Patent ID: 8074482

Claim:
A plug for use in cold drawing of a metal pipe, comprising: a first columnar portion having an outside diameter D 1 ; a second columnar portion formed coaxially with the first columnar portion and having an outside diameter D 2 larger than the outside diameter D 1 ; and a tapered portion formed between the first columnar portion and the second columnar portion and having a tapered surface provided with an outside diameter gradually increasing from the first columnar portion to the second columnar portion and an axial direction length L, the outside diameters D 1 and D 2 , and the axial direction length L meeting the following expressions (1) to (4): 0.25≦ρ≦2.00 (1), 0.06 ≦L/D 2≦0.8 (2), L/D 2≦0.3×ρ+0.575 (3), and L/D 2≧0.1×ρ (4) where ρ=( D 2 −D 1)/ D 1×100.