Tooling Wear and Setup Discrepancies on Stainless Tube Mill

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 multi-day training and evaluation session, several tube mill lines were reviewed to assess setup consistency, tooling integrity, and mill alignment. Operators had reported weld inconsistencies and out-of-round product on key stainless steel sizes. The root issues appeared to stem from tooling wear and setup discrepancies across the breakdown, fin, and sizing sections.

Challenge: 
One of the primary issues identified was the lack of accurate setup data for many roll sets, particularly in the side pass and fin sections. On one mill, the actual strip width being run was 0.055" narrower than required, resulting in inadequate material presentation to the fin blades. Several fin passes were not even contacting the strip edges, allowing the profile to grow through the section rather than be worked as intended.

Roll-Kraft also discovered that many rolls, especially in the fin section, were heavily worn with no usable rim clearance left for adjustment. Several top segmented rolls showed damage near the fin blade area, which was likely contributing to the poor weld profile. Elsewhere on the line, missing drive shafts meant only partial power was being applied to driven rolls, increasing load and wear on the connected shafts and tooling.

Compounding the issues was the use of basic tools like calipers instead of micrometers and the absence of OD solder for pressure checks. Many top tie bars were also either too short or missing altogether, preventing operators from properly paralleling the side rolls.

Solution: 
Recommendations included the immediate update of all setup charts with current tooling geometry, especially in the side pass and fin areas. Roll-Kraft assisted with re-developing charts based on available rework records and drafted profiles where necessary. Operators were trained to verify rim clearances, parallelism, and tube size using micrometers, solder, and straight edges.

It was also advised that all missing drive shafts be replaced to restore full torque transmission across the driven passes, particularly in the fin and sizing sections. Roll sets showing extreme wear were to be reworked or replaced with tooling specifically matched to current gauges and product dimensions.

Finally, damaged weld rolls, side pass stands, and bearing blocks were flagged for repair or retrofit. Roll-Kraft encouraged annual training and follow-up evaluations to maintain setup consistency and prevent future performance gaps.

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