CNC Machined Stainless Steel Control Valve Body
Custom CNC machined stainless steel control valve bodies for hydraulic, pneumatic and process control. Cross galleries, spool bores and port threads are machined from a single datum, sealing faces are lapped flat to 0.005 mm, and every body is pressure tested before it ships.
- Lapped Sealing Faces
- Ports Gauged 100%
- Pressure Tested to 250 bar
- Passivated After Machining
*Send the spool drawing and the flow path, because the gallery diameter, the plug positions and the wall between cross-drilled holes all follow from the circuit.
Stainless Control Valve Body Overview
A valve body is a block of metal with a circuit cut into it. The circuit only works if the cross-drilled galleries meet exactly where the drawing says, because a 0.2 mm offset at a junction leaves a step that traps fluid and disturbs the flow.
The body is milled from a solid block, with the spool bore and the port faces machined from one datum so the spool does not bind. Cross holes are drilled with a spot face at each entry, and the sealing faces are lapped rather than milled, because a milled face leaves a tool mark that a soft seal cannot follow.
304L Stainless Steel Bar
304L is chosen for housings and fittings that see coolant, washdown or outdoor service. It welds without carbide precipitation, machines to a fine finish on the sealing faces, and needs no coating, so a scratch does not become a corrosion point.
17-4PH / 316L Stainless
17-4PH is specified when the housing has to hold a thread or a press fit under load. After ageing it reaches roughly 1,000 MPa and still machines to a fine bore. 316L is the alternative when chloride exposure is the concern and strength is secondary.
Material follows the fluid and the pressure. 304L covers water and air, 316L is used with aggressive media, and 17-4PH is chosen where the body also carries a high thread load or a spool bore under pressure.
Stainless Steel Control Valve Body Specifications
Machining and testing data for valve bodies, agreed against the circuit drawing and the working pressure.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Control Valve Body / Directional Valve Block | Machining Process | 4-Axis CNC Milling, CNC Turning |
| Material | 304L / 316L / 17-4PH Stainless Steel | Typical Tolerance | ±0.02 mm on Bore, ±0.05 mm on Port Centres |
| Body Size | 40 × 40 × 40 mm to 250 × 200 × 150 mm | Sealing Face Flatness | 0.005 mm, Lapped |
| Bore Diameter | 6 – 40 mm | Bore Roundness | 0.005 mm |
| Port Threads | BSPP, NPT, SAE, Metric, 1/8 to 1 inch | Thread Accuracy | 6H, Gauged 100% |
| Working Pressure | Up to 250 bar Depending on Section | Surface Finish | Ra 1.6 µm Internal Gallery, Ra 0.4 Seal Faces |
| Features | Cross Drilling, Plug Ports, Spool Bore, Mounting Holes | Drawing Format | STEP, STP, IGES, X_T, DWG, DXF, PDF |
| Customization | Port Layout, Spool Bore, Plug Type, Marking | Lead Time | 8 – 14 Days (Prototype), 18 – 28 Days (Batch) |
| Inspection | CMM Port Map, Air Gauge Bore, Pressure Decay Test | Packing | Capped Ports, Individually Boxed, Crate |
Key Features of Our CNC Machined Valve Bodies
A circuit that meets where the drawing says, and a seal face that a soft seal can follow.
Single-Datum Galleries
All cross holes and the spool bore are machined from one datum, so junctions meet without a step and the spool travels without binding.
Lapped Sealing Faces
Seal faces are lapped to 0.005 mm flatness and Ra 0.4, which is what lets a soft seal seat without lapping compound on site.
Gauged Port Threads
Every port thread is checked with a go/no-go gauge and its face is spot-faced square to the thread axis, so a fitting seals at the shoulder.
Pressure Decay Test
Bodies are capped and tested above working pressure before dispatch, and the decay record ships with the part.
Chasing an internal leak in a valve block?
Surface Finishes for CNC Machined Valve Bodies
On a valve body the internal finish governs contamination and the external finish governs corrosion.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| As Machined | Bare body where the fluid is compatible and the part is internal | Passivation | Removes free iron and restores the passive layer after machining |
| Electropolishing | Smooth gallery for low particle retention | Glass Beading | Uniform matte external face |
| Zinc Nickel Plating | External corrosion protection on carbon steel bodies | Masked Threads | Threads left bare so the coating does not change the fit |
*Electropolishing removes 5 to 10 µm from the gallery and the spool bore, which changes the clearance. The bore is left oversize by that amount when electropolishing is specified.
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CNC Machining Process for Stainless Valve Bodies
Cross-drilled galleries and the spool bore are cut from one datum, so the valve spools without binding.
01. Circuit Review
Read the circuit against the block size and check that every cross-drilled hole has enough wall to the next one, and that the spool bore clears the plug ports.
02. Block Preparation
Square the block on all six faces and face the datum face that every gallery and the spool bore will be referenced to.
03. Milling and Cross Drilling
Machine the port pads, the spool bore and the plug seats, then cross drill each gallery with a spot face at the entry to avoid a raised burr inside the bore.
04. Lapping and Passivation
Lap the sealing faces flat to 0.005 mm, deburr the galleries with a flexible hone, then passivate and cap every port.
05. Pressure Test and Inspection
Map the ports on a CMM, air-gauge the spool bore, pressure test above working pressure, and record the decay curve with the part.
Have a block that leaks internally or a spool that sticks? Send the circuit and the spool drawing, and we will quote the body that holds it.
CNC Machined Stainless Steel Valve Body FAQs
All galleries are programmed from one datum on the block, and each is drilled with a spot face at the entry. That removes the offset that normally appears when holes are drilled from two different faces.
A milled face carries a tool mark that a soft seal cannot follow, so it weeps. Lapping brings the face to 0.005 mm flat and Ra 0.4, which lets the seal seat on compression alone.
Up to 250 bar depending on the wall section between galleries and the port thread size. The wall is checked in the model before machining, and the body is tested above the rated pressure.
Yes, if you send the body or a full drawing with the port map. The replacement is programmed from the measured port positions rather than from a nominal drawing, which is what makes it drop in.
The body is supplied to the spool clearance you specify. Spools and seal kits can be sourced and fitted as an assembly if the valve is supplied complete.
Eight to fourteen days for a single body including machining, lapping, passivation and pressure testing. Batches of 20 or more run eighteen to twenty-eight days depending on the number of cross holes.
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