20511 Metric Female 24-Degree Cone O-Ring HEAVY-Series Hydraulic Hose Fittings (Swivel Nut)

Heavy female 24-degree cone O-ring hydraulic hose fittings are the heavy-series (H.T.) swivel-nut end of the DIN 3865 O-ring cone joint, built for the higher-pressure circuits that specify the heavy thread schedule. The 20511 female carries its O-ring ready in the 24-degree cone seat – with the correct heavy-series O-ring size listed on every part number – and connects onto 24-degree cone male studs of the heavy schedule. The series covers 19 part numbers from DN6 (-04) to DN40 (-24), female metric threads M14x1.5 to M52x2 mapping to DIN heavy-series tube sizes from 6 to 38 mm, designed for wire-braided hose. If your drawings specify heavy-series O-ring cone connections per ISO 12151-2 / DIN 3865, this page gives you the full reference: dimensions, the O-rings that actually match heavy cone geometry, part numbers and OEM options.

Why Choose These Heavy-Series O-Ring Cone Fittings

• O-ring already fitted in the cone seat. The 24-degree cone carries its heavy-series O-ring, and the size is printed on each part number – no separate seal shopping at the bench.
• The heavy thread schedule. DIN heavy-series threads, M14x1.5 for a 6 mm tube class up to M52x2 for 38 mm, for the higher-pressure systems that specify them.
• The forgiving O-ring cone joint. The O-ring does the primary sealing with metal cone backup, tolerating surface wear that a bare metal cone joint would leak on.
• Swivel nut that turns freely. The nut rotates on the hose tail, so the connection tightens onto the cone stud without twisting the hose.
• OEM-ready. Laser marking, custom plating, material test reports and batch traceability, with replacement O-rings available.

Standards and traceability. Threads are ISO 724 metric threads. The sealing geometry follows the 24-degree cone with O-ring per DIN 3865 within the ISO 12151-2 hose-fitting standard – the O-ring cone configuration widely known in the trade as the DKOS-type joint, in its heavy (H.T.) schedule. 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.

Heavy vs Light O-Ring Cone Females: Not Interchangeable

The O-ring cone joint exists in two thread schedules, and they are easy to confuse because some nominal thread sizes look similar:

• Light series (L.T.), the 20411-type female. Light threads such as M22x1.5 for 15 mm tube or M30x2 for 22 mm tube.
• Heavy series (H.T.), this 20511 series. Heavy threads such as M22x1.5 for 14 mm tube, M24x1.5 for 16 mm tube or M30x2 for 20 mm tube.

The schedules step their tube sizes differently, so the same nominal thread (for example M22x1.5 or M30x2) appears in both series but belongs to different tube classes and different port envelopes. Order the female end from the same schedule as the male stud: heavy male stud, heavy female – light male stud, light female.

The O-ring is different too. Because the cone seat geometry differs between schedules, the O-ring that matches a heavy female is not the same size as the one for a light female at the same nominal thread. Two examples from the tables:

That is why every 20511 part number lists its own O-ring size, and why substituting a light-series O-ring into a heavy female, or fitting a light female onto a heavy male stud, produces a leak. If you are not sure which schedule your male stud belongs to, send a photo of the stud, the thread pitch and the old nut – we will confirm the matching 20511 part number, including the correct O-ring.

20511 vs 20511-T: the nut construction question

As on the other female swivel series, the -T suffix marks the alternate nut retention construction shown on the manufacturer drawing. Both constructions carry the same O-ring-equipped cone seat. 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.

O-ring cone vs plain metal cone females (20511 vs 20511C)

The heavy schedule also exists as a plain metal-cone female (the 20511C-type multiseal construction). The two heavy females look alike at a glance but seal differently: the 20511 seals through its O-ring with metal backup, while the 20511C-type seals metal-to-metal on the bare cone. Match the female to the joint type your male stud is designed for – send a photo of the stud when in doubt, because a metal-cone-only male may not seat correctly against an O-ring-carrying female, and vice versa.

20511 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 cone seat and the nut fatigue-resistant; typical surface hardness range HRC 20-28 (confirm the exact code on your drawing or PO).
• O-ring: NBR as standard for mineral oils; FKM available for higher temperatures and aggressive fluids. O-ring sizes per part number in the table – these are the heavy-series sizes, not the light-series sizes.

Full dimension and part number table

All linear dimensions are in millimeters. E = thread, DN = hose bore, Tube O.D. = the DIN heavy-series tube size sharing this thread and cone geometry, O-ring = the seal supplied with the fitting (as printed in the catalog), A and C = lengths per the supplier drawing, S2 = swivel nut hex across flats. Rows ending in T use the alternate nut retention construction.

Full dimensioned CAD drawings are available on request so your engineers can verify every length, the cone seat and the O-ring groove 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 20511 fitting depends on the hose you pair it with and the crimp quality. The heavy schedule is specified where the circuit or the port standard demands it – typically the higher-pressure classes of the size range. Wire-braided hydraulic hose in this range commonly operates from roughly 80 bar (large bore) up to 400 bar (small bore 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 and check the O-ring material limit for your fluid temperature.

Which Fitting Series Do You Need: 20511 (Braided) or 20512 (Spiral)?

The part number changes with the hose construction, because the barb geometry and the crimp parameters are different. For spiral-reinforced hose (4SP/4SH style), order the 20512 series instead, as 20512-XX-XX. Check the hose label before ordering: 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 20511 part number carries the whole specification – thread, bore, O-ring and construction – so purchasing can copy it straight into a PO:

20511 – 30 – 12

• 20511 = 24-degree cone O-ring heavy-series female for braided hose
• 30 = thread nominal size (here M30x2, DIN heavy-series class for 20 mm tube)
• 12 = hose dash size (here DN20, 3/4-inch class bore)
• O-ring = O16.3×2.4 supplied with the fitting
• T suffix (20511-30-10T) = alternate nut retention construction

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 cone stud it connects to, and we will confirm the matching part number – including the correct heavy-series O-ring – the same day.

Assembly Guide: Four Steps to a Reliable Crimp

These fittings are crimp-style hose ends with a swivel nut and a pre-fitted O-ring 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 O-ring and the cone seat clean and free of grease.

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. 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 the heavy and light schedules. A heavy-series male stud needs a heavy-series female, and the light-series O-ring at the same nominal thread is the wrong size for a heavy female.
• Never mix the O-ring cone joint with the plain metal cone joint. A male stud designed for a metal-cone female may not match the O-ring geometry of this nut, and vice versa.
• Never put PTFE tape or sealant on the thread, and never force the swivel nut when the cone is not aligned – the O-ring seats cleanly only with a straight approach.

Typical Applications

The heavy-series O-ring cone (DKOS-type) joint is specified on higher-pressure European-standard systems and on equipment that demands the heavy thread schedule. Typical duty includes:

• Hose assemblies onto heavy-series 24-degree cone O-ring male studs on pumps, valves and cylinders
• European-specified machines and their global service networks
• Machine tools, presses and injection molding machinery
• Construction, mining and material handling equipment
• Hydraulic power units and general industrial hydraulics

Wherever the mating stud carries a heavy-series 24-degree cone O-ring joint, the 20511 series is the female hose end – with the heavy-series O-ring already in place.

OEM Customization and Quality Traceability

For equipment builders and large maintenance programs, the 20511 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.
• O-ring material: FKM or other elastomers to match your fluid and temperature; O-rings supplied fitted or loose per your line-side process.
• 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, O-rings and cone seats, 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 heavy-series female 24-degree cone O-ring hydraulic hose fitting? A: It is a crimp-style hose end with a female metric thread and a 24-degree cone seat carrying an O-ring (DIN 3865 / DKOS-type joint), built to the heavy (H.T.) thread schedule. The O-ring is supplied with the fitting.

Q: What is the difference between the heavy and light series female O-ring cone fittings? A: The schedules step their tube sizes differently, so the same nominal thread can belong to different tube classes, and the cone seat and O-ring geometry differ. A heavy male stud needs a heavy female (20511); a light male stud needs a light female (20411).

Q: Is the heavy-series O-ring the same size as the light-series O-ring at the same nominal thread? A: No. For example M30x2 takes O16.3×2.4 in the heavy series but O20.0x2.0 in the light series. Each part number lists its own matched O-ring.

Q: What is the difference between 20511 and 20511-T? A: The -T version uses an alternate nut retention construction, shown on the manufacturer drawing. Both carry the same O-ring-equipped cone seat. Order the exact part number your drawing specifies.

Q: What is the difference between the O-ring cone and the metal cone heavy females (20511 vs 20511C)? A: The 20511 seals through its O-ring with metal backup. The 20511C-type multiseal female seals metal-to-metal on the bare cone. Match the female to the joint type of the male stud.

Q: What is the difference between 20511 and 20512 series? A: 20511 is for wire-braided hose (1SN/2SN or R1AT/R2AT) and 20512 is for spiral hose (4SP/4SH style).

Q: Do I need thread tape or sealant? A: No. The O-ring in the cone seat does the sealing. 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, O-ring material options and special dimensions, with MTR and batch traceability for OEM programs.

Order Today: Heavy-Series O-Ring Cone Female Fittings with Confirmed Fit

Every 20511 heavy female 24-degree cone O-ring hydraulic hose fitting in this range ships with its heavy-series O-ring, 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 cone stud it connects to, and you will get a confirmed part number, the correct O-ring, a delivery date and a quote within one working day. Request samples first and test the swivel on your own bench – the O-ring cone seats cleanly and holds under vibration. We make sure the fitting, ferrule and hose work as one leak-free assembly.