Carpenters frequently use dowel pins for fastening wood, but dowels have many other industrial applications. Common dowel materials include wood, plastic and metal, and manufacturers produce straight, stepped and tapered ones. Tapered dowel pins, also called taper pins, have a small end, called the point, and a large end, called the head. When forced into a joint, they form a strong connection, but access to the point allows for easy removal with a few light taps. The hole for a taper pin must also be tapered, and you can create such a hole with a reamer or with drill bits.
Drill a hole in the joint to be fastened with a drill bit that is the same size as the point of a taper pin. If you have a metal pin that cannot be easily cut, make the depth of the hole the same as the length of the pin. If the pin is wood, you can make the hole a little shallower and cut off the head of the pin after you have tapped it in.
Widen the hole with a taper pin reamer that has the same taper as the pin. The usual taper is 1/4 inch per foot. Attach the reamer to your drill and drill into the hole until the point of the reamer has reached the end.
Use a succession of increasingly larger-diameter drill bits to taper the hole if you don't have a reamer. Gauge the diameter of each bit, and the depth you drill with it, to produce a hole that tapers with the same angle as the pin. You can create a suitable hole using three or four drill bits in this way.
Spread glue on the pin if you plan to make a permanent connection. Omit the glue if you want to be able to tap the pin out and separate the joint.
Tap the pin into the hole with a hammer. If the hole is the same depth as the pin, tap until the head of the pin is flush with the surface you are joining. If the hole is shallower, tap until the pin is firmly lodged in place, then cut off the end with a handsaw.
For extra holding power, use taper pins with a threaded point.
Taper pins expand and contract with temperature, and they may slip out of the joint in extremely cold conditions. They may also work loose when holding a joint that is moving or vibrating.