Flexible cylinder honing

Taking on the big bores

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

The ball style hone, an inexpensive yet sophisticated device, is used for deburring, plateau honing and deglazing. This precision-quality Flex Hone from Brush Research Manufacturing not only deburrs bored metal, it also easily removes even microscopic metal shards and fragments.

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

For example, after installation in the field, valves and pumps often require maintenance to clean IDs of foreign material, ranging from rust and corrosion to accumulated chemicals and biological matter.

“Critical tolerances, some similar to those of internal combustion engines, apply to the hydraulic and hydronic pumps and valves used in mills, petrochemical plants and process industries,” says Patrick Sullivan, a veteran facilities management consultant.

One of the most versatile and easy-to-use tools used throughout industry today to perform maintenance on cylindrical IDs is the flexible ball-style hone. Somewhat resembling a spinning bottlebrush, this tool is characterized by abrasive globules that are permanently mounted to flexible filaments which are attached to a center shaft. This extremely flexible, low-cost tool can be used virtually anywhere for sophisticated surfacing, de-burring, edge-blending, cleaning and rebuilding of cylinder IDs.

“In chemical, refining and wastewater operations, honing may be required to remove corrosion or the formation of clay, wax or other solids and may prevent proper valve operation or block lubricants,” Sullivan says.

For big bore engines used in rail, earthmoving, shipping and mining operations, it is crucial to the service life that the cylinder liner walls be deglazed, refinished and crosshatched when these engines are overhauled.

The engines powering big oceangoing vessels, such as tankers and freighters, are popular applications for large-bore flexible hones. Marine service shops that perform maintenance on big ship engines are often scheduled to service them as soon as the vessels come into port.

“These engines have pistons as wide as your hat,” states Clarence Mayers, coordinator for Diesel Supply Company (Odessa, Texas). “We sell ball-style hones to users and repair shops who overhaul the big bore diesels and natural gas engines so they can get a longer service life cycle. Mainly, they are used on cylinder liner walls so new rings can seat properly and prevent excessive oil consumption.”

The flexible ball-style hone produces a controlled surface condition that is unobtainable by any other method. It can de-burr, clean out passages or provide IDs with a highly efficient plateau finish free of cut, torn and folded metal.

Plateau finishing
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 both 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 Inc., a provider of abrasives and engineered manufacturing industry products and value-added services in Salem, Va. “Frequently there’s a finishing problem. The bore is either too smooth or too rough. Ball-honing will eliminate such problems so long as the tool is adjusted to meet the requirement of the individual application.”

Although large-diameter flexible ball-style hones are somewhat unique, they are needed to resurface liners and cylinder bores in larger engines such as the Worthington, Clark, Ingersoll-Rand and Cooper-Bessemer models used for heavy-duty applications, as well as ElectroMotive-type engines used by the rail industry.

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 uniquely suited to heavy-duty applications.

Mayers also points out that the flexible hone does an especially good job of clearing the ports on 2-cycle engine liners. Another type of hone can get hung in the port area and break off honing material causing havoc when the engine is operated. If the port areas are not relieved, the installed rings can get into the ports and clip the rings ends, thus breaking off the ends and causing severe damage to the engine. This is called port clipping.

“The unique design of the Flex-Hone allows it to pass over the ports, smoothing down all the rough spots,” Mayers 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 resurfacing cylinder liners from top to bottom, some hones could get hung up. However, a large flexible hone can be used without any such snags.

Buildup of wax or other solids may prevent proper valve operations or block lubricants. Proper maintenance tools like the Flex Hone leave a super smooth plateau finish.

“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 low-temperature abrading process that exposes the undisturbed base metal structure to produce a long wearing surface.

This flexible ball-style hone features a unique design which also makes it ideal for just about any application that calls for the use of a resilient, flexible and soft-cutting honing solution.

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 sophisticated environments of nuclear energy, aerospace and computer technology, as well as industrial applications.

This article appeared in the June/July 2008 issue of MRO Today magazine. Copyright 2008.

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