Coiled Spring Pins are manufactured with a seam which is much better for hinges than the gap or slot of Slotted Spring Pins.  The seam is inherent to Coiled Pins because they are rolled with more than one wrap of material.  The Coiled Pin’s “duty” will affect material thickness and the coil configuration but all Coiled Pins will possess a seam.

Some assume that a Coiled Pin’s seam is raised above the surface of the pin.  This is not the case.  A Coiled Pin’s seam is actually ‘tucked’ or rolled to ensure the pin remains round.  In addition, the seam is prepared with a bevelled edge to soften the transition into the ‘comma’ area.  In fact, a key characteristic of a properly rolled Coiled Pin is that the diameter of the pin at the seam is equal to or less than the diameter adjacent to the seam.  This prevents the edge of the material from contacting the inside diameter of the hole wall and prevent skiving when inserted.

A large percentage of Coiled Pins are used in hinges and the unique seam configuration is essential to their proper function.  Thus, when utilized in round holes, the seam should have absolutely no impact on performance.

The Coiled Pin’s tucked seam will allow smooth, interference-free rotation of hinge/axle components in the vast majority of assemblies.  In most situations where the seam is problematic, it is typically the result of poor installation methods or improper

implementation.  If excessive compressive force is applied to one part of the pin and not another, seam deformation may occur.  This sometimes happens when assemblies are designed such that they do not properly support the pin.  Similarly, pins can be damaged during installation and this can lead to deformation at the seam.  Improper installation technique, equipment, hole condition, or pin material and duty are typical causes.  Designers have also attempted to use Coiled Pins and Slotted Pins in assemblies where a ‘pawl’ or lever must ride axially on the surface of the pin as it rotates.  The geometry of these components sometimes causes them to catch or ‘hang up’ on the seam.

For more information, contact Spirol Industries Ltd, Princewood Road, Corby, Northants, NN17 4ET, Tel:  +44 (0) 1536 444800, Fax: +44 (0) 1536 203415,

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