The shell of this helical broach (1) is formed by stacking a plurality of wafer shells (20.sub.W(1)-20.sub.W(N)) in the axial direction, and is obtained by forming on the wafer shells (20.sub.W(1)-20.sub.W(N)) finishing blades (30.sub.W(1)-30.sub.W(N)) corresponding to teeth grooves on a piece to be cut (W) and forming the finishing blades (30.sub.W(1)-30.sub.W(N)) such that the blade width gradually increases with each of the aforementioned wafer shells (20.sub.W(1)-20.sub.W(N)) from the leading end of the cutting direction toward the trailing end of the cutting direction.

The finishing part (4) of this helical broach (1) is formed by a first shell (20) and a second shell (30) which are divided in the axial direction, and is obtained by forming a first finishing blade (50), which comprises a prescribed gear tooth helix angle () end a first blade groove helix angle (.sub.1), on the aforementioned first shell (20) and forming a second finishing blade (60), which comprises the aforementioned prescribed gear tooth helix angle () and a second blade groove helix angle (.sub.2) which differs from the aforementioned first blade groove helix angle (.sub.1), on the aforementioned second shell (30).

The finishing part (4) of this helical broach (1) is formed by a first shell (20) and a second shell (30) which are divided in the axial direction, and is obtained by forming a first finishing blade (50), which comprises a prescribed gear tooth helix angle () end a first blade groove helix angle (.sub.1), on the aforementioned first shell (20) and forming a second finishing blade (60), which comprises the aforementioned prescribed gear tooth helix angle () and a second blade groove helix angle (.sub.2) which differs from the aforementioned first blade groove helix angle (.sub.1), on the aforementioned second shell (30).

A machine tool includes a fixed pillar, a finishing cutting tool with a first teeth portion, a rough cutting tool with a second teeth portion, a punching tool with a third teeth portion, and a support member passing through the punching tool, the rough cutting tool, and the finishing cutting tool and detachably mounted to the fixed pillar. The finishing cutting tool, the rough cutting tool, and the punching tool are arranged sequentially in a direction away from the fixed pillar. The outer diameter of the fixed pillar is smaller than the diameter of the finishing cutting tool. The diameter of the finishing cutting tool is greater than the diameter of the rough cutting tool. The diameter of the rough cutting tool is greater than the diameter of the punching tool. The present invention further provides a method of machining a box-end wrench by using the aforesaid machining tool.