A sine vise is a special-purpose vise designed for holding work at a very accurate angle. A sine vise is not rigid enough for every-day work. It’s called a sine vise because you calculate the sine of the angle you want when you set up the vise. The sine vise is a screwless vise that sits on two cylinders. One cylinder is the axis of rotation of the vise body. The second cylinder is positioned very precisely at a known distance from the axis of rotation.