All Spring Pins have the common characteristic of a pin diameter larger than the hole diameter into which the pin is installed. Coiled Pins can be easily identified by the 2.1 /4 coil cross-section. The absence of a slot eliminates pin nesting and interlocking. When Spiral Coiled Pins are installed, the compression starts at the outer edge and moves through the coils toward the center. SPIROL Coiled Pins spread compressive stress over the entire pin and do not have stress point concentrations. Comparatively, Slotted Pins compress by closing the slot, and stress is concentrated 180 degrees opposite the slot. This imbedded stress at installation, combined with the concentration of stress during the assembly’s life reduces the fatigue life of the Slotted Pin potentially causing premature assembly failure. Solid Pins are retained by compressing and deforming the host material, not the pin. If the Solid Pin has knurls, the knurls cut into the host material during installation. In all instances, the Solid Pin must be harder than the host material or else the pin will be deformed.