Linch Pins

Linch pins (DIN 6799) are quick-release safety pins with a hinged steel ring. The straight leg passes through a cross-hole, the ring drops over the head and locks against the work face. Removal is by lifting the ring back over the head. Used wherever rapid, tool-free, repeatable retention is needed - trailer drawbar pins, towed implement attachment, agricultural equipment quick-couplers, marine and equestrian hardware.

Also known as: Lynch Pins, Ring Pins, Hitch Pins (when used on a hitch), Quick-Release Pins, Drawbar Pins.

Linch pins are not threaded - they are spring-loaded mechanical-locking pins. The label size is the shaft diameter (typically 4.2mm to 6mm). The ring acts as both the spring lock and the operator's grip for quick removal. Distinct from R-clip humpback pins, which use a bent-wire arm instead of a hinged ring.

GRADES AND MATERIALS

Stainless A4-70 G316 - molybdenum-bearing marine-grade stainless. A4-70 G316 resists corrosion in coastal, marine and outdoor agricultural service where zinc-plated linch pins would corrode quickly. The hinge and ring are also stainless, so the whole assembly survives the same environment. Largely non-magnetic in the annealed condition.

DRIVE AND INSTALLATION

Insert the straight leg through the cross-hole until the head sits flush against the work face. Swing the ring over the head; the ring's spring tension locks the pin against back-out. To remove: lift the ring back over the head and withdraw the leg. No tools required.

The host hole must clear the shaft diameter without excessive play - a tight fit wedges the leg and prevents the ring from snapping over the head; a loose fit lets the assembly rattle. Linch pins are designed for repeated install / remove cycles - expect them to be removed and replaced many times over the equipment's life.

A NOTE ON GALLING

Linch pins are not in continuous loaded contact with the host hole - galling is not a practical concern. Avoid hammering the leg in at an angle; this can deform the head or cross-hole. If insertion requires more than firm hand pressure, the host hole is undersized or out of round - drill / ream to the correct clearance.

LENGTH AND MEASUREMENTS

Linch pins are measured by the straight leg length that passes through the host hole. Match the leg length to the host material thickness plus enough clearance for the ring to swing fully over the head without obstruction.

TECHNICAL RESOURCES

Standard: DIN 6799 - Linch pins. Shaft diameter, leg length, ring dimensions and material spec published in the standard. CAD drawings and spec PDFs linked on each product page.

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