Line Boring: Underrated Yet Crucial Machinery Repair

Maintenance and repairs of vessel machinery is important for safety, efficiency, and longevity. Line boring, when required, is an important process that falls under the repair umbrella and often doesn't get the attention it deserves. This specialized technique is essential for fixing damaged bores or for precision alignment of existing bores on large vessels.

Line boring repairs worn, misaligned, or damaged holes back to smooth uniform cylinders. This is especially important for parts that require alignment measured to the thickness of a single hair for proper operation, such as main bearing bores on engine blocks and strut/stern tube bearing bores to precision fit their respective bearings. The ability to perform line boring directly on the vessel, or in-situ, offers a big advantage. It avoids the need to move large, heavy parts to a shop, which can be impractical and expensive.

The in-situ line boring approach saves time and reduces logistical challenges/expenses related to transporting assets off-site for repairs. Often times, in the case of a vessel’s stern tube, it is impossible to transport to an off-site location. Performing line boring in place doesn’t come without its unique challenges. Generally, an access hatch will need to be opened within the stern tube, forward of the bore to be machined. Depending on the size of the bore, access to install the equipment can be challenging. Finally, the boring bar supports must be precision aligned to avoid machining at an angle and missing your target values and tolerances.

AME was asked to assist a large machining company in aligning the boring bars which were set to repair the forward and aft stern tube bearing bores of a large cargo ship. It was the perfect opportunity to break out our FARO Vantage laser tracker! Using this powerful equipment, measurements of all the bearing bores were measured and captured in a 3D software. The boring bar supports were then measured, captured in the software, and compared to the optimal alignment reference line. Adjustments were made so the boring bar was in line with the alignment reference, and once locked in, the cutting began.

Line boring ensures the proper functioning of machinery, reducing the risk of breakdowns that can cause expensive delays or dangerous situations at sea. It also prolongs the life of critical assets by delaying replacement of major components such as engine blocks, struts, and stern tubes. In addition, keeping machinery properly aligned significantly increases fuel efficiency, saving money and minimizing environmental impact.