20211 Metric Female Flat-Seat Hydraulic Hose Fittings (Swivel Nut)

Metric female flat-seat hydraulic hose fittings are the swivel-nut end of the flat-seal system: a female metric thread that turns freely on the hose tail, so you can tighten the connection without twisting the hose. The 20211 series covers 27 part numbers from DN4 (-02) to DN50 (-32), with female metric threads from M10x1 to M64x2 and a flat sealing seat, designed for wire-braided hose. If your machine connects hoses onto male metric flat-face studs – or your assemblers fight hose twist on every install – this page gives you the full reference: dimensions, part numbers, the T-variant question and OEM options.

Why Choose These Female Flat-Seat Fittings

• Swivel nut that turns freely. The nut rotates on the hose tail, so the connection tightens onto the male stud without winding the hose or fighting the assembly position.
• Flat-seat sealing system. The flat seat mates with a metric male flat-face stud in the flat-seal family, with the seal element compressed between the two faces.
• The widest bore coverage in the range. From tiny M10x1 (DN4) control lines to M64x2 (DN50) return lines – 27 sizes in one series.
• OEM-ready. Laser marking, custom plating, material test reports and batch traceability, with both 20211 and 20211-T constructions available.

Standards and traceability. Threads are ISO 724 metric threads. The series follows the metric female flat-seat configuration used across the widely adopted Chinese 10-series hose fitting numbering system (the female companion to the flat-seal male stud ends). Fittings are designed to pair with wire-braided hose built to EN 853 1SN/2SN or SAE 100 R1AT/R2AT performance classes. Dimensional inspection reports and material test certificates are available for OEM gate checks.

Swivel Nut and Flat Seat: How This Fitting Works

Two features define this series, and both solve real assembly problems.

The swivel nut. The female nut is not fixed to the hose tail – it swivels. When you connect the hose assembly to a male stud on a pump, valve or cylinder, you hold the nut and turn only the nut, not the whole hose. That matters more than it sounds: a fixed female end forces the operator to twist the hose assembly as the thread tightens, which stresses the hose, the crimp and the seal, and makes routing harder. With a swivel, the hose stays exactly where you routed it.

The flat seat. The sealing face of this fitting is flat, and it is designed to mate with a metric male flat-face stud – the flat-seal family that includes the 10311-type male ends. The seal element (an O-ring or a bonded seal, depending on the port system) is compressed between the two flat faces as the swivel nut is torqued, which is why the flat faces must be clean and the seal element must be present. If your male stud instead carries a 24-degree cone or a 60-degree cone, this flat-seat female will not seal on it – the flat system and the cone systems are separate families.

20211 vs 20211-T: what does the T mean?

Rows marked with a T use a different nut and collar construction, shown on the manufacturer drawing, for the same thread and bore combination. Functionally both are metric female flat-seat swivel ends; the T construction is the version your drawing specifies for those sizes. Order the exact part number – with or without T – as printed on your drawing or the old fitting, and we will confirm the construction before dispatch.

Flat seat vs cone seat: a quick check for female ends

If the old fitting or the port is unclear, send a photo of the male stud it connects to – the shape of the sealing face decides the correct female series.

20211 Series Technical Specifications

Materials and processing

• Body material options: high-strength carbon steel (20#/35#/45# grades, cold-formed or machined) as standard; stainless steel 304 or 316L available for corrosive or wash-down environments.
• Surface treatment: zinc plating as standard; yellow, white or black zinc, zinc-nickel and Dacromet coating available for higher salt-spray requirements.
• Heat treatment: hardness and case depth are controlled per drawing to keep the thread, the seat and the nut fatigue-resistant; typical surface hardness range HRC 20-28 (confirm the exact code on your drawing or PO).

Full dimension and part number table

All linear dimensions are in millimeters. E = thread, DN = hose bore, A and C = lengths per the supplier drawing, S2 = swivel nut hex across flats. Part numbers ending in T use the alternate nut-and-collar construction shown on the drawing.

Full dimensioned CAD drawings are available on request so your engineers can verify every length and the nut construction before you commit a batch.

Working pressure: the honest answer engineers need

A crimp hose assembly fails at its weakest link, so the rating of a 20211 fitting depends on the hose you pair it with and the crimp quality. Wire-braided hydraulic hose in this size range typically operates between roughly 80 and 400 bar depending on bore size and construction (1SN or 2SN). Send us your hose specification and we will confirm the working pressure, burst margin and the recommended ferrule for your exact hose brand – the check is free and takes one message. For derating at elevated temperature, follow the hose manufacturer’s pressure-temperature curve, because the rubber cover and tube lose capacity above about +100°C.

Which Fitting Series Do You Need: 20211 (Braided) or 20212 (Spiral)?

The part number changes with the hose construction, because the barb geometry and the crimp parameters are different.

When in doubt, check the hose label: braided hose is marked 1SN, 2SN or R1AT, R2AT; spiral hose is marked 4SP, 4SH or similar.

Part Number Decoder and How to Order

The 20211 part number carries the whole specification, so purchasing can copy it straight into a PO:

20211 – 22 – 08

• 20211 = metric female flat-seat swivel series for braided hose
• 22 = thread nominal size (here M22x1.5 female)
• 08 = hose dash size (here DN12, 1/2-inch class bore)
• T suffix = alternate nut-and-collar construction for that size

Because one thread size can serve several hose bores, always quote both the thread size and the dash size. If you are replacing an existing fitting, send us a photo of the nut end, the hose side and the male stud it connects to, and we will confirm the matching part number the same day. This service is the fastest way to convert an unreadable old part number into a confirmed 20211 order – and it also tells you whether your connection is flat-seat or cone-seat.

Assembly Guide: Four Steps to a Reliable Crimp

These fittings are crimp-style hose ends with a swivel nut on the port end. Follow the four steps below on every assembly.

Step 1 – Cut the hose square. Use a sharp hose cutter or cutoff saw. A square, clean cut lets the ferrule grip the cover evenly. A beveled or ragged cut is the most common cause of pull-out failures.

Step 2 – Prepare the insert depth. Push the fitting tail into the hose until it bottoms firmly against the internal shoulder. The hose end must sit at the full insertion depth, not short, or the crimp zone will be wrong.

Step 3 – Lubricate and insert. Apply a thin film of assembly lubricant to the hose bore and the barb. Push the fitting in with a steady twisting motion until it bottoms out, then wipe away excess lubricant. Keep the swivel nut free of lubricant on its sealing face.

Step 4 – Crimp and verify. Crimp the matched ferrule with the hose manufacturer’s crimp specification. After crimping, always measure the crimp outside diameter with a caliper and compare it with the crimp table. The measured value must sit inside the allowed tolerance band. If it is out of tolerance, do not put the assembly into service – cut it off and re-crimp with a corrected setting.

Warnings: three mistakes that cause leaks and blow-outs

• Never mix flat-seat and cone-seat systems. This flat-seat female will not seal on a 24-degree or 60-degree cone male, even when the thread fits.
• Never forget the seal element. The flat faces seal by compressing an O-ring or bonded seal between them; without it, or with a damaged one, the joint leaks.
• Never put PTFE tape or sealant on the thread, and never use the swivel nut as a wrench handle to force a misaligned connection.

Typical Applications

The metric female flat-seat swivel appears wherever hoses connect onto male flat-face metric studs and the installer needs the hose to stay put while the nut turns:

• Hose assemblies onto pump, valve and cylinder ports with metric flat-face male studs
• Control lines from DN4 up to large return lines at DN50
• Machine tools, presses, plastic and die-casting machinery
• Construction, mining and agricultural equipment
• Hydraulic power units and general industrial hydraulics

Wherever the mating stud is a metric flat-face male, the 20211 series is the female hose end – and the swivel nut keeps your routing exactly where you set it.

OEM Customization and Quality Traceability

For equipment builders and large maintenance programs, the 20211 series can be adapted to your exact drawing and your traceability rules.

Customization options

• Thread and geometry: special threads, modified lengths and non-standard configurations machined to your drawing or to a sample.
• Surface treatment: zinc-nickel, Dacromet or other coatings for higher salt-spray grades; we confirm the achieved test hours for the coating you choose instead of quoting a generic number.
• Laser marking: your logo, part number and batch or date code laser-marked on the nut or hex for full field traceability.
• Material: stainless steel 304/316L versions for corrosive media or wash-down duty.
• Packaging and kitting: custom labels, barcodes, poly-bag or box quantities, and complete hose assembly kitting.

Quality documentation

• Batch number traceability: every order carries a batch code that links back to the production records.
• Material test reports (MTR) available for carbon steel and stainless batches.
• Dimensional inspection reports for OEM gate checks.
• Third-party inspection (BV, SGS or similar) can be arranged before shipment.

Samples and MOQ. Samples for stock sizes ship fast, and we keep low MOQs for standard part numbers so distributors can test the series without tying up capital. OEM programs can move to scheduled deliveries once the drawing is approved.

Packaging and Logistics

Standard export packing: fittings are individually poly-bagged or boxed to protect threads, sealing seats and swivel nuts, then packed in export cartons labeled with part number, quantity and batch code. Custom labeling, kitting and barcode requirements are available. Exact carton quantity, gross weight and CBM are confirmed on the packing list for every order.

FAQ

Q: What is a metric female flat-seat hydraulic hose fitting? A: It is a crimp-style hose end with a female metric thread and a flat sealing seat, fitted with a swivel nut that turns freely on the hose tail. It connects onto a metric male flat-face stud in the flat-seal system.

Q: What does the swivel nut do? A: The nut rotates on the hose tail, so you tighten the connection by turning only the nut. The hose stays where you routed it, without twisting or stressing the assembly.

Q: What is the difference between 20211 and 20211-T? A: Rows marked T use an alternate nut-and-collar construction, shown on the manufacturer drawing, for the same thread and bore combination. Order the exact part number your drawing specifies.

Q: What is the difference between 20211 and 20212 series? A: 20211 is for wire-braided hose (1SN/2SN or R1AT/R2AT) and 20212 is for spiral hose (4SP/4SH style).

Q: Which male stud does this fitting connect to? A: A metric male stud with a flat face in the flat-seal system, sealed by an O-ring or bonded seal compressed between the faces. It is not designed for 24-degree or 60-degree cone males.

Q: Do I need thread tape or sealant? A: No. The flat faces seal through the seal element. Tape on a straight metric thread adds nothing and can contaminate the system.

Q: What is the working pressure of these fittings? A: The assembly rating depends on the hose, the ferrule and the crimp quality. Send your hose specification and we will confirm the working pressure and the recommended ferrule for your combination.

Q: Can you make custom part numbers with my logo? A: Yes. We offer laser marking, custom plating, stainless versions and special dimensions, with MTR and batch traceability for OEM programs.

Order Today: Metric Female Flat-Seat Fittings with Confirmed Fit

Every 20211 metric female flat-seat hydraulic hose fitting in this range is made to controlled dimensions, inspected before packing and backed by batch traceability. Send us your hose type, thread size and a photo of the male stud it connects to, and you will get a confirmed part number, the right construction (with or without T), a delivery date and a quote within one working day. Request samples first and test the swivel on your own bench – turning the nut instead of twisting the hose is the fastest way to feel the difference. We make sure the fitting, ferrule and hose work as one leak-free assembly.