NXF UNS S30400 ASTM 304/JIS 304/EN 1.430 DN6-1200 Class3000-9000 Stainless Steel 304 Forged Fitting Threaded Cross

1. Raw Material Inspection and Cutting

The production of threaded couplings starts with raw material verification. Factory inspectors check the material grade, hardness, surface smoothness and dimensional tolerance of the raw round bar or pipe materials to ensure they conform to production standards. Materials with cracks, rust, deformation or uneven hardness are eliminated. Qualified blanks are cut into fixed lengths according to processing drawings, with flat and vertical cutting end faces to guarantee consistent size of each coupling workpiece.

2. Preliminary Turning and Shaping

After cutting, the workpieces are sent to CNC lathes for preliminary machining. This process includes outer diameter trimming, inner hole boring and end face finishing. Operators precisely control the outer circle size, wall thickness and workpiece straightness to ensure the overall dimension of the blank meets the standard range. All burrs and sharp edges generated during cutting and turning are completely removed to prepare for accurate thread processing.

3. Precision Thread Machining

Thread processing is the core procedure of coupling production. According to standard metric or British thread specifications, professional thread rolling or thread turning equipment is used to machine internal or external threads. The equipment strictly controls thread pitch, tooth depth and tooth profile angle to ensure uniform and neat thread shape without broken teeth, rough surfaces or dimensional deviation. High-precision thread processing guarantees smooth assembly and tight meshing with matching pipes and rods.

4. Groove and Sealing Structure Processing

For sealed threaded couplings, secondary precision machining is carried out for auxiliary structures. This step processes sealing grooves, gasket positioning steps and anti-loosening structures on the coupling body. The size and depth of the sealing groove are precisely controlled to ensure perfect fit with rubber gaskets or sealing rings. This procedure effectively improves the air tightness and pressure resistance of the finished coupling, avoiding medium leakage during pipeline operation.

5. Surface Treatment and Anti-corrosion Processing

After mechanical machining, all threaded couplings undergo professional surface treatment. Common processes include polishing, deburring, oil removal and cleaning.  while stainless steel couplings adopt fine polishing and passivation treatment. Surface processing can improve the appearance quality, enhance wear resistance and extend the service life of threaded couplings.

6. Finished Product Inspection and Packaging

All finished couplings need comprehensive quality inspection before delivery. Workers use professional thread gauges, calipers and pressure testing equipment to detect thread accuracy, dimensional tolerance, sealing performance and structural stability. Appearance inspection is carried out to screen out products with surface defects. Qualified products are cleaned and dried, then classified and packaged according to specifications. Unqualified workpieces will be reworked or scrapped to ensure overall product quality.