Technical insight
Vacuum Component Blind Holes: A Trapped-Volume Drawing Review
Before requesting a quote for a vacuum housing, spacer or internal support, identify which blind holes will be exposed to vacuum after assembly. Use a marked section view to ask the design owner about trapped volumes; do not turn a general request for venting into permission to modify the part.
By Geetai Precision
- Published
- Updated
A virtual leak versus an external leak
Leybold distinguishes gas released from internal cavities, blind holes and joints from leakage through a separating barrier. Its leak-detection guide calls these internal gas releases apparent or virtual leaks. A cavity in the assembled geometry therefore deserves review even when the discussion has focused on external seals. [1]
Kurt J. Lesker identifies gas pockets beneath ordinary fastener threads as a concern inside vacuum chambers and describes vented hardware intended to address those pockets. That is a reason to examine the complete fastened joint, not to assume that a threaded-hole callout alone settles the issue. [2]
Start with the assembled feature map
For this purchasing review, consider the part together with its mating hardware. Mark vacuum-facing surfaces, the installed fastener position and any enclosed space. Keep the supplied drawing unchanged while recording questions. The following worksheet is an editorial discussion aid, not a vent design or a machining instruction.
| Review point | Question to resolve | Record to request |
|---|---|---|
| Blind tapped hole | Will the installed screw leave an enclosed space, and where could gas leave it? | Request a marked assembly section and the design owner's disposition. |
| Fastener and washer | Has the actual hardware configuration been included in the venting review? | Identify the approved hardware reference alongside the component drawing. |
| Recess or mating joint | Does the assembled interface create a pocket absent from the standalone model? | List the affected feature and any open engineering question. |
| Proposed change | Who may approve a different hole, passage or fastener? | Record the written approval and controlled revision before release. |
Keep design decisions separate from quotation
For procurement, separate three responses: manufacture to the current approved definition; quote an alternative subject to approval; or hold the affected feature pending clarification. Ask the supplier to identify which response applies. Do not accept a silent change hidden in a quotation note, and do not authorize drilling an extra passage from this article.
Treat this worksheet as an upstream review, not a diagnosis of a pump-down problem. If operating behavior is the concern, involve the equipment owner and define a separate investigation. Leybold discusses multiple gas-source and leakage mechanisms; the presence of a blind hole by itself does not identify the cause of a particular system problem. [1]
Close the review before order placement
Attach the marked feature map to the quotation clarification record. For each open item, name the person who can answer it, the document that will capture the answer and the point at which purchasing must stop if it remains unresolved. Keep any requested leak test in its own acceptance specification and ask the designated engineer to approve that separate specification.
Geetai coordinates drawing-led manufacturing through long-term partners without presenting partner facilities as Geetai-owned.
Frequently asked questions
Should every blind hole be changed to a through hole?
No universal change is proposed here. Ask the design owner to review the assembled pocket and any proposed escape path. Keep the approved definition in force until a documented change is released.
Related review paths
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References
- Fundamentals of Leak Detection — Types of leaks, page 6 — Leybold. Accessed 2026-09-24T04:16:07.247Z.
- Vented Hardware Overview — Kurt J. Lesker Company. Accessed 2026-09-24T04:16:07.247Z.