Preform made of ductile material comprising lines of weakness and use of the preform
摘要
<p>Between the tips (2a,2b) of a pair of wedge-shaped longitudinal grooves (2,3) worked up without cutting there is a thin bridge (4) left that can be easily broken off with little force without deforming it by cutting. The depth (d) of the bridge is small in comparison with the depth (D) of a semi-finished wrought product (1) so that the thin bridge can be easily broken off.</p>
