Improving Mill Performance Through Bearing, Shaft, and Setup Corrections

Over the years, Roll-Kraft has conducted thousands of mill evaluations on a variety of equipment. We are now sharing these stories in our Tube & Pipe Field Service Report Article Series. We hope you find the information contained in this series helpful. If you have any questions regarding your mill, use our contact form to request more information about our on-site mill evaluation.

Problem: 
During a field service and training session, a tube mill was evaluated after operators reported recurring setup inconsistencies, bearing failures, and product straightness issues. The operators were skilled and resourceful, but their troubleshooting methods relied heavily on personal feel rather than repeatable measurement practices. The request was for an objective evaluation of the equipment condition and setup methodology to reduce scrap and improve consistency.

Challenge: 
The evaluation revealed a number of mechanical issues throughout the breakdown and sizing sections. Entry guide rolls were heavily grooved, worn, and lacking the proper number of rolls to adequately control strip camber at the mill entrance. Multiple driven shafts across the breakdown passes were undersized beyond recommended tolerances, with some more than .003” below spec. Bearings and bearing blocks were frequently loose or damaged, contributing to shaft instability. Operators were unaware that manufacturer-recommended preload torque values existed for setting bearings, leading to additional movement and premature wear.

Tooling inspection confirmed alignment issues. On one set, side-to-side strip thickness varied by nearly .015” in pass 6 due to stand misalignment — requiring over 1/8” of shimming to correct. Some side rolls had been oversized and were not usable, limiting the operators’ ability to control formation. Additionally, the distance between the last sizing stand and the turkshead was unnecessarily long, making tube straightening more difficult and time-consuming.

Training observations also revealed inconsistent use of setup aids. While solder checks and micrometer readings were introduced during the session, operators had historically relied on rim gaps and feel alone. Without consistent measurement practices, setup variation was inevitable.

Solution: 
Roll-Kraft provided both immediate corrective actions and long-term recommendations. Entry guide rolls were to be replaced and the unit upgraded to include four rolls for improved strip stability. Bearing blocks and bearings were recommended for repair or replacement, with strict adherence to inch-pound preload values to reduce movement and extend life. Any driven shafts more than .002” undersize (on 2.000” diameter) were flagged for chroming or replacement to restore proper fits.

Setup methodology was modernized through the introduction of solder pressure checks in each breakdown pass to ensure consistent strip growth and load distribution. Operators were trained to verify roll parallelism with straight edges and to measure strip profiles at the exit side of rolls for accuracy. Roll-Kraft emphasized the use of setup plugs in weld boxes and turksheads to minimize scrap and reduce adjustment time.

Structural recommendations included eliminating an unnecessary seam guide stand, relocating the turkshead closer to the final sizing pass to improve straightness control, and reviewing tooling design. While “W” style tooling was being used, Roll-Kraft advised that conventional edgeform designs may reduce hardness issues and speed mismatches in certain applications.

Together, these corrections and procedural improvements provided a roadmap for more consistent mill performance, reduced downtime, and improved weld integrity.

Contact Roll-Kraft for a Tube & Pipe Mill Evaluation
Do you have issues you would like a second opinion on regarding your mill? Roll-Kraft on-site evaluations really make an impression with your staff, confirming you are serious about producing quality tube, pipe, and roll form products. Our technicians will tell you exactly where you are currently doing a great job, in addition to pointing out any areas that could be improved. We have been doing training and evaluations for over 30 years and understand the sensitive nature of bringing someone in to talk about improvements. Your staff will be in good hands with Roll-Kraft. Click here to learn more about our tube & pipe evaluation service.