🛡 VALVE BLOCKS · CROSSING GALLERIES

Valve Block & Manifold Drilling

A valve block is a block of metal full of drilled galleries that cross and merge to route hydraulic fluid. The crossings are drilled blind from both ends, gundrilled on a machining center, then the whole block is burr-controlled and pressure-tested. The geometry is simple; the cleanliness requirements are not.

Ø6–25 mmgalleriesTypical bore sizes

Blind + crossinggeometryDrilled from both ends

±0.1 mmpositionCrossing tolerance

500 bar+testPressure integrity

PRINCIPLE

How Valve Blocks Are Drilled

A valve block's galleries are straight blind holes drilled from the faces, arranged so they intersect inside to form the circuit. Each passage is drilled from the face it belongs to, often from both ends meeting mid-block. Because the holes cross, a small entry error can make two galleries miss each other entirely — the crossing tolerance drives everything.

💡 Method: most valve blocks are gundrilled on a machining center or VMC with through-spindle coolant. The galleries are short enough (10–40×D) that a machining center gundrill handles them, and one setup drills all faces.

CROSSINGS

The Crossing Gallery Problem

When two blind galleries cross, three things matter:

Intersection: each hole must land inside the other’s diameter. Hold entry position to ±0.1 mm and drill straight — wander at 20×D eats the whole margin.
Chip traps: the last hole drilled dumps chips into the first gallery. Flush aggressively and, on critical blocks, use a burr brush or abrasive flow.
Burr at the crossing: the drill exit into an existing gallery raises a burr that can break loose in service. Deburr every internal exit — a wire brush pull-through or an EDM deburr pass on fine blocks.

⚠️ Drill order matters: drill the shortest, straightest passages last so their chip stream has a path out. On blocks with many crossings, a drilling sequence plan is part of the process design, not an afterthought.

PARAMETERS

Starting Parameters

Material	Vc (m/min)	Feed @ Ø10 (mm/rev)	Coolant
Cast iron (GG25)	60–100	0.02–0.05	Emulsion / oil
Aluminum (6061)	80–160	0.03–0.08	Emulsion / synthetic
Ductile iron	50–80	0.02–0.05	Emulsion
Steel (4140)	50–80	0.02–0.04	Oil / emulsion

✅ Machining center practice: with through-spindle coolant at 50–150 bar and a bushing plate or drill guide, a VMC holds the position and straightness valve blocks need — no dedicated gundrill machine required until volume or length grows.

BURR & CLEANING

Burr Control & Cleaning

Entry burrs: controlled by spot-facing or chamfering before gundrilling.
Internal crossings: pull-through burr brushes sized to each gallery, or an abrasive-flow pass on high-performance blocks.
Chip removal: high-pressure flushing with clean fluid, then a hot rinse; some specs add an ultrasonic clean.
Verification: pressure test to 1.5× working pressure and leak-check every block — a loose chip that jams a spool is a field failure.

PROS & CONS

Drilling Approach Trade-offs

✅ Gundrill on VMC

One setup drills all faces
No dedicated machine needed
Good straightness for short galleries

⚠️ Watch out

Long galleries > 40×D wander on a VMC
Chip management at crossings needs process discipline
Blind-end burrs need dedicated deburr steps

Valve Block & Manifold Drilling

How Valve Blocks Are Drilled

The Crossing Gallery Problem

Starting Parameters

Burr Control & Cleaning

Drilling Approach Trade-offs

✅ Gundrill on VMC

⚠️ Watch out

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