turtle

In a type-revolving cylinder press, the turtle is the curved, semi-cylindrical plate that holds the letterpress forme (the assembled type and spacing material) during the print run. As the press cylinder rotates, the turtle brings the locked-up forme into contact with the impression roller at the correct pressure and angle. The turtle's curvature matches the radius of the main cylinder, so the forme stays pressed firmly against it without shifting or rocking.

The turtle is typically cast iron or steel, weighing anywhere from 50 to several hundred pounds depending on the press size. It is bolted or clamped securely to the cylinder's body and can be removed for forme changes or maintenance. The working surface must be smooth and flat to within tight tolerances, otherwise the impression will be uneven across the printed sheet. Over time, repeated clamping and the pressure of thousands of impressions can wear or scar the turtle's face.

Variants and limitations

Different press models use turtles of different dimensions and attachment methods. Some older presses have turtles that are integral to the cylinder casting; others use replaceable beds. The turtle's width must match or exceed the widest forme that the press is designed to handle. If a forme is narrower than the turtle, it must be centered and locked down with furniture and quoins to prevent movement during impression.

The name likely derives from the turtle's domed, rounded shape, which resembles a turtle shell. In some older printing texts and manuals, particularly British ones, it may also be called the bed or chase bed, though those terms are more general. Understanding the turtle's role is essential for anyone who operates or maintains a cylinder press, because a damaged or misaligned turtle will cause poor ink transfer, sheet slippage, and damage to type.