Kovar 4J29 & Vacuum Sealing Components, Sliding-Head Turned

Kovar is the alloy instrument and vacuum equipment makers struggle to source machined: matched thermal expansion for glass and ceramic seals, and almost no shops keep it running. We sliding-head turn Kovar 4J29 sealing housings, feedthrough parts and sensor housings from 100 pieces, quoted in 48 hours with EN 10204 3.1 certificates and samples in 7–15 days. Pilot batches start at 100 pieces.

Why Kovar parts are hard to source

Kovar 4J29 exists for one reason: its thermal expansion matches glass and ceramics, which makes it the alloy behind hermetic feedthroughs, sensor housings and seal assemblies in instruments and vacuum systems. The same property makes it unforgiving to machine, so few job shops keep tooling and process knowledge for it, and buyers routinely wait weeks for parts that take hours to turn once the process is proven. The buying pattern is therefore small, urgent and quality-critical: 100 to 500 pieces for a sealing trial, ordered against a delivery date that the whole program is waiting on.

We keep Kovar 4J29 as a running material on sliding-head lathes, with tooling, speeds and deburring routines proven on sealing housings, feedthrough components and sensor bodies. Parts ship with EN 10204 3.1 certificates and a dimensional report, first articles take 7 to 15 days, and DDP deliveries arrive in 5 to 8 days by air — so your sealing partner assembles from stock instead of waiting for a mill order and a machining slot. Pilot quantities ship on the same process and documentation as series, so approval results stay valid at volume.

Typical component families and processes

Degassing and nickel plating through audited partners, documented with the batch; small pilot batches welcome.

Workflow: drawing, sample approval and recurring series

The standard flow: drawing review and quotation within 48 hours, first samples in 7–15 days, first article inspection and approval, then series production against the approved reference. Tooling, program revisions and inspection records are kept on file so that call-offs remain consistent with the approved first article.

Engineering changes — material substitutions, tolerance updates, plating or packaging changes — are handled as controlled changes against the same records.

Quality and documentation

DIN ISO 2768-mK applies as the default tolerance scheme for unspecified dimensions. EN 10204 3.1 inspection certificates are standard for metallic parts, First Article Inspection supports the approval step, and RoHS/REACH declarations are available where required. Plating, cleanliness and packaging requirements are confirmed per drawing.

FAQ

Why Kovar 4J29 and not a substitute?
Where a housing is sealed to glass or ceramic, expansion matching is the whole point of the alloy: substitutes crack the seal on thermal cycling. We machine certified 4J29 with mill certificates per batch, keep dedicated tooling so surface quality stays consistent, and supply the dimensional report your sealing partner needs to set up the brazing or welding run.

What batch sizes make sense?
From 100 pieces per item. Because the alloy is stocked and the process is proven, small pilot batches are economical for design validation, and pricing steps down sharply at 500 and 2,000 pieces. Most programs start with 100 to 300 machined housings for seal trials, then move to annual call-offs against a stored specification and tooling.

Can you match our glass or ceramic supplier?
Yes. We machine to the expansion-matched dimensions your seal design requires, report the critical diameters individually, and coordinate delivery timing so housings arrive before your sealing run. Where plating or degassing is needed before sealing, our partners process and document it as part of the same batch record, so nothing arrives undocumented. Sealing trials typically run on 100 to 300 housings, delivered together so the whole trial uses one certified melt.

How is quality controlled on this alloy?
Dimensional reports cover the sealing diameters and critical features with actual measured values, surfaces are protected from handling marks through the whole process, and material certificates trace every batch to the certified melt. Because Kovar parts usually end up inside sealed assemblies, we treat the documentation with the same care as the machining itself. Dimensional reports list actual measured values on every sealing diameter, not typical values. Typical turnaround from sample receipt to reported dimensions is 7 working days.