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Brush Research Manufacturing (BRM) supplies flexible cylinder honing tools for bores
with diameters as small as 4mm and as large as 36". A flexible, resilient
honing tool, the Flex-Hone is
self-centering, self-aligning to the bore, and self-compensating for wear. Flexible
hones improve surface finish and remove burrs at the same time, and can be used
in either handheld power tools or machine centers. Known also as ball hones, these brushing tools feature
abrasive globules permanently laminated to flexible nylon filaments.
Cylinder
Hone Diameter
To produce a soft cutting action, Flex-Hone
tools are always used in an oversized condition. This means that a deburring
tool for a 3" bore, although listed as a 3" tool, has
a diameter that's slightly larger than 3". On the BRM website, cylinder hones
are categorized as standard small-diameter (4mm to 3"), standard and heavy-duty
(3" to 18"), and super heavy-duty large-diameter (19" to 36"). Diamond Flex-Hone® tools are
available in 4mm to 1-1/2" diameters and Flex-Hone for chamfer blending tools come in 4mm
to 7/8" diameters.
Rotational
Speed
Diameter is an important specification to
consider not just during brush tool selection, but also during Flex-Hone use. Ball
hone size helps determine the recommended operating speed in revolutions per
minute (RPM). The Flex-Hone
Resource Guide provides some general ranges for rotational speeds, but users
should perform machine trials to test their own equipment against these
guidelines. In general, however, larger tools run at slower speeds and smaller
tools run at faster speeds.
Stroke Rate
Tool diameter also drives another important
operating parameter: stroke rate. This is the number of inches per minute (IPM)
that are fed or stroked during flexible honing operations. Depending on how the Flex-Hone
tool is configured, stroke rate is controlled either by machine parameters or
by a human operator. Stroke rate is also related to the angle of the cross-hatching
on cylinder walls, the tiny oil-retaining grooves that help optimize
lubrication.
Cross-Hatch
Angle
Flex-Hone tools improve cylinder wall surface
quality by imparting a cross-hatch pattern and producing a plateau finish. The angle at which these
cross-hatched lines intersect can vary, and is a function of both stroke rate
and rotational speed. As the Flex-Hone Resource Guide advises, use a slower stroke rate to achieve a smaller
cross-hatch angle (e.g., 20° to
23°). Use a faster stroke rate to achieve a larger
cross-hatch angle (e.g., 45°).
Putting
It All Together
Tool
diameter helps determine the recommended speed, and is related both to stroke
rate and cross-hatch angle. Remember, however, that smaller-diameter Flex-Hone tools require faster stroke rates to achieve the same cross-hatch angle as larger-diameter tools.
Author's
Note:
This CR4 blog entry originally appeared in the BRM
Flex-Hone Blog.
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