The seat swivel base is the load path between a truck or bus seat and the cab floor. It carries the seat, the occupant, the seatbelt anchorage and — during a crash event or severe off-road impact — deceleration loads many times body weight. Ningbo Ruican casts these bases with controlled section thickness and full-radius fillets so stress flows through the part instead of concentrating at corners. The result is a swivel base that passes pull and fatigue testing without the weight and welding cost of a fabricated steel assembly.
Specifications
| Item | Detail |
|---|---|
| Casting process | Silica sol investment casting |
| Material options | Carbon steel 1020, 1025, 1045; low-alloy steel 4140, 4130; ductile iron EN-GJS-500-7 |
| Dimensional tolerance (ISO 8062-3 CT grade) | CT6–CT7 as cast, CT5 on bearing bore and mounting face |
| Machining | 4-axis VMC: mounting face milling, swivel bearing bore boring, bolt hole drilling and tapping, seatbelt anchor thread machining |
| Surface finish (Ra) | Ra 6.3 µm as cast; Ra 1.6–3.2 µm on machined mounting and bearing surfaces |
| Weight range | 2.2 kg – 9.0 kg |
| Typical lead time | Tooling 4–6 weeks; samples 5–7 weeks; production 4–6 weeks |
Key features
- Generous cast fillet radii at all section changes eliminate the sharp-corner stress risers typical of welded plate designs.
- Uniform wall thickness control prevents shrinkage porosity in high-stress areas of the base.
- Precision-bored swivel bearing race seat gives smooth rotation with no play after extended service.
- Machined mounting face held flat so the base seats squarely on the cab floor without shimming.
- Integrated seatbelt anchorage and stop-lug features cast in, reducing part count and assembly time.
- Optional heat treatment to 4140 quenched and tempered specification for high-load off-highway applications.
Applications
- Long-haul and regional distribution trucks
- City, coach and intercity bus driver seats
- Construction and mining off-highway machine cabs
- Agricultural tractor and combine harvester seats
- Municipal refuse truck and fire apparatus cabs
- Military and special-purpose vehicle seating systems
Quality & compliance
Seat swivel bases are safety-relevant components, so Ningbo Ruican applies full APQP discipline with process FMEA, control plan and PPAP submission at level 3 or 4. Every heat is certified with traceable mill documentation and mechanical test results, and magnetic particle or dye penetrant inspection is available on 100% of parts or to an agreed sampling plan. Dimensional reports cover bearing bore, mounting face flatness and seatbelt anchor thread integrity from CMM and gauge inspection. Fatigue cycling, static pull testing to your seat anchorage specification, and salt-spray testing to ASTM B117 can be arranged and documented.
FAQ
Can you meet seat anchorage strength and fatigue requirements?
Yes. We design the casting with the load paths your specification demands, control section thickness to avoid shrinkage in stressed areas, and support validation through static pull and cyclic fatigue testing. Test fixtures, load profiles and acceptance criteria can follow your internal standard or the applicable regulatory requirement.
What non-destructive testing do you perform on safety parts?
We offer magnetic particle inspection on ferromagnetic grades and dye penetrant inspection on all materials, at 100% or to an agreed AQL, with acceptance criteria defined in the control plan. Radiographic or ultrasonic examination of critical sections can be arranged where your drawing calls for it.
Do you supply heat-treated 4140 swivel bases?
We do. We cast 4140 and arrange quench and temper heat treatment to your specified hardness and tensile range, supplying certified mechanical test coupons from the same heat. Hardness is verified per the control plan and results are reported in the PPAP documentation package.
Can you integrate the seatbelt anchorage into the casting?
Yes, integrating anchorages and stop lugs into the casting is one of the main advantages over fabrication. We cast the bosses and machine the threads to your torque and pull-out requirements. Cast-in features remove welds from the safety load path and reduce the inspection burden.
How do you control dimensional consistency across batches?
We use dedicated machining fixtures, in-process gauges and SPC on key characteristics, with capability studies reported in the PPAP package. First article, in-process and final inspection data are retained and traceable, and gauge R&R studies support the measurement system behind every reported dimension.
CTA
Share your seat swivel base drawing, load specification and annual volume with Wendy She at sales@cnsandcasting.com, or contact Wendy She on WhatsApp at +86-13777124360. Ningbo Ruican will return a casting feasibility review, validation plan and budgetary quotation covering tooling, samples and series production pricing.
