There are many ways to align components – the challenge for Design Engineers is choosing the best solution at the lowest cost. The most common, and often most expensive, Alignment Dowels are manufactured in accordance with ISO 8734. These precision ground “parallel” pins provide excellent positional tolerance at a cost. Ground Dowels require extremely tight hole tolerances. In addition, this solution is typically through hardened for strength or case hardened for wear resistance.

If the pin’s sole purpose is for alignment, the heat treating process adds cost without any functional benefit. Spirol’s GD100 Ground Hollow Dowel is designed to be a direct replacement for Solid Ground Dowels in alignment applications. This lightweight solution will provide the same positional accuracy as Solid Ground Dowels at a fraction of the cost. Like their solid counterparts, GD100 Hollow Dowels are precision ground and require the same hole tolerances for proper installation and retention. The GD100 is approximately 50% lighter than a Solid Dowel – an important consideration for cost conscious Design Engineers seeking weight reduction without sacrificing performance. The lower weight will also translate into significant savings in transportation charges.

Although Spring Alignment Dowels, Dowel Bushings, and Coiled Spring Pins are not precision ground, they are still capable of accurately projecting hole position for the purpose of alignment. Each of these options is designed to be larger than the hole in which it is retained. The mechanism of retention is compression rather than interference, so hole tolerances can be relaxed and secondary reaming operations can be eliminated to reduce manufacturing costs. The flexibility of these parts also provides much lower insertion force than is required for Ground Solid or Ground Hollow Dowels. The spring characteristics of these parts absorb wide hole tolerances, reduce manufacturing costs, and dramatically reduce component cost when compared to Solid Dowels.

Spring Alignment Dowels and Coiled Pins are often used to accurately position one component to another. Spring Dowels are generally recommended for applications requiring a “dowel” with a length to diameter ratio of 1.5:1 to 4:1. Coiled Pins are generally recommended in applications with greater length to diameter ratios between 4:1 to 10:1. In applications requiring bolts for axial retention, further savings can be achieved by passing the bolt through the inside diameter of a Dowel Bushing. This eliminates the cost associated with drilling a separate hole for the bolt. Dowel Bushings are also hardened to protect the bolt from shear loads, and isolate the forces on the bolt to tension loading to ensure joint integrity.

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