Cylinder Hones: The Flex-Hone® vs. Honing Stones

Cylinder honing tools are used to deglaze the walls of cylinders in gasoline and diesel engines. Over time, a piston’s reciprocating movement will polish the cylinder walls to a smooth finish, preventing the piston ring from mating with the cylinder bore and providing an adequate seal. Glazed cylinder walls also cause friction and lubrication problems since engine oil won’t adhere properly to a mirror-smooth surface. The way to break this glaze is with the Flex-Hone®, an engine hone that also promotes optimum lubrication.

Choosing Cylinder Hones for Engine Repairs
Engine Repair Shop.com is an automotive website run by Bill Koustenis, a machine shop owner and self-described “car nut” who recommends cylinder honing tools for “reringing the engine”. A member of the Engine Rebuilders Association (AERA), Koustenis compared traditional stone hones to the Flex-Hone® tool from Brush Research Manufacturing (BRM). Although honing stones are “probably  the oldest and most common type of portable hone,” Koustenis favors the Flex-Hone® for preparing engine cylinders.

Engine Blocks: Problems with Stone Hones
The “problem” with portable honing stones, Koustenis explains, “is that it is impossible to really end up with a straight and round cylinder”. Engine cylinders with excessive wear should be “bored to the next oversize” instead. Engine builders who use honing stones can ruin the engine block, a problem Koustenis has seen “plenty” of times. “I really do not feel,” the former drag racer explains, that stone hones “have any place in quality engine repairs.”

Engine Rebuilds: The Flex-Hone® Solution
Self-centering and self-aligning to the bore, the Flex-Hone® is a flexible, resilient cylinder honing tool with a soft cutting action. Built with a stiff metal stem, flexible nylon strands, and abrasive globules that come in a selection of grits and abrasive types, the Flex-Hone® “removes hardly any material and works great with almost any type of piston ring,” Bill Koustenis explains. He adds, “We use this type of hone when a performance or racing engine is being ‘freshened up’ during the racing season.”

The Flex-Hone® tool from Brush Research Manufacturing (BRM) also promotes optimum lubrication. Unlike rigid hones, which produce uneven or unidirectional grooves, the Flex-Hone® produces a plateau surface finish for improved oil retention. For more information about the importance of a plateaued cylinder wall finish, click here for a free technical book from BRM. It’s one of many in-depth publications available from the Brush Research website.