A dowel screw is a cylindrical metal fastener with two threaded and tapered ends. Two wood screws with their heads cut off that have been welded together at the cut ends form a dowel screw. These screws are often used in furniture and other woodcraft to create a joint with visible connectors. Half the length of the screw is driven into one surface of the joint. The surfaces are aligned at the connection point and spun in place to drive the other half of the screw all the way in.
Rigid parallel grooves on the dowel screw exterior grip and hold the material they are driven into. Most dowel screws are made of steel for increased strength. These screws are available in a wide variety of widths and lengths to meet the requirements of most projects. Many screws are coated in zinc, or galvanized, to protect them from corrosion due to moisture exposure.
The installation of a dowel screw cannot be done with a common screwdriver. Dowel screws are generally driven into previously drilled guide holes that are slightly narrower and shorter. Holding the screws with a pair of pliers or vise grips may flatten the threads and render the fastener useless. Specialized dowel screw driver heads are designed to sink the fastener into a surface without crushing the threads. Multiple dowel screws on the same joint share the weight load and increase the strength of the juncture.
Dowels screws are sometimes included with self-assembly furniture. These fasteners are generally designed to be twisted in by hand without the use of any tools. Instructions for assembly may also include adding a small amount of wood glue to the guide hole before driving in dowel screws. The screws are ready to install into the adjacent surface once the wood glue has dried. Overdriving a dowel screw into the particle board used in inexpensive furniture may cause cracks that decrease the stability of the piece.
Removal difficulty is greatly increased once the dowel screw has been installed in both joint surfaces. Using brute force to pull the connection apart usually causes damage to one or both of the connected pieces. Dowel screws can usually be carefully filled or sawed in half to sever a connection without causing a break. The protruding section of each half can then be gripped with pliers and twisted out completely.