Metal shears with mechanical advantage

Shears for cutting stiff sheet materials, comprising:

• first and second jaws pivotably interconnected by a jaw joint, the first and second jaws having respective first and second cutting edges located in a forward direction from the jaw joint, the first and second cutting edges arranged to cross one another at a crossing point which moves during a cutting operation, at least one of the cutting edges being curved, the second jaw including an extension extending in a rearward direction from the jaw joint, and first and second handles adapted to be gripped by a user's hand,
• the first handle being rigid with the first jaw,
• the second handle pivotably connected to the first handle by a handle joint located rearwardly of the jaw joint;
• the cutting edges configured to cross one another at a substantially constant angle during a cutting operation;
• the second handle engaging a surface of the extension by a moving contact which is fixed relative to the second handle and movable relative to the extension, the handle joint being located wherein a distance between the jaw joint and the moving contact increases during a cutting operation, the sliding contact disposed rearwardly of the handle joint when the jaws are fully open and fully closed.