Ball Honing for Pneumatic Cylinders

Pneumatic cylinders are fluid power devices that use a compressed gas such as air to move a piston in a reciprocating, up-and-down or back-and-forth linear motion. In double-acting cylinders (DAC), pressure causes the piston to extend and then retract. In single-acting cylinders (SAC), the compressed gas forces the piston in only one direction, typically outward, and a spring provides the return motion.

Other air cylinder designs are available, too, but all fluid power systems require proper maintenance for smooth operation. In a Machinery Lubrication article called Why Air Cylinders Fail, a pneumatics expert explains how “catastrophic failure can occur when cylinder seals have insufficient lubrication.” Although some industrial buyers are now choosing so-called “non-lube” cylinders, seal failure remains a concern.

If the walls of a pneumatic cylinder are too smooth, there’s higher adhesion friction between the O-rings and bore surfaces. In addition, the absence of oil-retaining grooves can affect lubrication. If the walls of a pneumatic cylinder are too rough, burrs and other surface irregularities can shear softer seal materials such as rubber. If seal failure occurs, pressure may be lost and air cylinder performance can suffer.

Deburring and Cylinder Surface Finishing

To protect the integrity of pneumatic systems, manufacturers and maintenance personnel alike need to ensure that bores have a proper surface finish. The Flex-Hone® tool from Brush Research Manufacturing (BRM) removes burrs and improves surface condition at the same time. Suitable for any type or size cylinder, these flexible honing tools also impart a series of oil-retaining grooves for optimum lubrication.

As BRM’s Gold Booklet explains, the Flex-Hone® produces a crosshatch pattern of evenly-spaced “valleys”. Flexible cylinder hones also remove torn, cut, folded, and jagged metal while reducing raised areas or “peaks” to a uniform height. With their distinctive abrasive globules, BRM ball hones use a soft, low-temperature, low-pressure cutting action for superior plateau surface finishing and burr removal.

Flexible hones also feature a double-wire metal stem for easy mounting in handheld power tools or production machinery. As this YouTube video about ball honing a pneumatic cylinder shows, use the Flex-Hone® with a good-quality cutting fluid or honing oil. Because BRM ball honing tools are self-centering, self-aligning to the bore, and self-compensating for wear, no special training is required.

Rotate the Tool or Rotate the Part

The Flex-Hone® Resource Guide provides information about tool selection as well as guidelines for use.   Although general speed ranges are given, machine trials are required to verify parameters. In general, however, users need to remember that flexible cylinder hones are low RPM tools, and that revolutions per minute (RPM) is dependent upon tool diameter.

BRM cylinder hones should be rotated prior to entering the cylinder, and should continue rotating until fully removed from the part. Typically, users secure the Flex-Hone® in a collet, chuck, or similar holding device and then rotate the tool along with the spindle. As this short YouTube video shows, however, it’s also possible to rotate the part instead.

By using flexible honing tools, pneumatic cylinder manufacturers and plant maintenance personnel can remove burrs, improve surface finish, and promote optimum lubrication. Flex-Hone® tools are proudly Made in the USA, and come in a wide variety of abrasive types, grit sizes, and tool diameters for fluid power and other commercial and industrial applications. For more information, visit the BRM website.