Patent ID: 8015851

Claim:
A dowel forming method for a buckle base member, comprising: when forming a dowel section by performing press working on each of portions constituting side walls of a buckle base member, using a die of a negative clearance with a punch portion whose length or diameter is larger than a length or diameter of a die portion; and applying compressive stresses involving no deviation in an in-plane direction from above and below to a portion of a workpiece constituting a root of the dowel section, wherein the press working is performed in a dowel section height of (0.70 to 0.95)×t, where t is the plate thickness of the buckle base member, and wherein the relation of a clearance C, a length or outer diameter D 1 of the punch portion, and a length or inner diameter D 2 of the die portion is set in C=(D 2 −D 1 )/2, and the clearance C is a negative.