Answering 5 Honing FAQs with Modern Machine Shop


As one of the most common machining operations, holemaking presents manufacturers with plenty of options. Depending on bore diameter and surface finish tolerance, a shop might choose drilling, milling, electrical discharge machining (EDM) or a combination of those CNC machining processes and achieve quality results. For example, the hole created by a 0.5-inch drill might range from ±0.002 inch or be as much as 0.006-inch oversized, but a subsequent reaming operation can produce a smoother surface finish and a hole diameter within ±0.0002 inch. Reaming or boring milled holes can achieve similar results, while EDM is even more precise, producing a bore diameter within ±0.0005 inch.

However, there are good reasons to turn to honing for applications with the most stringent requirements for surface finish and precision. According to Sunnen, a manufacturer of honing equipment that provided the information for this article, EDMed holes typically require further processing to smooth surfaces. The process is relatively slow as well. Optimized milling processes followed by boring or reaming may produce high-quality results, but not always consistently. Honing achieves all three goals: That is, the process consistently and reliably achieves bore diameter tolerances of ±0.0002 inch or tighter with high-quality surface finishes.

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