Cylinder walls with a superior surface finish have a uniform series of cuts, grooves, valleys, or scratches in a crosshatch pattern.

As BRM’s downloadable Gold Booklet explains, this surface finish provides a bearing surface for piston rings and promotes oil retention. 

For manufacturers, machinists, metalworkers, and mechanics, the BRM Flex-Hone® is the tool of choice for cylinder surface finishing. Made in the USA by Brush Research Manufacturing (BRM), this flexible cylinder hone reduces raised areas or ridges to a uniform height while creating a uniform series of oil-retaining valleys. Importantly, Flex-Hone® tools can also impart a cross-hatch pattern with larger or smaller angles.

Stroke Rate

Flex-Hone® tools don’t require specific training or instruction, but users need to understand the basics of cross-hatch patterns. The angle at which cross-hatch lines intersect can vary, and is a function of stroke rate, which is the number of inches per minute (IPM) that are fed or stroked during cylinder honing operations.

This table shows the relationship between stroke rate and cross-hatch angle. For complete information about tool selection and operating parameters, download the Flex-Hone® Resource Guide. 

Tool Diameter

Tool diameter is also related to stroke rate and cross-hatch angle. As a rule, smaller-diameter Flex-Hone® tools require faster stroke rates to achieve the same cross-hatch angle as larger-diameter tools. Flex-Hone® tools are always used in an over-sized condition, which means that their tool diameter is slightly larger than the cylinder bore.

The following table explains the relationship between tool diameters, stroke, rates, and 45° cross-hatch angles.  

45° Cross-Hatch Angles

As BRM’s Gold Booklet explains, a proper 45° cross-hatch angle is considered to be ideal for several reasons:

• When cylinder walls have a 45° cross-hatch, the upward motion of the piston spreads the oil sideways (in both directions) and covers the entire wall.
• When these oil-retaining grooves are evenly-spaced, the pistons rings tend not to rotate or surge in the direction of the groove.

Would you like to learn more about cylinder honing and cross-hatch patterns? For more information, download this free technical publication from BRM. 

Then, for complete information about tool selection and use, get the Flex-Hone® Resource Guide. This free, full-color publication explains what you need to know about BRM's industry-leading tools for cylinder surface finishing and deburring.   

Happy honing!