Fracture modes of wood in mechanical joints with a single stiff bolt loaded parallel to the grain were experimentally investigated. For the end margin less than two to four times the bolt diameter, the ultimate state was governed by premature failure either of end transverse tensile or push-out shearing fracture in a brittle manner. For the end margin greater than that, the ultimate state was by splitting fracture, and the maximum strength kept nearly constant due to bearing yield of wood underneath the bolt, in that the embedding deformation up to the fracture increased with the end margin. The circumferential friction acting on the contact arc between bolt and wood gave a moderate effect such that the frictional coefficient enhanced the joint ductility as well as strength. The support condition in the opposite side of the test joint showed little effect on the ultimate behaviors.
