Honing: What It Is, How It Works, and Key Applications in Precision Machining

Honing, alongside grinding and lapping, is one of the primary finishing processes used in most machine shops. Of the three, honing is often the most capable yet underutilized operation, offering precision and versatility in a variety of applications.

What is Honing?

Honing removes material from a workpiece through abrasion, utilizing tools embedded with abrasives like aluminum oxide, CBN, and diamond. These abrasives are typically formed into solid shapes, commonly referred to as “stones.” Unlike grinding, which operates at cutting speeds starting around 5,000 sfm (1,524 m/min), honing is performed at much lower speeds, starting at about 65 sfm (19.8 m/min).

Advantages of Honing Over Other Processes

• Material Removal Rates: Honing matches or exceeds the material removal rates of grinding for fine finishes.
• Precision: Honing is ideal for accurately removing small amounts of material with tolerances as tight as 0.0002″ (0.051 mm).
• Heat Management: Lower cutting speeds generate less heat, preventing damage to delicate parts like gear teeth.
• Portability: Honing tools can be used outside the shop with simple electric drill motors.

Engine reconditioned with a Sunnen CV-616 automatic cylinder hone. Image courtesy of Galloway Engine Reconditioning.

Applications of Honing

1. Cylinders and Hydraulic Components

Honing is synonymous with finishing cylindrical components, such as engine and hydraulic cylinders. This process imparts a crosshatched surface pattern, which effectively holds lubricant while preventing leaks under high pressure. For example, honing enables precision in hydraulic pumps operating at pressures up to 5,000 psi (345 bar).

2. Correcting Geometry Issues

Honing tools use long stones with significant engagement in the bore, allowing them to self-center and correct out-of-roundness or misaligned holes. This capability is particularly useful for deep bores with high length-to-diameter ratios, which can be challenging to machine with other processes. For more on energy-efficient machine tools, see this related guide.