Honing - The Hole Story
Honing – The Hole Story
Making holes is one of the most common tasks in modern workshops – but how do you achieve high degrees of accuracy and surface finish? For many companies, the answer is simple: HONING.
The Evolution of Honing
The honing process has ancient origins, but advancements in techniques and abrasive technology have transformed it into a fast, efficient, and cost-effective method for precision bore finishing. Today, honing often surpasses internal grinding in both performance and affordability, producing components with exceptional accuracy. It is widely used across virtually all engineering sectors, handling production volumes from one-off prototypes to mass manufacturing runs. Honing is compatible with most metals and even non-metallic engineering materials.
Honing vs. Internal Grinding
Honing is frequently compared to internal grinding because both processes aim to achieve dimensional accuracy and superior surface finish. However, there are key differences:
Grinding uses an abrasive wheel moving at high speeds, imparting significant impact force along a line contact.
Honing involves a cutting medium carried by the honing tool, which is expanded, rotated, and reciprocated against the bore surface. The honing stones traverse in a helical motion, applying a shearing action at relatively low speeds and pressures compared to grinding.
The Honing Process
Honing is primarily used for finishing bores after drilling or reaming, but in some cases, parts can be honed directly from raw or sintered conditions. For example:
Tungsten carbide and ceramic components are often honed straight from sintered form.
Steel tubes may be honed directly from rolling mill conditions.
One unique aspect of honing is that either the tool or the workpiece must be fully floating, meaning it does not generate axial alignment or concentricity. Instead, honing maintains the alignment created by prior machining operations. For this reason, honing is often performed early in the manufacturing process to establish a datum location for subsequent machining steps.
Advantages of Honing
Compared to grinding, honing operates at much lower speeds:
Honing abrasives: 15-76 meters per minute
Grinding wheels: 762-2900 meters per minute
This lower speed offers several benefits:
Lower Equipment Costs – Honing machines do not require heavy-duty castings or specialized bearing systems, making them more affordable.
Reduced Heat Generation – Since the honing stones remain in constant contact with the surface, heat dissipates quickly, preventing workpiece damage.
Flexibility & Precision – The honing process allows control over multiple parameters, including rotation speed, reciprocation speed, stone pressure, honing fluid, abrasive type, grit size, and bond hardness.
Capability to Handle Challenging Bores – Honing easily corrects out-of-round, tapered, or bowed bores, as well as bores with keyways, ports, or dissimilar materials. Additionally, honing before heat treatment minimizes distortion.
Honing Capabilities & Equipment
Honing is suitable for a wide range of bore sizes:
Diameters: ∆1.0mm to over 1000mm
Lengths: Up to 10 meters or more
A variety of honing machines exist to accommodate these ranges, from manually operated units to fully automated honing systems with in-process size control for high-speed production.
Abrasives & Superabrasives
Honing stones are made from aluminum oxide or silicon carbide abrasive grits bonded together and cut to the required size. The choice of grit size and bond hardness determines the final surface finish. Recent advancements in superabrasives, such as diamond and cubic boron nitride (CBN), have revolutionized honing. These materials enable high-speed, precision honing with minimal operator involvement, making the process even more efficient and cost-effective.
The Future of Honing
Honing is a versatile process that can be applied to a vast range of materials, from copper to carbide, graphite to glass, powdered metals to polycarbonates. With ongoing technological advancements, honing continues to be a critical, economical, and precise solution for bore finishing in modern engineering.
Whether you need a high-precision finish for aerospace components or an efficient bore sizing solution for automotive parts, honing remains the hole story!