A wood threader is a device or combination of devices that can be used to create wooden bolts and threaded holes. These devices can be either semi-automated or completely manual in nature. Semi-automated wood threaders typically make use of a router to cut male threads into a dowel and a tap to create female threads. Manual versions are essentially tap and die sets that are designed specifically for wood. Each wood threader can only cut threads of a certain pitch and diameter, so a kit that contains multiple threaders is necessary in order to work with a variety of dowel sizes.
The simplest type of wood threader is essentially a tap and die set that is designed specifically for use with wood. In a tap and die set, the tap is the component that cuts female threads and the die is used to create male threads. Since threads must be cut into a cylindrical object, wood dowels are typically used for this purpose. In order to use this type of wood threader, the dowel is usually inserted into a vice or jig so that it will stay in place while the threads are cut. The die can then be placed at one end of the dowel and threaded down onto it, cutting new threads as it is turned.
More complex, semi-automated wood threaders perform this same essential function by using a router table. A special router bit and jig can allow an operator to cut precise threads into a dowel as it is passed over the cutting edge. Since this type of wood threader results in the dowel rotating precisely in relationship to how far it has passed over the bit, the operator can typically feed it in as quickly as the router is capable of cutting. This type of wood threader may result in a more precise thread because there is less room for operator error during the procedure.
Both types of wood threaders typically make use of a tap to create female threads. This type of wood tap can be used to either make wooden nuts or cut a threaded hole in a larger piece of wood. One common use is to create tapped holes on the bottom side of a table for the legs to thread into. This is accomplished by first drilling a hole and then slowly threading the tap into it. The sharp edges of the tap are designed to cut precise threads that a threaded dowel can then screw into.