US Patent 7214021 Helical grooved pin

A helical grooved pin for insertion into a hole in a hard host material includes a formed portion of helical lands and grooves. Pin material from the grooves is displaced to define lands at an expanded diameter relative to the pin stock material. The forming process employs a rolling die configured to produce substantially uniform cylindrical land surfaces. The helical lands have a width that is at least five times the height of the land. The expanded diameter of the formed portion of the pin is no more than 5% larger than the diameter of the pin stock material. These proportions provide a uniform, durable and reliable retaining surface to the pin which is particularly useful in applications where the host material is harder than the pin.