Taking on the big bores
January 1st 2009

When it comes to manufacturing, rebuilding or servicing large pumps,valves and cylinder bores, flexible honing can make a difference to performance and service life.One device,the ball-style hone,provides an efficient and portable solution says Brush Research Manufacturing

Overhauling big diesel engines or servicing big pumps and valves means dealing with big bores. If the ID of those bores is not cleaned or resurfaced correctly, the consequences are likely to be lower operating hours between overhauls or degraded performance.

"With hydraulic and hydronic pumps and valves used in mills, petrochemical plants and process industries, critical tolerances sometimes similar to those of internal combustion engines apply to pumps of many styles and applications," says Patrick Sullivan, a facilities management consultant.

One of the most versatile tools to perform maintenance on cylindrical IDs is the flexible ball-style hone. This tool is characterised by abrasive globules that are permanently mounted to flexible filaments attached to a center shaft. This flexible, low-cost tool can be used for sophisticated surfacing, deburring, edge-blending, cleaning and rebuilding of cylinder IDs.

The flexible ball-style hone cleans out passages or provide IDs with a highly efficient plateau finish free of cut, torn and folded metal. Plateau finishing is a process that removes loose, cut, torn and folded material on the surface of the cylinder, maintains valley depth for oil retention and removes peaks that would otherwise damage rings or seals. The process produces a surface with greater bearing area which increases both the life of the cylinders and the piston rings. The result is that more lubricant is retained with less seal wear, improving engine efficiency and performance.

"The trouble you run into is that no two plateauing scenarios are alike," explains Jim Huffman, director of engineering, Salem Tools, a provider of abrasives and engineered manufacturing industry products and value-added services in Salem. "Frequently there's a finishing problem.

The bore is either too smooth or too rough. Ballhoning will eliminate such problems so long as the tool is adjusted to meet the requirement of the individual application." Available in various grit sizes and diameters up to 50- plus inches (4 mm to 36 inches are standard sizes), Brush Research Manufacturing (BRM) offers a line of Flex- Hones that are suited to heavy-duty applications.

"The unique design of the Flex-Hone allows it to pass over the ports, smoothing down all the rough spots," Clarence Mayers, coordinator for Diesel Supply Company (Odessa, Texas) explains. "The firing pressure in the combustion chamber causes the rings to load from the back side pushing out against the cylinder wall. This style of hone smoothes out all of the rough spots around the ports or any other part of the cylinder liner walls - top to bottom." In the process of thoroughly cleaning and resurface cylinder liners from top to bottom, some hones could get hung up. However, a large flexible hone can be used without any such snags.

"Getting top-to-bottom cylinder or liner wall coverage is difficult to do with other tools,"Mayer says. "The flexible hones that we deal with are probably 12-18 inches wide. So, if you run it two or three inches past the bottom of the liner, that's not a problem.

Most of the hone is still inside the cylinder, so it can go down and complete the bottom of the piston travel area. The same applies to the top of the liner, where it gets chamfered because of where the top ring travel ends. The Flex-Hone can blend that area quite easily." Whether used for cleaning, de-burring or plateau finishing, this tool provides a lowtemperature abrading process that exposes the undisturbed base metal structure to produce a long wearing surface.

Available in various grits and sizes, the Flex-Hone is a resilient, flexible, honing tool with a soft cutting action. The abrasive globules each have independent suspension that is self-centering, self-aligning to the bore, and self-compensating for wear, all of which facilitate close-tolerance finishing work.

Established in 1958, Brush Research Manufacturing has been solving difficult finishing problems with brushing technology in the environments of nuclear energy, aerospace and computer technology as well as industrial applications. For more information visit the web site www.brushresearch.com, or contact UK distributor Pacehigh: