. - Press pins in with steady force rather than hammer blows where possible, and chamfer the hole entry. ## Common Selection Mistakes with Linch Pins (Spring-Leg Retaining Pins) - Using a dowel pin as a load-carrying shear bolt — dowels locate, they are not sized for sustained shear. - Ignoring the fit class: a locational fit and an interference fit need different hole tolerances. ## Where Linch Pins (Spring-Leg Retaining Pins) Are Not the Right Choice Not for carrying significant tensile or repeated heavy shear loads — use a bolt or a keyed joint for that. Custom manufacturing · Made to drawing ## Need a linch pins (spring-leg retaining pins) outside the standard range? Tolerance class is what a special pin usually turns on — a locating pin and a retaining pin want very different fits in the same nominal size. Made by cold heading or turning. Minimum order from 2,000 pieces; samples within 7 days of drawing approval. [Custom pin manufacturing](https://engineeringhardware.com/custom/pins/)[Send a drawing](https://engineeringhardware.com/custom/pins/#rfq) ## Technical Drawing Dimensioned line drawing of 6 Linch Pins (Spring-Leg Retaining Pins) to Trade series (linch pin). Side view and top view, drawn to the dimensions in the table below and redrawn for any size selected. - **Usable length (mm):** 32 - **Ring diameter (mm):** 25 - **Spring leg:** Integral wire - **Working load (kg):** 200 - **Material:** Spring steel - **Finish:** Zinc plated - **Retainer:** Integral ## Dimensions & Specifications (Trade series (linch pin)) | Shank diameter d (mm) | Usable length (mm) | Ring diameter (mm) | Spring leg | Working load (kg) | Material | Finish | Retainer | | --- | --- | --- | --- | --- | --- | --- | --- | | 6 | 32 | 25 | Integral wire | 200 | Spring steel | Zinc plated | Integral | | 8 | 42 | 30 | Integral wire | 350 | Spring steel | Zinc plated | Integral | | 10 | 50 | 35 | Integral wire | 550 | Spring steel | Zinc plated | Integral | | 12 | 60 | 40 | Integral wire | 800 | Spring steel | Zinc plated | Integral | Inside the plant ## Manufactured in our own plant This part is cold-formed, threaded, heat-treated and finished in-house. The stages below are where its class and finish are actually decided. 1. ![Wire rod feeding into a cold heading machine](https://engineeringhardware.com/wp-content/uploads/2026/08/09-wire-rod-feed-cold-heading-machine.webp) 01 **Cold heading** Wire rod is drawn to size and cold-formed into blanks. Forming rather than cutting keeps the grain flow continuous around the head, which is where a bolt is most likely to fail. Head dimensions and under-head radius checked at set-up and per shift. 2. ![Thread rolling machine producing bolt threads](https://engineeringhardware.com/wp-content/uploads/2026/08/03-thread-rolling-machine-bolt-production.webp) 02 **Thread rolling** Threads are rolled between hardened dies rather than cut. Rolled threads are stronger in fatigue than cut threads and hold pitch and flank angle far more consistently across a batch. Go / no-go ring gauges to ISO 965 tolerance class 6g. 3. ![Baskets of bolts staged for heat treatment](https://engineeringhardware.com/wp-content/uploads/2026/08/05-heat-treatment-baskets-black-bolts.webp) 03 **Heat treatment** Quench-and-temper brings carbon and alloy steel to the property class ordered — 8.8, 10.9 or 12.9 — with the furnace charge tracked so a finished lot can be traced back to it. Core hardness and tensile tested per lot to ISO 898-1. 4. ![Zinc plated bolts in a treatment basket](https://engineeringhardware.com/wp-content/uploads/2026/08/23-zinc-plated-bolts-treatment-basket.webp) 04 **Surface treatment** Zinc, zinc-nickel, hot-dip galvanizing, black oxide, phosphate and Dacromet, selected against the service environment rather than against the price list. Coating thickness and neutral salt spray hours to ISO 9227. ## Frequently Asked Questions ### What material should Linch Pins (Spring-Leg Retaining Pins) be for outdoor use? For damp, coastal or chemical environments specify A4 (316) stainless or a suitably coated steel. For indoor or dry use, A2 (304) stainless or zinc-plated steel is normally adequate. ### Are Linch Pins (Spring-Leg Retaining Pins) made to a recognized standard? Yes — they are manufactured to Trade series (linch pin), so dimensions are interchangeable between suppliers when you quote the standard on your order. ### What are Linch Pins (Spring-Leg Retaining Pins) used for? Connections made and broken by hand many times, where a threaded fastener would be far too slow. They are supplied to Trade series (linch pin). ### Which industries use Linch Pins (Spring-Leg Retaining Pins)? They are commonly specified in linkages & hinges, machine alignment and general machine building, among other sectors. ### Can I get a quote for Linch Pins (Spring-Leg Retaining Pins) in the size and material I need? Yes. Use the technical drawing and quote form on this page to set the size and options, then send the exact configuration to our team for pricing and lead time. ## Related Pages Product page: [Linch Pins (Spring-Leg Retaining Pins) — specifications & sizes](https://engineeringhardware.com/fastener/linch-pins/) ### Linch Pins (Spring-Leg Retaining Pins) Specification Guides ### Related Fastener Applications