Written by Jody Muelaner
There are many types of pins used as fasteners. At its simplest, a dowel pin is just a solid cylinder of material, which is inserted through a hole.
When a dowel pin is inserted through concentric holes in two or more components, it locates and holds them together. A slight interference or transitional fit is typically used, which compresses the pin and generates significant friction to hold the pin securely in the holes.
Steel dowel pins are often used in precision engineering applications for accurate location and alignment. These dowels have chamfers at each end to enable insertion and to guide alignment. This type of dowel is also available in other metals and engineering grade polymers.
Alternatives to steel dowel pins include roll pins (slotted or spiral), grooved pins and cotter pins. Dowel pins are usually the most precise but may not be the easiest to insert and remove. Wooden dowels are widely used within joinery, as well as traditional methods of timber frame construction and shipbuilding. These dowels may be supplied as a length of a “dowel rod” from which individual dowels of the required length can be cut.
Pre-cut dowels are also available, these normally have chamfers at each end, for the same reasons as steel dowels.
If a smooth wooden dowel is driven into a tight interference-fit hole it can form an air-tight seal, particularly if it’s coated in a layer of glue. When driving dowels into blind holes, air and glue becomes trapped in the hole and significant pressure can be created. This can prevent dowel insertion or split wooden parts.
When cutting dowels from smooth dowel rod, a flat can be planed on one side to relieve this pressure. Pre-cut dowels often have flutes for the same purpose.
As an alternative to using wooden dowels, biscuit joints or mortise and tenon joints may be used. An advantage of dowels is that they only require a simple round hole to be drilled.