About This Part
A vacuum flange is the connection point where two sections of a vacuum system meet — and it is the place where leaks most often start. In KF flange cnc and ConFlat style applications, a tiny scratch, a slightly rounded knife edge, or a bolt-hole pattern that pulls the flange off-center will prevent a seal from forming at ultra-high vacuum levels. A cnc vacuum fitting that does not seal is useless regardless of how good every other dimension is. Flanges look like simple parts — a ring with holes — but the geometric demands are higher than almost any other turned component because every sealing defect is amplified by the pressure differential across the joint. This aluminum 6061 flange is produced by **CNC turning + milling**. The bore, seal geometry and flange face are turned in the lathe, while bolt holes and any side ports or rotation-lock features are milled secondaries. Critical dimensions — knife-edge geometry, bore diameter, face flatness and bolt-hole circle position — are held to **±0.005 mm on critical dimensions**. For semiconductor and research vacuum systems that run into UHV ranges, conflat flange machining demands a level of geometric perfection that general-purpose shops consistently miss; a nicked knife edge or a cross-hole burr can cost days of pump-down and troubleshooting.
**Part:** Vacuum Flange Fitting
**Process:** CNC turning + milling
**Material:** Aluminum 6061
**Tolerance:** ±0.005 mm on critical dimensions
**Inspection:** 100% CMM verification, full report with shipment
Challenges of This Part & How We Machined It
Knife-edge and seal-groove geometry
The sealing element of a CF or metal-gasket flange is a raised knife edge that must bite into a copper gasket to form the seal. The edge has a defined angle, height, and flatness band — too blunt and it does not deform the gasket; too sharp and it collapses unevenly when bolts are torqued; any nick or chatter mark across the edge becomes a leak path that is impossible to find once the system is assembled. We turn the seal geometry with a dedicated insert ground for the exact profile, run a single continuous finish pass with no dwell (which would leave a witness mark), and protect the finished edge from contact with any other part or tool during handling. The knife edge comes off the lathe clean, concentric and undamaged.
Bolt-hole circle concentricity to the bore
A flange that bolts together with the bore offset by 0.05 mm puts uneven crush on the gasket and will often leak along the lightly loaded side. Worse, if the bolt holes themselves are off-position, the assembly technician may be tempted to force the bolts, which can cock the flange and create a leak even on a perfectly machined sealing face. We mill the bolt-hole circle in a setup that references the turned bore as the datum rather than indicating off the chucked OD, which eliminates the stack-up error between lathe and mill operations. Bolt-hole position is verified on the CMM relative to the bore center, not just to the outer edge of the flange.
Burr-free internal bores and cross-drilled ports
A burr inside a vacuum passage is a virtual leak: gas trapped behind it releases slowly under vacuum, causing pump-down times to stretch or base pressure to never reach spec. Cross-drilled port intersections are especially prone to hidden burrs that are invisible from outside and difficult to remove by hand. We deburr every internal intersection with specialized cross-hole deburring tools, flush bores with high-pressure coolant to dislodge chips, and inspect internal passages with a borescope when geometry allows. The fitting ships clean, with no loose chips or hidden burrs waiting to cause pump-down problems.
Machining Sequence
1. **CAM programming with seal geometry profile** — turning and milling toolpaths are programmed around the bore as the primary datum; seal profile inserts are selected and verified under magnification before any cut is made.
2. **CNC turning of flange profile** — bore, flange face, knife-edge/groove and OD are turned in one setup to preserve concentricity between sealing surfaces and bore.
3. **CNC milling of bolt holes and ports** — bolt circles and any side ports are milled with the part located off the finished bore to maintain concentricity.
4. **Deburring and cleaning** — internal cross-holes are deburred; ultrasonic cleaning removes all coolant and particulate before the flange is sealed in a clean bag.
5. **CMM and visual inspection** — bore diameter, bolt-circle position, seal-groove profile and face flatness are verified; the knife edge is inspected under magnification before sign-off.
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