Traditional abrasive machining processes like grinding and rigid honing use lubrication to combat the effects of friction, pressure, and heat. By reducing friction, lubrication keeps both the part and the tool cool. Reduced friction also supports more rapid material removal without damage to the workpiece. Additional benefits of lubrication include longer tool life, more efficient cutting, reduced cycle times, and superior surface finishes.    

Selecting the right lubricant for grinding or rigid honing is a function of multiple factors. Machinists and manufacturers need to consider the composition of the grinding tool, the type of material that’s being finished, material hardness, material removal rate, part geometry, and fixturing. Typically, fluids are characterized by their cooling or lubrication characteristics. 

For traditional abrasive machining processes that employ a great deal of pressure and generate significant amounts of heat, lubricant selection is especially important. It’s also important to use a lubricant with BRM’s Flex-Hone® tools, but for very different reasons.

Why Flexible Honing Requires Lubrication 

Unlike grinding or rigid honing, flexible honing is a low-pressure, low-temperature abrading process. The BRM Flex-Hone® tool’s cutting stones or globules are comprised of virtually 95% pure raw grain abrasive in an epoxy matrix. These abrasive globules or balls are laminated to flexible nylon filaments that help make the Flex-Hone® self-centering and self-aligning to the bore. 

With flexible honing, the pressure against the workpiece is determined by the diameter of the nylon filaments and the degree of oversize between the bore diameter and the hone diameter. As a rule, the Flex-Hone® is always used in an oversized condition. The result is a soft, abrading process that produces very little heat while significantly improving the workpiece’s surface finish. 

If flexible honing doesn’t generate significant amounts of heat, why is a lubricant required? The primary reason is to prevent the cutting surface from glazing or loading-up. If tool loading occurs, the material that’s being finished gets transferred onto the abrasive globules. That can degrade the Flex-Hone® tools soft, cutting action. By using a lubricant, however, fresh abrasive cutting particles are exposed continuously.   

Which Lubricant Should You Choose?

Flex-Hone® tools work well with many types of cutting fluids and coolants. Still, it’s important to consider the type of equipment that’s being used. In machining centers, flexible hones are often used with water-soluble fluids for maximum efficiency. Honing oils are commonly used when rigid honing equipment is modified for flexible honing operations. For finishing operations with handheld power tools, 10-30 weight motor oil, brake fluid, and hydraulic fluid all work well. 

Application requirements also affect lubrication selection. With sensitive electronics and medical components, traditional cutting fluids can’t be used. That’s why Flex-Hone® operators use warm water and liquid detergent instead. For all applications, avoid using highly chlorinated solvents. These fluids can degrade the epoxy matrix that contain a flexible hone’s cutting globules. 

In general, choose oil-based cutting and honing fluids for super-fine finishes. Water-based solutions are a good choice for general finishing and deburring applications. After flexible honing is complete, clean the cylinder properly to remove any residual particles or debris.   

What’s the Right Way to Use Lubrication? 

Before using the Flex-Hone®, thoroughly wet both the tool and the workpiece. Consider the type of finish that’s required, as well as the equipment or machinery that will be used. To avoid unnecessary wear on machine tool components, proper lubricant filtration is important whenever an abrasive tool is used in automated equipment. If you’re using the Flex-Hone® manually with a drill motor, coat the tool and the part before flexible honing begins. 

With automated machinery, flood coolant is commonly used. If an extra-fine finish is required, the flood of coolant washes away spent abrasive particles. This cleans the surface and reduces scratching. If a more aggressive finish is required, the flood of coolants may be turned-off during the honing cycle. This allows spent abrasive particles to remain at the cutting point and continue to support the finishing process.  

Why Use Flex-Hone® Oil? 

Flexible honing supports the use of many cutting fluids and honing oils, but BRM Flex-Hone® Oil has been specially-formulated for use with all abrasive types and on all types of metal. Along with its special blend of honing and lapping oils, Flex-Hone® Oil contains a lard to prevent galling of aluminum, a moisture dispersant, a non-ionic surfactant wetting agent to assure complete lubrication of the surface, and a special additive to help keep metal cuttings and contaminants in suspension. Flex-Hone® Oil also includes an emulsified anti-bacterial agent.   

Flex-Hone® oil is engineering to maximize the benefits of flexible honing and to promote tool life, a superior surface finish, improved cutting action, and shorter cycle times. For more information about flexible honing, download the Flex-Hone® Resource Guide.