Vacuum Chamber Components — A Leak You Cannot Find Is Usually a Hole You Cannot Clean
Four defects that pass inspection and fail pump-down
- Virtual leak from a trapped cavity. A blind hole, an unvented screw pocket or a closed internal passage holds air and cleaning fluid. It releases slowly under vacuum and behaves exactly like a real leak without being one.
- Seal-groove surface damage. A scratch, a chatter mark or a witness line running across an O-ring groove gives the elastomer a path around itself. The groove can be dimensionally perfect and still not seal.
- Interfacial burr on a flange face. A knife-edge or metal-to-metal seal depends on the faces meeting. A burr at the bolt-hole exit or along the face edge holds them apart by an amount that no torque will close.
- Smeared surface before coating. A burnished wall closes surface porosity and then opens it during cleaning or bake-out. Plating and anodising also reject a smeared substrate, which turns a machining issue into a coating scrap.
If the part carries pressure rather than vacuum, with a moving element inside the bore, the failure logic is different — see Hydraulic Valve Body Machining.
What drives tooling on a chamber part
| Feature | What usually decides the tool | HENTRY entry |
|---|---|---|
| Flange and chamber faces | Whether the limit is smearing on aluminum or geometry on stainless | PCD Milling Cutter · Shell Mill |
| O-ring and knife-edge grooves | Cutting the form in one pass so no witness line crosses the seal path | Grooving Tools · Custom End Mills |
| Gas passages and cross-drilled ports | Depth, whether the passage vents, and the sequence that lets chips leave | Through-Coolant Carbide Drills |
| Blind tapped holes | Whether the print allows a vent, a through hole, or a defined flat bottom | Spiral Flute Taps · Flat Bottom Carbide Drill |
| Viewport and feedthrough seats | Roundness and face flatness together, because the seal sees both | Fine Boring Tools · Carbide Reamer |
Which alloy pushes you where
| Material | Route | Why |
|---|---|---|
| 6061-T6 plate | PCD for faces and grooves, carbide for holes | Clean shear and long tool life; residual stress in the plate is the bigger risk than the cut |
| 5083 aluminum | PCD, with attention to built-up edge | Softer and gummier than 6061; a dull edge smears instead of cutting |
| 316L stainless | Carbide throughout, sharp edge, no dwelling | Work hardening; a rubbing pass hardens the surface and the next cut tears it |
| Aluminum-silicon-carbide | PCD only, with a geometry that shears the particle phase | Highly abrasive; carbide life is short and the failure is chipping rather than wear |
| Ceramic, quartz, graphite | Not from this page | These fail by chipping and fracture; the process chain is different and is reviewed separately |
Boundaries, so you do not read the wrong page
- Wafer-contact surfaces, chucks and end effectors — flatness and particle generation → Wafer Handling Component Machining.
- Micro-channel cold plates — fin geometry and brazing faces → Semiconductor Cooling Plate Machining.
- Pressure-tight bores with a moving spool → Hydraulic Valve Body Machining.
- Deep intersecting oil galleries on a hydraulic block → Hydraulic Manifold Drilling.
What makes a chamber-part quote reviewable
- Which faces see vacuum, which see atmosphere, and which are the seal interfaces
- Leak-rate requirement and the test method — helium spray, rate-of-rise, or both
- Groove detail: form, depth, width and the surface callout that matters to the seal
- Whether blind holes can be vented or converted to through holes
- Downstream finish — anodise, plate, passivate — and the surface expectation behind it
- Material, temper and whether the stock is stress-relieved before machining
Quick answers before you RFQ
Can a machining change remove a virtual leak?
Sometimes, and it is the cheapest place to look first. If the trapped volume is a blind hole bottom or a chip pocket, changing the drill geometry, adding a vent or re-sequencing the operation removes the reservoir entirely. If the volume is inside an assembly — behind an insert or a welded plate — machining cannot reach it and the fix has to be in the design.
Why does a groove need to be cut in one pass?
Because a second pass starts somewhere on the first surface and leaves a transition. On a flat face that is cosmetic; across an O-ring groove it is a potential leak path. Where a groove cannot be cut in one pass, the entry and exit of the second pass are positioned deliberately rather than left where the tool happens to start.
Is PCD necessary for every aluminum chamber part?
No. It is the right choice where smearing, built-up edge or life is the limit. On a one-off chamber body with deep pockets and thin walls, carbide geometry usually matters more than PCD, and adding PCD does not fix a deflection problem.
Do you handle the coating as well?
No. We machine to the surface condition the coating needs and quote the tooling for it. The anodising, plating or passivation step and its acceptance stay with the supplier who owns that process, and we ask for their expectation up front so the two do not disagree after the parts are made.
Send the print with the vacuum side and the seal faces marked
Primary tooling entries for chamber parts: PCD milling cutters, grooving geometry for seal forms, through-coolant drills and fine boring tools for viewport seats. Blind holes are reviewed as a trapped-volume question, not only as a drilling question.