Determining the Ratio of the Gearbox and Tooling in the Breakdown Section: Roll-Kraft Quick Tips Article Series

Welcome to our Roll-Kraft Quick Tips article series. Drawing from Roll-Kraft's Tube and Pipe Technical Tips video series, these articles bring together practical advice, proven setup techniques, and maintenance best practices that can help improve mill performance and product consistency.

In our first article, we’ll be focusing on Determining the Ratio of the Gearbox and Tooling in the Breakdown Section.

Many tube and pipe mills utilize unequal top and bottom roll diameters in the breakdown section. To accommodate these differences, the gearbox ratio must match the tooling ratio. When these ratios do not match, the mill can experience a variety of operational issues, including tiger striping on the rolls, material marking, surging, and premature tooling wear.

Determining the tooling ratio is relatively straightforward. When tooling prints are available, the ratio can often be calculated directly from the documented roll diameters. When prints are unavailable, the throat diameter of both the top and bottom rolls can be measured at the drive point. Dividing the smaller diameter into the larger diameter provides the tooling ratio.

The gearbox ratio can often be identified from prints, gearbox markings, or by inspecting the transfer gears. When those options are unavailable, ratio wheels can be used to compare shaft rotation and determine the actual ratio present in the gearbox.
Maintaining a proper match between gearbox and tooling ratios helps ensure smooth mill operation, reduces unnecessary wear, and improves product consistency.

Watch our video below for a full demonstration:

Have questions about your tube mill setup process or need help troubleshooting a production issue? Roll-Kraft provides tube and pipe tooling design, technical support, setup assistance, and project quoting support for manufacturers worldwide. Visit our Contact Us page to speak with our team about your application, tooling requirements, or production challenges.