Sometimes you drill a 1/4″ hole for a 1/4″ dowel pin only to find out that dowel pin is too large for the hole! Most woodworkers try to fix this by reaming the drilled hole with the drill bit. Doing that is a BIG mistake, because that will mess up your dowel joint.
A better solution is to “shrink” the dowel pin just a bit by hammering it through a 1/4″ short pipe nipple. The inner edges of the nipple are sharp enough to cut wood. This trick also works with 3/8″ dowel pins and a 3/8″ short pipe nipple.
– Bruce Kieffer
Edina, Minnesota