Application Deep-Dive
API 6A Machining Processes — Documentation, Tolerances, and Quality Practice
API 6A (Wellhead and Christmas Tree Equipment) sets the standard for wellhead component manufacturing. Whether the finished part carries the API monogram or is API 6A-adjacent, the tolerance discipline and documentation practice matter. This guide covers what buyers specifying API 6A machining should expect from a supplier.
What API 6A specifies
API 6A defines dimensional and quality requirements for wellhead and Christmas tree equipment: bodies, adapters, spools, valves, chokes, and related hardware. Pressure ratings from 2K to 20K psi; material grades from Class AA (standard service) to Class HH (severe sour service).
The spec covers materials, dimensions (especially ring gasket grooves and flange geometry), NDE (non-destructive examination) requirements, and Product Specification Levels (PSL 1–4) which define QA rigor.
Ring gasket grooves — the API dimensional practice
API 6A ring-groove dimensions (BX-series, R-series) are precisely defined in the spec. Machining must hold groove diameters, angles, and surface finishes to the spec. Tolerance callouts on the groove are what determine sealing performance under pressure cycling.
Typical: ring groove diameter ±0.005", groove angle per BX or R spec, surface finish 63 μin Ra maximum, with cleanliness (no burrs, no tool marks in the sealing direction).
Material specifications
| Material class | Alloys typically used | Service |
|---|---|---|
| Class AA-BB (standard/sour) | 4130, 4140, F22, F91 | Standard oilfield service |
| Class CC-DD (higher-sour) | Inconel 718, Super Duplex 2507, 17-4 PH | H2S sour service |
| Class EE-FF-HH (severe sour) | Inconel 625, 718, K-500 | Severe H2S or chloride service |
| Class TT (temperature) | Alloys per operating temperature range | High-temperature applications |
Documentation and PSL levels
PSL 1: baseline manufacturer inspection and documentation. PSL 2: adds specific NDE (magnetic-particle, dye-penetrant, hardness). PSL 3: adds material property verification (chemistry, mechanical testing, third-party witness). PSL 4: highest rigor for extreme service.
Machining shops should know what PSL the finished part must meet and produce the documentation trail accordingly.
What B&R Productions delivers on API 6A-adjacent work
Material traceability by heat and lot on every job. First-article CMM inspection standard. API 6A-adjacent tolerance discipline on ring grooves, flange faces, and bore geometry. Certificate of conformance with delivery. Support for customer-specific PSL requirements and ITPs.
Coordination with heat-treat and NDE vendors for full-package delivery when required.
Frequently asked questions
Where can I get API 6A wellhead components CNC machined in Texas?
B&R Productions in New Waverly, TX machines API 6A wellhead components regularly. Direct number for RFQs and rig-down work: (936) 291-7827.
How long does API 6A wellhead components machining typically take?
Depends on quantity and material availability. Standard work: 1–3 weeks. Emergency turnaround: same-day to 3 days when material is on the shelf. Call to discuss your specific job.
What's the difference between API 6A and API 6D?
API 6A covers wellhead and Christmas tree equipment (at the wellhead itself). API 6D covers pipeline valves (downstream). Different dimensional specs; similar material and quality principles.
What material classes are commonly requested for API 6A machining?
Class BB and CC are most common for standard sour service (4140, F22, 17-4 PH). Class DD-EE-FF for higher-sour or extended-service applications (Inconel 718, 625, 2507).
Do all API 6A parts require full PSL 3 or 4 documentation?
No — PSL requirement depends on the specific application and buyer specification. PSL 1 or 2 is common for standard-service parts; higher PSL for critical or high-consequence-of-failure parts.
Does B&R Productions carry an API 6A monogram license?
Contact us for current API monogram licensing status. We machine to API 6A-adjacent tolerance and documentation practice routinely; whether the finished part carries the API stamp depends on the specific licensing arrangement.