A 95.5 mm long Ø30 mm GGG50 bore in a hydraulic valve block, interrupted by control edges, was machined directly on a vertical machining center using a three-stage DIAHON FDhone honing process.

The precision honing process uses three graded FDhone honing tools. After honing tool 3, surface roughness Rz = 1.344 µm was measured. Additional analyses with DIAHON DPMS 3.0 confirmed roundness < 1 µm. Selected final geometry measurements also show sub-micrometre roundness and cylindricity below 2 µm.

• Component: hydraulic valve block / control housing
• Material: GGG50, 170–230 HB
• Bore: Ø30 ±0.001 mm
• Bore length: 95.5 mm
• Bore type: through bore with interruptions / control edges
• Form tolerance: 0.002 mm
• Surface requirement: Rz = 1.5 µm
• Pre-machining: grinding, Ø29.965 mm
• Machine: MATEC vertical machining center
• Coolant: oil

OP1 - honing: DIAHON FDhone, K076.

OP2 - intermediate honing: DIAHON FDhone, K046.

OP3 - fine and finish honing: DIAHON FDhone, K015.

The three-stage FDhone honing process separates geometry correction from finishing, which is especially important for this interrupted control bore.

Surface after honing tool 3: Rz = 1.344 µm. This is below the specified Rz = 1.5 µm surface requirement.

DIAHON DPMS 3.0: Additional analyses showed roundness deviation < 3 µm.

Selected final OP3 geometry measurements: roundness = 0.680–0.687 µm; cylindricity = 1.334–1.733 µm; straightness = 1.018–1.421 µm.

The geometry values are individual results from process development, not statistical capability indices.

• When precision honing the interrupted Ø30 mm bore, geometry is not determined by the FDhone tool alone; workholding can significantly influence the longitudinal bore form.
• The combination of ±1 µm diameter tolerance, 95.5 mm bore length and control edges makes clamping and cylindricity central process factors.
• The three-stage DIAHON FDhone honing sequence K076 → K046 → K015 separates geometry correction from finishing.
• After honing tool 3, Rz = 1.344 µm was measured, meeting the Rz = 1.5 µm requirement.
• DIAHON DPMS 3.0 additionally confirmed roundness < 3 µm.

Can an interrupted Ø30 mm GGG50 bore in a hydraulic valve block be precision honed?
Yes. This application used a three-stage DIAHON FDhone honing process.

Which DIAHON technology was used?
FDhone in three honing operations using K076, K046 and K015.

What roughness was measured after finishing?
After honing tool 3, Rz = 1.344 µm was measured, below the specified Rz = 1.5 µm.

How was roundness additionally checked?
Analyses with DIAHON DPMS 3.0 showed roundness < 3 µm.

How important is workholding?
It is a major factor. Process development showed that fixture-induced constraint can influence the longitudinal bore form.

The project demonstrates that precision honing an interrupted Ø30 mm GGG50 bore in a hydraulic valve block is technically manageable with a three-stage DIAHON FDhone honing process. After honing tool 3, Rz = 1.344 µm was measured; additional DIAHON DPMS 3.0 analyses confirmed roundness < 3 µm.

The process development also shows that tool sequence, pre-machining, workholding and bore measurement must be treated as one system when honing tight dimensional and form tolerances.