About This Part
A hydraulic housing is the body of a valve, manifold or cylinder that contains pressurized fluid. In hydraulic valve body machining, every internal passage, seal land and port must be leak-tight at operating pressure — which means no porosity connecting passages, no burrs that can break free and contaminate downstream components, and sealing surfaces that sit flat under bolt load. This is leak tight cnc parts work: a housing that seeps or fails under pressure is a safety issue, not just a cosmetic reject, and a dislodged burr that migrates into a valve spool can seize an actuator mid-cycle. This pressure rated machining project uses **Stainless Steel 316**, chosen over 304 for its superior corrosion resistance to hydraulic fluids, saltwater and outdoor environments, as well as its higher molybdenum content for pitting resistance in wet service. The housing is produced entirely by **5-axis CNC milling**, which allows internal passages, spool bores, port connections and mounting faces to be machined with minimal setups. All critical features — bore diameters, sealing-groove geometry and cross-passage positions — are held to **±0.005 mm on critical dimensions**. In stainless steel 316 cnc housing work, tool wear and heat management define whether a part is done right or done twice; 316 is significantly harder to machine cleanly than aluminum or mild steel, and errors compound fast.
**Part:** Hydraulic Housing
**Process:** 5-axis CNC milling
**Material:** Stainless Steel 316
**Tolerance:** ±0.005 mm on critical dimensions
**Inspection:** 100% CMM verification, full report with shipment
Challenges of This Part & How We Machined It
Cross-drilled passage intersections without hidden burrs
Hydraulic housings carry fluid through a network of intersecting drilled passages. Where two passages meet, the drill that breaks through into an existing hole leaves a ragged burr at the intersection. If that burr is not removed, it either stays in place (creating turbulence and a stress riser that can fatigue-crack under cyclic pressure) or breaks loose in service and lodges in a valve spool — causing a failure that is difficult to diagnose and dangerous in operation. Removing these burrs is non-trivial because the intersection is deep inside the part, inaccessible to hand tools. We use dedicated cross-hole deburring tools that reach through drilled passages to remove intersection burrs, and we flush every passage with high-pressure fluid to clear chips. Ports are inspected with a borescope before sign-off.
Tool wear and heat in Stainless 316
Stainless 316 is more difficult to machine than 304. It work-hardens under poor cutting conditions, generates significant heat at the tool edge, and wears end mills and drills faster than mild steel or aluminum. When a tool wears mid-run, bore diameters drift, surface finish degrades, and tap breakage in deep holes becomes a real risk — a broken tap in a near-finished hydraulic housing is often a scrap part. We use carbide tooling with coatings selected specifically for stainless, monitor tool life based on cut time rather than waiting for a failure or a visible wear line, and direct high-pressure coolant to the cutting edge to keep temperatures down and evacuate chips from deep pockets. Dimensional consistency holds across the production run, not just on the first part.
O-ring groove geometry and sealing face flatness
A hydraulic seal is only as good as the groove it sits in and the face it seals against. O-ring grooves must be held to precise width and depth (too deep and the ring does not compress enough to seal; too shallow and it gets pinched and fails under pressure cycling), the groove surface must be free of spiral tool marks that create leak paths, and the bolted face must be flat enough to compress the seal evenly around the full perimeter. We finish O-ring grooves with form tools programmed to the exact groove geometry, take light final passes on the sealing face after all heavy milling is done, and verify groove dimensions on the optical comparator or with silicone cast impressions that capture the full profile.
Machining Sequence
1. **CAM programming with passage verification** — internal fluid passages are modeled and drill paths verified to ensure correct intersection geometry and adequate wall thickness between adjacent passages (no cross-talk).
2. **5-axis rough milling** — heavy stock removal from the 316 billet, with carbide tooling at parameters tuned to control heat and minimize work hardening.
3. **5-axis finish milling and boring** — spool bores, port seats, mounting faces and O-ring grooves are finished in coordinated setups to preserve alignment between fluid passages and bolt patterns.
4. **Cross-hole deburring and flushing** — all internal passage intersections are deburred; the housing is flushed with high-pressure fluid to remove all chips, then blown clean with filtered air.
5. **CMM inspection and pressure testing** — bore diameters, groove geometry and port positions are verified; pressure testing can be performed per customer specification before shipment.
What You Get With Every Order
- **Free DFM review before quoting** — we flag manufacturability risk early, not after parts are made - **First Article Inspection report** with the first batch - **CMM dimensional report** on critical features - **Material certificates** for aerospace and medical grades - **Direct communication with the shop** — no trading company in between, we make the parts ourselves
Have a Drawing?
Send us your drawing or STEP file and we will come back with pricing within 48 hours. Prototype quantities and production runs both welcome — no minimum order quantity.
**TruPart Precision** trupartprecision.com | sales@trupartprecision.com WhatsApp: +86 137 1278 3205 No.114 Xinhua Road, Xinhe Dev Zone, Wanjiang, Dongguan, China