Cylinder bores are machined into engine blocks to guide
pistons, seal combustion chambers, and aid in engine cooling. In aluminum
engines, bores may be chrome-plated or fitted with cast iron sleeves or liners to
prevent excessive wear. Over time, however, repeated contact between the piston
rings and cylinder walls may cause scoring, glazing,
or the development of cylinder ridges.
To restore used engines to peak performance, engine remanufacturers
and rebuilders must determine whether cylinders bores can be reconditioned. If the
bores can be reused, a flexible hone provides a quick, efficient, and easy-to-use
way to recondition the bores in both large and small engines.
Inspecting and
Measuring Cylinder Bores
In "Evaluating the Cylinder," an analysis of cylinder
reconditioning methods, the Small Engine Information
website explains how to inspect and measure cylinder bores. If a visual
inspection reveals that a cylinder wall has score marks, measure the size of
the bore and also the roundness and taper. Then compare these measurements to
specifications in your engine service manual for maximum wear limit, maximum
out of round, and maximum taper allowed.
Honing Engine
Cylinders
If cylinder wall scoring is non-existent or shallow, and all bore measurements
are within tolerance, your engine cylinder does not need to be machined to a
larger size and fitted with oversized pistons. Before reassembling your engine,
however, cylinder reconditioning is recommended. For best results, use a
Flex-Hone tool to hone the cylinder walls. Built with a stiff, coated stem and finger-like formations of
abrasive globules, this flexible engine hone follows the geometry of the bore to create a uniform surface
finish that promotes optimum lubrication.
Flexible Hones vs. Rigid Hones
Flexible hones produce a controlled surface condition and create a cross-hatched pattern that's
extremely efficient at creating grooves for oil retention. By contrast, rigid
hones or honing stones create unidirectional or uneven grooves that may interfere
with optimum lubrication. Available in a variety of sizes, flexible hones are used with large diesel engines, small two-stroke engines, and by automotive manufacturers and hobbyists alike.
Author's Note: This CR4 blog entry originally appeared in BRM's Flex-Hone Blog.
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