Nagel EC Series

Honing is a precision abrasive finishing process that uses a rotating, reciprocating multi-stone tool to remove small amounts of material (typically 0.02–0.2 mm) from a bore surface. Unlike grinding (which uses a single wheel), honing uses multiple abrasive stones arranged around a self-centering body, and unlike boring (which cuts with a single point), honing removes material across the full bore circumference simultaneously. Honing corrects cylindricity, roundness, and produces the controlled cross-hatch surface texture — a combination of grooves at opposing helix angles — that is critical for oil retention in engine cylinder bores and sealing in hydraulic components.

The cross-hatch angle is the angle between the honing grooves and the bore axis, produced by the ratio of spindle rotation speed to stroke reciprocation rate. Engine cylinder bore specifications typically require a cross-hatch angle of 40–60 degrees included angle. This specific geometry creates a surface that retains oil during the piston downstroke while wiping excess oil during the upstroke — essential for proper lubrication without excessive oil consumption. The Nagel EC series controls cross-hatch angle precisely by CNC management of spindle RPM and stroke rate. Hydraulic bores require different cross-hatch specifications optimized for sealing performance.

Aluminum engine block cylinder bores are honed with CBN (cubic boron nitride) superabrasive stones or with aluminum oxide stones depending on the process stage. Plateau honing (the final finish step used for most OEM engine production) uses a sequence of abrasives: first a coarser stone to establish the cross-hatch geometry and remove stock, then a finer stone or CBN plateau hone to remove the peaks of the cross-hatch while leaving the valleys intact for oil retention. The Nagel EC series tooling is compatible with both conventional and CBN abrasive specifications.

Air gauging is a non-contact precision measurement technique that measures bore diameter by measuring the air flow (or back pressure) through a precision nozzle inserted into the bore. The measured air pressure is directly proportional to the clearance between the nozzle and bore wall — bore diameter is calculated from this measurement with resolution to 0.0001 mm (0.1 µm). In the Nagel EC series, the air gauge is integrated into the honing tool, measuring bore diameter during the honing process and feeding back to the CNC to control expansion force and stop honing when the target diameter is reached — eliminating manual gauging and enabling fully automatic size control.

Multi-stroke honing (used in the Nagel EC series) reciprocates the honing tool through the full bore length many times, progressively removing material until the target diameter and finish are reached. This is the standard process for most engine cylinder and hydraulic bore honing. Single-pass honing (used in different Nagel machines) passes a series of expanding abrasive tools through the bore in one direction only — used in high-volume production where cycle time must be minimized and bore geometry is already close to final size. Multi-stroke honing corrects more geometry error and achieves finer finish; single-pass honing is faster but requires tighter pre-machining control.