This Dowel Former is for 1/4".5/16",3/8",1/2" stock. Get a tighter, more precise fit by making fluted, chamfered dowels. Flutes give the glue somewhere to go and chamfers guide the dowel into the hole.
Cut off a length of dowel, chamfer one end in the included sharpener and bash the thing through the appropriate die.
Flutes are compressed, not cut. For accurate dowel sizes, this is the tool to use.