Archery has been around for over 60,000 years. For much of that time bows and arrows were used for hunting. Today, archery is still used in hunting, but also in competition. Archery tournaments feature both individuals or teams and are often split into different rankings. The types of bows used can be barebow, compound, or recurve. Bow designs have come a long way, but so has the arrow. 

In a redesign of a serious hunting arrowhead designed and manufactured by a well-known sporting goods company originally incorporated the use of a Slotted Spring Pin as a pivot for two folding blades in the center of the arrow assembly. It was found that the Slotted Pins bent upon impact, which resulted in a dysfunctional head. This also made the removal of the pin during servicing extremely difficult. 

What the manufacturer needed was a pin that didn’t bend under impact, while simultaneously allowing the blades to pivot freely around it. In addition, they wanted the hunter to be able to service the assembly while in the field. Therefore, the pin had to be able to be easily removed and reinstalled multiple times and still maintain the necessary retention. 

After careful analysis and a comprehensive evaluation of the design and serviceability requirements of the company, SPIROL Engineering came up with a solution. They recommended a full-length Helical Knurled Solid Pin, manufactured from stainless steel, be incorporated in the design as a replacement pin. 

By the nature of its design, this Solid Knurled Pin does not require tight tolerances on the ferrule’s holes for retention. The knurls of the pin remain securely engaged in the host material to ensure that the assembly stays intact during use. The Solid Pin also provides the necessary strength to eliminate bending upon impact. 

Knurled Solid Pins are available with straight knurls and helical knurls. Although the straight Knurled Pins have lower insertion forces, they provide limited retention when axially loaded. The helical knurl allows the pin to rotate as it enters the hole, creating more surface contact with the host. This results in higher frictional forces, greater engagement, and improved resistance to back out. 

The SPIROL Helical Knurled Pin can be removed and reinstalled simply by using needle nose pliers and a small hammer or striking tool. An additional benefit of using this pin is that the clearance between the hole in the blades and outer diameter of the Knurl Pin is minimal, which provides a very robust feel to the assembly. Furthermore, the Helical Knurled Pin was the most cost-effective solution, providing the required retention, resistance to bending, and the ability for the hunter to remove and replace the pin using basic hand tools.

Inside the mechanical aspects of compound bows:

*Lead image from DepositePhotos.com.

For information: 

SPIROL 

Knurled Solid Pin