1/4 x 3/4 Dowel Pin Alloy Steel. Dowel pins are solid, headless straight pins with a closely controlled diameter. They are widely used as plug gages, hinges or shafts. The precise tolerances in dowel pins make them excellent for achieving proper alignment of parts in high speed assemblies or as roller bearing in bus and truck wheel assemblies. Dowel pins should be installed by being pressed in, not struck with an impact force.